Brake rotor centering [Archive]

WSSix

01-06-2018, 04:29 PM

Thanks guys. That's what I was expecting you to say.

I found that my rotor bores are at 2.78 inches and the axle hub is 2.68 inches. This cased the rotors to drop down onto the hub when putting everything back together. I thought I was locking the rotors in eccentrically and this might be the cause of my vibration. So I got some shim stock, put it between the rotors and hub register to tighten up the slop, and that did squat to help the issue. I was so fed up I just parked the car. For all I know, the shim stock didn't stay put some how but I doubt it since it felt the exact same. Maybe I'll look at it tomorrow.

Randy, I talk about the issue in the last few pages of my build thread. There are also other threads I've started concerning the issue. If you do a search for threads started by me, I'm sure it'll come up. The simple answer is I start vibrating at 55mph and up. It's at its worst at 55-60. It's speed related not engine or rpm related. It's definitely the rear end area, confirmed via dyno, and the wheels are true, confirmed via Wheel Wizards a rim straightening company here in Atlanta. Literally, nothing I have done has had any affect on it positively or negatively. It's maddening.

Thanks

carkrazy1987

01-06-2018, 07:16 PM

WSSix

01-07-2018, 03:43 AM

unfortunately rear end vibrations can be a number of issues. u-joint angles, wheel tire combo, brakes, axle itself.

you said you had the rims checked, was that with tires installed (good balance)?
rotate the wheels front to back if possible?
double check all drive line angles.
if you do believe it is brake related, can you safely put rear on jack stands (weight of vehicle on axle) and accelerate to 55-60mph, see if vibration there. then slowly start removing parts and retesting. remove wheels, install lugnuts, torque to specs and check for vibration. remove rotors (ziptie block of wood in caliper not to blow out pistons), and see if vibration still there.
if still there, vibration maybe within axle, or drive shaft.

also vibration is worse between 55-60mph, does it dissipate or get worse with more mph? if the vibration intensity is matched at 110-120mph you would be looking at u-joint area for binding

I appreciate the response. I've checked all of those components multiple times. That's what is so frustrating, nothing changes with any of my adjustments. It's not on or off throttle dependent either only speed.

I've put the car on jack stands before but the vibrations were minimal compared to on the road. I put the car on a dyno to verify it was the rear area of the car for that reason.

Thank you

GregWeld

01-07-2018, 07:04 AM

Check the following:

PINION ANGLE / Working angle

Driveline slip yoke - or more correctly - the length the slip yoke and it's engagement in the transmission.

WSSix

01-07-2018, 08:57 AM

Check the following:

PINION ANGLE / Working angle

Driveline slip yoke - or more correctly - the length the slip yoke and it's engagement in the transmission.

This is an area I think could/should be improved. I have a good bit of slip yoke engagement now, but to be more correct, I need maybe 3/4" more engagement. I wasn't wanting to just throw parts at the car, but I'm starting to get there because I'm seriously fed up and starting to look at E34 BMWs, lol.

Thanks Greg.

randy

01-07-2018, 10:28 AM

Did you get your driveshaft shortened?

Call up the driveshaft shop. They will build you a 3 1/2 aluminum driveshaft for around $450. This fixed my vibration issues the same ones you are describing. They are 1 of 3 shops in the US that balance the driveshaft high-speed. I have 1/4" slip yoke sticking out now past the t56 magnum dust boot.

I was getting vibration around 50 and it got alot worse 70 plus. Old steel driveshaft was double checked for balance and I couldn't figure it out. I did what unmentioned above and it fixed it. Also ask for the antivibration dampened option.

SSLance

01-07-2018, 11:40 AM

Really does sound like the drive line vibration issue I chased...which I finally fixed with a 3.5" steel driveshaft. My car originally came with a 2.5" shaft and the drive shaft shop said they wouldn't build a 54" driveshaft in anything less than 3.5"...said they'll "noodle" at speed if not big enough diameter.

Hope you find it...I hate vibrations...

ProTouring442

01-07-2018, 12:51 PM

WSSix

01-07-2018, 01:39 PM

You're running BMW wheels, yes? The wheels should be mounted "hubcentric" (indexed on the hub), and given the difference in bolt pattern between GM and BMW...

Know anyone with a set of GM wheels you can borrow?

I have hub and wheel centric adapters from Motorsport-Tech/BORA to correct the bolt circle and hub diameter differences. I've also removed the adapters and bolted the wheels directly to the car since the bolt pattern difference is very minor. There was no change in the vibration even though I could only center the wheel using the lugs.

Did you get your driveshaft shortened?

Call up the driveshaft shop. They will build you a 3 1/2 aluminum driveshaft for around $450. This fixed my vibration issues the same ones you are describing. They are 1 of 3 shops in the US that balance the driveshaft high-speed. I have 1/4" slip yoke sticking out now past the t56 magnum dust boot.

I was getting vibration around 50 and it got alot worse 70 plus. Old steel driveshaft was double checked for balance and I couldn't figure it out. I did what unmentioned above and it fixed it. Also ask for the antivibration dampened option.

Yes, factory driveshaft was shortened back in 09 when I did the LT1/T56 install. I had a good, local company do the work. I didn't have the vibration issue until 2014. Shaft length was perfect until I put the new suspension on the car. That raised the rear a little which caused the length needed to change. Problem is, I did more than just the suspension at one time. I also can't remember at this point if I had this vibration before I changed to the 3.90 gears which would change shaft speed. I also had other vibrations like tires being old and out of balance and a u-joint not perfectly secured that I found during my searching for a vibration solution. It seemed like I'd fix one thing only to realize it was only part of the issue. This current issue just won't go away.

I appreciate the insight. I was considering them or Denny's. I was also only considering steel since I'm no race car. I've had my drive shaft balance checked by multiple shops and it came back perfect each time. U-joints are good too which is why I say the yoke stick out is the only thing not perfect.

Really does sound like the drive line vibration issue I chased...which I finally fixed with a 3.5" steel driveshaft. My car originally came with a 2.5" shaft and the drive shaft shop said they wouldn't build a 54" driveshaft in anything less than 3.5"...said they'll "noodle" at speed if not big enough diameter.

Hope you find it...I hate vibrations...

I'm going to measure soon but I think I'm close to 54 inches. Maybe it's 45. I can't remember. It's the factory shaft with 3R u joints whatever it is. Plenty strong enough for the power and I don't run road courses so every thing I've read is it's fine to use. Maybe they disagree and can recommend a solution. I hate this vibration crap too. Love the power curve and drive characteristics but dear lord is this vibration ruinous to the enjoyment of the car.

Thank you all. I appreciate the responses and thoughts.

randy

01-07-2018, 02:26 PM

Get the 3 1/2" aluminum driveshaft, vibration reducer mod, and it will handle anything that you need. With the aluminum the critical speed was more than enough for what i was doing. Again 1 of 3 companys that do high speed balancing. The guy below is who i delt with. My buddy also had the same issue in his 69. Same issues as you and mine. Called the driveshaft shop and had one within 2 weeks as well and fixed his issue. My total length was 48 3/4". If you have a email i can send you a email with all that i delt with, measured etc

Lucas Bartholomew

The Driveshaft Shop
4530 Southmark Dr.
Salisbury, NC 28147
800-564-2244

WSSix

01-07-2018, 03:05 PM

Thanks Randy. I'll give Lucas a call.

WSSix

01-07-2018, 05:48 PM

I measured 48 9/16" so 48.5" I'm sure is what they'll cut it to. I confirmed again that I'm about 3/4" short now.

Thanks everyone

Che70velle

01-08-2018, 08:41 AM

Trey, I sure hope that a new shaft fixes the car. I have a relative in the driveshaft business, and maybe I can save you a buck or two if your interested? Send me a pm...

WSSix

01-08-2018, 05:04 PM

Me too, Scott. I appreciate the offer. I've already started working with Drive Shaft Shop. We'll see what happens.

Thanks

WSSix

01-09-2018, 07:26 PM

GregWeld

01-09-2018, 07:34 PM

I believe I've goofed on my working angles and I'm way over the 3* limit. I had always taken my measurements with the car sitting at ride height. Well, tonight I took them with only the rear off the ground and it became obvious to me that I think I screwed that math up. I'll see what Lucas at Drive Shaft Shop says in the morning.

Thanks

Easy enough to do ----

Motor should be about 2 to 3* DOWN at the tranny pan --- REAR END should be about 2* UP --- and if the slip yoke is correct (they make all kinds of lengths) -- you should be close.

The other thing I've seen --- a too small diameter drive shaft for the overdrive tranny / rear end gear combo. The shaft has a working RPM and when exceeded can go into harmonic death wobble. LOL

Glad you're on it.

WSSix

01-10-2018, 09:30 AM

Those values are actually pretty close to what I have for pinion angles now. The issue is my rear end if higher than the rear of the transmission so the drive shaft is down in front. The solution is to raise the trans more. I'm not sure I have the room due to my headers though.

I didn't want to get into it just yet as I'm waiting to see what the Drive Shaft Shop has to say, but I'm getting really concerned with some things about my build compared to what others have had to do with their similar builds. This whole car is a learning experience for me. I'm worried I may have missed or done some critical stuff wrong after all. We'll see what happens. I hope I'm just over reacting.

Thanks

GregWeld

01-10-2018, 09:34 AM

Ah -- yeah that won't work....

Tunnel issues with the new bigger transmissions --- and combine that with our low stances --- yeah --- that's usually a tranny hump mod and driveline tunnel raise....

Those are easy mods even in a done car..... it's a carpet issue --- and back seat tunnel modification...

WSSix

01-10-2018, 09:41 AM

I've already cut my tunnel once for the trans and don't mind doing it again. I'd like to do an integrated chassis brace and trans mount like DSE does while I'm there. I also don't mind doing the tunnel for the shaft as I have no interior now. It's the fact that many other people are running SBC/T56 combos in 2nd gens and aren't having these issues at all that concern me. Maybe I am just that low compared to them, but I'm concerned I'm doing a lot more than other's have had to do. That makes me questions what I've done wrong.

Thanks Greg. I appreciate the reply.

GregWeld

01-10-2018, 09:53 AM

Ah -- gotcha Trey.

Your motor only need be down 2* - and assume you have a degree / angle indicator.... The car needs to be on it's own 4 -- so jackstands under the axle so the weight in on it.... and place the angle indicator on the face of the pinion... if it's up 1 to 2*....

Then it's a matter of suspension travel.... and that's probably UP 2" and down 2" or in there.... and of course there should be a "bump stop" of some kind to prevent the stuff from hitting...

Che70velle

01-10-2018, 11:10 AM

Trey, my driveshaft is same way, higher at the rear than the front. A lot of guys with lowered vehicles are in the same boat...with no vibrations.
Driveshaft angle is irrelevant. You should see the angle of my brothers rear shaft on his 87’ truck. 17” of lift. It’s steep, and there’s no vibrations with 44” Boggers.
Engine/trans combo should be 2-3 degrees down. Even 4 is ok, I’ve done it. The trick is your rear must be up the same, whatever it is. These angles are also irrelevant of frame/chassis angle. Measure against shop floor, not chassis.
Are you using shims under the rear end to adjust angle? I’ve seen these shims not be exactly the same, and cause binding on the rear end housing when the u-bolts were torqued down tight. Angled lowering blocks can be the same way.
I know you’ve been all over this for too long now. Let’s hope the driveshaft change fixes it. DONT TORCH THE CAR!!!!

Vegas69

01-10-2018, 01:39 PM

WSSix

01-10-2018, 02:38 PM

The problem with the rear end being higher than the trans output shaft is that the working angles increase when the suspension compresses. So if you start out with a working angle of 3.5, under full compression it may go to 5.5.

This is exactly why you see people on here cutting their tunnel to get the tailshaft of the trans up higher. That will allow for more conventional and smaller working angles. The more severe the working angle, the more they tend to vibrate as speed increases.

This is what I'm thinking will end up happening. I'm just not sure I can raise the engine due to how close I built the headers to the floor.

I know a CV shaft has greater working angle capacity but I'm not sure it would be right for my application. I'll see what the information they come back with. I didn't hear from Lucas today. Maybe tomorrow.

Thanks everyone.

Vegas69

01-10-2018, 03:48 PM

Have you determined your actual working angles? I can't imagine a vibration around 60 mph unless your angles are very severe. Not in the 3-5 range. Normally is would get worse with speed with this scenario. Start to feel it around highway speed and increases as you speed up.

WSSix

01-11-2018, 05:02 AM

About 5.5 to 6 degrees, Todd. Unless, of course, I'm doing it wrong again.

With the whole car sitting on cribbing, I get 2.5 degrees nose up on the pinion, 3 degrees front down on the driveshaft, and 3 to 3.5 degrees down on the tail shaft.

Vibration doesn't get worse as I speed up, but it's still very obvious. The frequency may increase a little with speed though. Intensity does not.

Thank you

dontlifttoshift

01-11-2018, 06:15 AM

So your rear working angle is 5.5*

Your front working angle is 6 to 6.5*

It looks like this exaggerated drawing of passenger side view

pinion / \ / engine

You need to roll the pinion down.....a lot.

You will find if you set it up like

pinion \ _ / engine

you will be able to get working angles under 3* and then get them to match.

GregWeld

01-11-2018, 07:21 AM

AH --- actual real numbers to work with!! LOL

Donny is correct..... your working angles are a total mess.

I'm glad I got you to look at them. LOL

Vegas69

01-11-2018, 08:21 AM

Donny's numbers are correct. Those are pretty severe working angles for a performance car.

I don't agree that lowering the pinion will get you proper working angles though. From what you are saying, your driveline/pinion angle are within .5 degrees of each other on the same plane. As you lower the pinion, you will move away from parallel angles. It will decrease your working angles, but the variance in working angles from driveline to pinion will increase. Right now you have 5.5 and 6-6.5. Lowering your pinion will spread those numbers which can also cause vibrations. I'm guessing that if you drop your pinion 2 degrees to .5 up, your pinion working angle will go to 2.5 and your driveline to 5. I think your tailshaft still needs to go up to get conventional working angles.

While the angles aren't great, they are parallel and appear to be within .5-1. I think you may have something else going on since the vibration comes in at such low speed and doesn't get worse. You may have two things going on here. A driveshaft issue and then your working angles may cause you vibrations with speed. I'm no expert on this stuff, but I fought the same situation on my car. If I kept that car, I would've cut the tunnel and raised the tailshaft.

dontlifttoshift

01-11-2018, 09:37 AM

The driveshaft is running up from the transmission to the rear end, right?

If you roll the pinion down, the driveshaft also goes down in the rear, resulting in a lower working angle for both the front and rear u joints.

It's pretty hard to diagnose any vibration through a forum but the driveshaft angles are not good the way they are so it seems like a good place to start.

WSSix

01-11-2018, 09:46 AM

The driveshaft is running up from the transmission to the rear end, right?

If you roll the pinion down, the driveshaft also goes down in the rear, resulting in a lower working angle for both the front and rear u joints.

Correct, but as Todd mentioned, the angles are nearly parallel just in different planes now. I've always thought that was the correct way to have the pinion angle and transmission?

Thanks everyone

dontlifttoshift

01-11-2018, 09:57 AM

Forever the equal but opposite theory was the common theory that was regurgitated by magazines, driveshaft manufacturers, etc. and for most street rod swaps it worked. 3 degrees was the magic number, if you set everything there it would work and for the most part it did. But these aren't 40 Fords and the math doesn't work out.

The reality is that the u joint does not care about the angles on your pinion or your tail shaft and it especially does not care if they are parallel to each other.

All the U joint cares about is the angle that you are asking to work at.....and it wants to work at the same angle as the other U Joint. The lower the working angle, the happier the ujoint will be.

<iframe width="560" height="315" src="https://www.youtube.com/embed/gmV4qwLfOMY?rel=0" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

Incase embed doesn't work. https://www.youtube.com/watch?v=gmV4qwLfOMY

WSSix

01-11-2018, 11:45 AM

Thanks Donny. I'll watch the video when I get home. I appreciate the information.

Vegas69

01-11-2018, 12:38 PM

I ended up doing what Donny is saying on my car. Instead of cutting the tunnel I got my working angles as small as possible by lowering the pinion angle. I do think it caused an oscillating vibration over 85 on my car. The harmonics are no longer in sequence. It's certainly worth a shot.

If you have adjustable shocks, you could raise the car up as high as possible. That will effectively reduce your working angles and let you know if you are on the right path.

I agree though, 5-6 degrees of working angles is a problem regardless.

WSSix

01-11-2018, 06:31 PM

Watching the video Donny posted, they reiterate that the working angles need to be the same between the two u-joints while showing the working angles at each end being fairly extreme. Which is more important? I can rotate the nose of the pinion up more easily than bringing the tail shaft of the transmission up. That would get my angles the same between the two joints but the angles would be more extreme. I'd be simply doing this as a test to see if it effects the vibration at all.

I swear I've done this before and it had no effect on the vibration. Then again, I swore my angles were good, too.

Also, if I were to nose the pinion down 3.5 degrees to match the tail shaft, causing the drive line to look like this \ _ /, wouldn't that cause the drive shaft to become unstable or bind?

Thanks everyone.

Vegas69

01-11-2018, 07:00 PM

Your current working angles per your measurements are within .5-1 of each other. 0-.5 is ideal so you are close.

What you are describing with the pinion pointed down 3.5 is exactly what I just talked about. You are getting your working angles on both ends of the shafts as small as possible. It takes some trial and error. The problem with this strategy is that you may get an oscillating vibration. When the working angles are equal and opposite, you get a consistent hum or vibration, when they are not you will get a stronger vibration followed by none.

Equal and opposite and small working angles gives you the smoothest operation.

WSSix

01-12-2018, 05:30 AM

OK, I think I'm getting confused. I'm going to do some more reading and get back with you guys. I think I'm getting my terms mixed up or something.

Based on the measurements I have given, what is my pinion angle?

Thank you

randy

01-12-2018, 07:56 AM

Do this All angles are measured on the drivers side of the car.

1. engine/trans is on ____ angle and it heads down in the back. Meaning the crankshaft is higher than the tail shaft

2. The Driveshaft (if not there use a string or a piece of wood to go from the center of the output shaft to the center of the pinion) is at a ___ angle and it heads down in the back. The connection at the transmission & driveshaft is higher or lower than the connection at the rear diff to driveshaft. Does water from from the front driveshaft down to the rear or would it run from the rear to the front towards the engine

3. the pinion is at a ______ angle heads up or down in the back. The driveshaft and pinion create a V or a /\ ?. Would water placed on top of the diff run behind it or onto the driveshaft.

Base on this we will figure out the rest.

To give you an idea my angles were close but still caused a vibration and the aluminum bigger driveshaft fixed this. Mainly because the driveshaft was very level and caused a jump rope effect not to mention the driveshaft shop high speed balanced my new one.

Vegas69

01-12-2018, 07:56 AM

2.5 degrees UP from level.

Your tailshaft is DOWN 3-3.5 from level. If this is true it puts them close to the same plane.

This is exaggerated: Tailshaft: \ Driveshaft: / Rear: \

randy

01-12-2018, 09:10 AM

i just dont see his driveshaft going up from the trans to the rear diff. My car is Low and i know its a 1st gen but i still have 1 degree down on my driveshaft angle. If his driveshaft is going up my guess is that he is measuring his engine angle wrong. The crank pulley and fuel rails were the easiest spot for me to measure.

SSLance

01-12-2018, 09:51 AM

Trey, make sure whatever you are using for an angle finder is EXACTLY straight front to back for each measurement. It being just a bit off skew can really mess with the numbers.

And run to harbor freight and get a digital gauge if you don't have one already. The needle gauges are way inaccurate in my opinion.

WSSix

01-12-2018, 09:57 AM

2.5 degrees UP from level.

Your tailshaft is DOWN 3-3.5 from level. If this is true it puts them close to the same plane.

This is exaggerated: Tailshaft: \ Driveshaft: / Rear: \

Thank you. That's what I've been thinking and saying but the number of articles and information pages I'm reading that say the pinion angle is the difference between the drive shaft angle and the angle the pinion is placed at is staggering and it pisses me off, lol. It's just confusing me because in my mind the difference between the angles is the working angle not the pinion angle. Just wanting to make sure I'm communicating properly.

i just dont see his driveshaft going up from the trans to the rear diff. My car is Low and i know its a 1st gen but i still have 1 degree down on my driveshaft angle. If his driveshaft is going up my guess is that he is measuring his engine angle wrong. The crank pulley and fuel rails were the easiest spot for me to measure.

I measured at the balancer just a minute ago and it's showing 2.5 to 3 degrees up from level which causes the tail shaft to point down. I think I'm going to invest in a digital angle gauge so I can stop expecting this manual gravity one to be accurate. It's hard to read as well.

If you stand on the driver's side of the car moving from front to back, my drive line looks like what Todd posted \ / \ .

Thanks everyone

Vegas69

01-12-2018, 01:58 PM

The face of the U Joint is the best place to measure all the angles. I used a socket and angle finder, but a magnetic finder would be much easier as you could stick it right on the u joint.

randy

01-12-2018, 04:15 PM

Thank you. That's what I've been thinking and saying but the number of articles and information pages I'm reading that say the pinion angle is the difference between the drive shaft angle and the angle the pinion is placed at is staggering and it pisses me off, lol. It's just confusing me because in my mind the difference between the angles is the working angle not the pinion angle. Just wanting to make sure I'm communicating properly.

I measured at the balancer just a minute ago and it's showing 2.5 to 3 degrees up from level which causes the tail shaft to point down. I think I'm going to invest in a digital angle gauge so I can stop expecting this manual gravity one to be accurate. It's hard to read as well.

If you stand on the driver's side of the car moving from front to back, my drive line looks like what Todd posted \ / \ .

Thanks everyone

that makes no sense. the engine cant be angled up and the trans pointing down at the same time.

I have this one
https://www.amazon.com/Floureon-Inclinometer-Protractor-Magnetic-DXL360/dp/B00IKDQHV0/ref=sr_1_17?s=hi&ie=UTF8&qid=1515802449&sr=1-17&keywords=digital+angle+finder

WSSix

01-14-2018, 05:05 PM

Why not, Randy? The balancer is in front of the engine mounts which are a pivot point and the transmission is after the mounts. The tail shaft is slanted down at the rear and the balancer is slanted upwards.

Lance, your reply came in just before mine. I agree with the tilt of the gravity angle gauge. I always work to make sure I'm pointed straight down so that the pendulum swings and doesn't get pinned. There's an HF down the road. I'll swing by tomorrow I think.

I appreciate the replies. I was out of town all weekend so I haven't touched the car. Hope to get back on it soon.

Thanks

randy

01-14-2018, 05:36 PM

GregWeld

01-14-2018, 09:31 PM

Trey ---

One of the things that gets messed up is trying to make it too complicated....

And remember that you want the PINION angle DOWN -- because as the power is put to the rear end - it tries to rotate the pinion UPWARDS.... The type of suspension you have makes a difference in how much this is allowed to rotate from a "negative" to the positive. A race suspension which allows hardly any movement -- should be set about 1 to 1.5* Down (at the pinion).... and a rubber suspension would be 3.5 to 4* down - because it's going to rotate up A LOT.... Urethane bushings would be "harder" and can be set at 2 to 2.5* Down etc.

So you need to know the suspension set up and adjust accordingly.

The motor is going to be 3 ish * down at the tranny ----- and the diff should be set according to the appropriate down angle (allowing for it to climb back to about zero in hard launch mode) according to how much movement it should have (a little - moderate - or a lot) -- and the working angle of the driveline will mathematically work out to about 1 ish * (the angles should cancel each other out, but they should never be 0 ----- is should always have 1 to as much as 2 degrees "difference".

So let's say the engine is down 3* -- and the driveline is down from the motor to the rear end 4* -- and the pinion is down 2*

Use this calculator to help when you're measuring

http://spicerparts.com/calculators/driveline-operating-angle-calculator

WSSix

01-15-2018, 05:08 AM

The yoke is on the same plain as the crank shaft balancer. The engine if angled up the trans yoke is angled up. All of this is being over complicated.

Get the engine or tail shaft angle
Driveshaft angle
Rear pinion angle

And then you will have all the front and rear operating angles that you need.

This is why communicating properly is important and why I wanted to make sure we all understood each other. We're saying the same thing but we're looking at it differently.

To clarify, when I say the pinion is pointed 2.5 degrees up, I mean the nose is pointed up. The gear is pointed down. Using the link/calculator Greg posted, they consider the pinion to be sloped down.

Trey ---

One of the things that gets messed up is trying to make it too complicated....

And remember that you want the PINION angle DOWN -- because as the power is put to the rear end - it tries to rotate the pinion UPWARDS.... The type of suspension you have makes a difference in how much this is allowed to rotate from a "negative" to the positive. A race suspension which allows hardly any movement -- should be set about 1 to 1.5* Down (at the pinion).... and a rubber suspension would be 3.5 to 4* down - because it's going to rotate up A LOT.... Urethane bushings would be "harder" and can be set at 2 to 2.5* Down etc.

So you need to know the suspension set up and adjust accordingly.

The motor is going to be 3 ish * down at the tranny ----- and the diff should be set according to the appropriate down angle (allowing for it to climb back to about zero in hard launch mode) according to how much movement it should have (a little - moderate - or a lot) -- and the working angle of the driveline will mathematically work out to about 1 ish * (the angles should cancel each other out, but they should never be 0 ----- is should always have 1 to as much as 2 degrees "difference".

So let's say the engine is down 3* -- and the driveline is down from the motor to the rear end 4* -- and the pinion is down 2*

Use this calculator to help when you're measuring

http://spicerparts.com/calculators/driveline-operating-angle-calculator

Thanks for the link Greg. You're correct about over complicating it. What you've just posted is what I've always thought and worked towards. Until I started having problems that is. Then, I decided to learn more and ended up where I am now. :knokwood:

Luckily, I have 6* of angle shims under the rear so tilting the pinion nose down won't be hard. I'm going to remove the snubber/bumper on top of the transmission too so I can lift it a little more. We'll see where I can get the angles to go to from there.

Thank you all.

WSSix

01-15-2018, 06:09 PM

I went out and bought a digital angle gauge from Harbor Freight today. I verified it against a bubble level and my gravity gauge. I'm confident it's accurate within a couple tenths.

Pinion is 3 degrees nose up. Drive shaft is 1.5 degrees rear end up. Tail shaft is 3 degrees down.

Numbers are a little better I'd say but still not good enough if working angles are to be below 3 degrees.

I'm not sure why the drive shaft angle is less with the digital gauge. I put the gravity gauge right next to it and it went right back to the 3 degrees I measured the first time. I'm going with 1.5 degrees.

I'll adjust the angles in the coming days and see what happens.

Thanks

randy

01-15-2018, 08:00 PM

So driveshaft and pinion is in a /\?

If so dropping the rear pinion to neg 2 degrees should lower the driveshaft to closer to zero and maybe plus or minus .5 degree. If the driveshaft does go to a neg .5 them your front operating angle would be 2.5 and if rear pinion down neg 2 degrees it would make the rear operating angle 2.5 as well. Both operating angles would be equal if thafs the case

WSSix

01-16-2018, 04:53 AM

Correct. The drive shaft to pinion looks like /\.

I'm hoping to both raise the transmission and lower the pinion, but we'll see what I can come up with.

Thanks Randy

WSSix

01-28-2018, 02:09 PM

I lowered the pinion last weekend to the point that it's about .5 degrees nose down now. This got the working angle at the rear u-joint down to around 1.5 degrees. I was still slightly up in the rear. This did change the front working angle but it was still a little over 3 degrees. I took the car out for a drive anyway. Nothing changed or it changed so slightly it's not worth mentioning.

Today, I tried to raise the transmission by removing the snubber on top to gain the clearance I needed. I wasn't able to go up but a few tenths due to the reverse lockout hitting the tunnel now.

So my plan at this point is to cut the tunnel out enough to get the transmission where I need it. I'll leave it open until I'm certain I have the transmission where it needs to be. Hopefully, this will either fix the issue or allow me to rule it out.

Some maybe good news is I think I'll have the clearance I need for the headers though it will get tight in places once I raise the engine. I'm also fairly certain I won't have to raise the tunnel over the driveshaft. I'll just have to change the tunnel over the transmission.

The bad news and why I'm going to leave the tunnel open until I'm certain the angles are correct is that I'm going to have to cut out part of the factory tunnel brace that's spot welded to the floor from side to side. The drive shaft will be way too close if it clears at all once I raise the transmission. This means making a DSE style trans brace and putting in new floors which I needed anyway. I'm not willing to do all of that until after I know the drive line angles are working correctly.

We'll see what happens. I'll be back with an update later.

GregWeld

01-29-2018, 08:06 PM

Might not be an issue -- but if you have a rear sump -- don't get that up so much that the oil doesn't flow in to it..... ??? Maybe the pan is already sloped enough that it doesn't matter - I don't even know what motor you're running etc.

WSSix

01-30-2018, 09:59 AM

That's a good point, Greg. I'll check it soon to make sure I'm ok. The engine is still a Gen II LT1 though it is stroked. Thanks.

WSSix

02-03-2018, 10:57 AM

Finally! After all this time playing with this damn vibration issue, I have affected it with an adjustment. It's not fixed. It's better in some ways and worse in others, but it's in the drive line for sure. Hopefully, it's only the drive line and I don't still have multiple issues. I'll play with it more this afternoon and see what happens.

Thanks!

GregWeld

02-03-2018, 11:31 AM

Well ------ at least you're on to the cause. That's 90% of the battle.

Watch this video....
download this handy dandy phone app...... LOL it might help make setup easier.

OaVj6PtRewE

Che70velle

02-03-2018, 12:44 PM

Good news Trey! Interested in what you’ve found.

WSSix

02-04-2018, 06:29 AM

Thanks Greg. I'll take a look.

I raised the transmission up, Scott. Too much working angle in the front u-joint I do believe was the issue. At least that's what I was adjusting anyway.

Later in the afternoon I raised the nose of the pinion back up just a touch to see if that helps make things better as I had it about .5 degrees nose down. I haven't taken another official measurement but I should have the pinion .5-1 degree up now and the transmission 1.5 degrees down. The weather sucks today so I may not get it out to see if that helped make things even better.

Trans tunnel will eventually have to be removed entirely. I did that wrong way back in 09 when I first did the swap. I have the Hooker T56 tunnel piece coming. We'll see how that fits before I cut any more. If this works, I'm still confident I won't have to raise the driveshaft tunnel, but the factory brace in the floor I mentioned early does have to be cut for me to be happy with its clearance. It's really tight right now.

WSSix

02-04-2018, 02:46 PM

Well, the rain moved out early and the roads dried out enough that I could get the car out. It's even better than before so I'm getting closer. If this is the best it gets, I could live with it consider how bad it was before. I do still have some adjustments to make. I need to get it back up on the cribbing so I can get an official measurement to know where I am. The biggest issue I'm facing now is the car has a shudder that runs through it as I coast down from speed. Fairly certain this is pinion angle related for sure since I don't feel it going up through speed or while driving. I'll continue to do research and see where it leads.

Thanks for all the help everyone.

randy

02-04-2018, 06:11 PM

If you have vibration while deceleration the pinion might be down to far. Glad you are moving in the right direction. That aluminum driveshaft will help ALOT to get every bit of vibration gone

Che70velle

02-27-2018, 04:58 AM

Trey, how is this going? We’ve had a day or two without rain, so I know you’ve driven the car some.

WSSix

02-27-2018, 09:49 AM

Thanks for checking, Scott. I actually haven't touched the car. I'm also working on my friend's 69 mustang trying to get things done on it. I'll get back on the TA soon.

WSSix

06-09-2018, 06:13 PM

So I think I may have fixed the vibration today. I lifted the rear of the trans about half a degree and that seemed to do it. Not sure why as the last time I made an adjustment I had all my angles within spec when I measured without the driveshaft in place. I think the difference may be that I measured with the driveshaft in place this time and that showed that I was a little off from what I measured before. I would have though the measurements with the driveshaft removed would be more accurate since it allowed me access to the tailshaft.

Anyway, I'm going to work on closing the tunnel in now. I'll have to make a new transmission cross brace because the exhaust is almost pinned against it now. No big deal as I have to replace the floor boards too so it'll work out.