Driveline angle questions with Speedtech components

[cpd004]

I have a 71 Firebird with Extreme front sub frame. It has an Ls3 and 4L60e.

I recently had some issues with the original 10 bolt and ended up getting one of their 9" axles.

The rear has their torque arm setup.

There is no way at all to measure the bearing cap of the front U joint as Spicer suggests. Best I could do was at the harmonic balancer face as they list in their Mopar instructions I happened to come across.

I am using a Klein digital angle finder. It is a small square device.

At the balancer, I see 2.8 degrees down. There are several shims between the trans and the trans mount. There is no room to go any higher at the tail of the trans if that's what is needed.

The driveshaft actually runs upward at 1.0 degree.

The center section has approximately 4 washers as shim and runs upward at 1.1 degree.

Their instructions at section 4 on page 20 ( https://speedtechperformance.com/wp-content/uploads/2022/11/Torque-Arm-20300-1.pdf ) say this:

Pinion angle should be within range at the ride height as stated above. If you feel a drive shaft vibration at
speed, you may need to adjust your driveline working angle. We have found this to be at optimum on our
ExtReme products between 1.5-2 degrees. Use shims on either the rear pinion mount as seen in the diagram
70-81 F-Body Torque Arm Page 21
below or at the transmission crossmember until you have the correct angle and any driveline vibrations should
go away.
We have found that in all our installs we have not need to adjust the pinion as it is engineered into the mounts



Not sure how they don't find a need to run them at the center between that mount and the torque arm because mine would point down without these washers.

That would both the trans and center pointing downward. Many websites say this is not acceptable.

I do have an email out to them. The initial email mentioned removing shims at the trans. This doesn't seem correct at all.

I do have the old subframe setup with the very thin tube trans crossmember. Not sure if this has anything to do with anything, but like I said, I can't go any higher with the trans to reduce that downward slope.

[srode1]

I would call them - they are very responsive every time I have called with a question. It's a lot easier and faster to have a conversation than back and forth emails.

[dontlifttoshift]

Can you clarify this?

The driveshaft actually runs upward at 1.0 degree.

Actually, if you clarified all of your angle measurements as either up or down in the rear it would ensure accurate math. I am assuming that these measurements are taken with the rear suspension loaded.

If the driveshaft is running uphill to the rear end, your working angles are 2.1* in the rear and 3.8* in the front.

[cpd004]

Had a little bit of time to try again. The car is on its wheels which are on the 2x4 cribbing that are homemade and then those on rolling dollies. The car has been bounced around on these to hopefully settle it as much as possible. It appears as though it's at ride height but elevated.

Took out the shims at the back between the pinion mount and torque arm.

So this is what I am seeing:

At the crank hub = 3.0 degrees down

Driveshaft = 0.9 degrees up

Center section = 0.9 degrees up

If I'm understanding this correctly now, 3.0 + 0.9 = 3.9 for working angle 1

0.9 - 0.9 = 0.0 for angle 2

So this is far from their 1.5 to 2 degree no noise/vibration suggestion. The zero at the rear is not acceptable at all. The rear can be rotated.

The options I have are to go lower at the trans increasing the downward slope and/or going up at the pinion. A lot would have to be reworked to lift the trans and reduce the slope there.

Maybe I'm misunderstanding something.

The reason I began looking into this is that I have a weird harmonic sound that seems like it comes from the driveshaft off throttle as it coasts down while testing it. The center section builder immediately asked about driveline angles. So looking them over is where I am.

[dontlifttoshift]

Based on that information, you're math is correct.

If you roll the pinion down, working angle at the trans becomes less and working angle at the pinion becomes more.

If you go up on the pinion, angle at the trans is just going to get worse.

[dhutton]

I could be wrong but I think you either need to raise the transmission or increase your ride height.

Don

[cpd004]

That's what I was worried about. There is definitely no way to go up at the trans as of right now.

The tunnel is tight and would likely have an issue with the trans dipstick, lines, the exhaust is rigid, etc.

I'm not 'as low as I can go' IMO. Speedtech says their subframe is engineered to have 5" of clearance from center cradle to ground. It's been a while since I measured, but I believe I was closer to 6.5"

I'll call them again.

All of that bolted in without issue so I'm not sure where the problems are. I have an early subframe. The trans cross member has been redesigned since then and is not interchangeable.

[cpd004]

This is where we are after back-and-forth emailing.

I sent them pics of the exhaust clearance, motor mounts and trans mount. Now they are saying I need to cut the tunnel out and raise it! I bought this subframe because it required NO cutting or welding of any kind to run the engine and trans I had.

After that, in addition to the 4 below and one above the trans mount, I have to add an additional 1/2" of shims!!

[dhutton]

This is where we are after back-and-forth emailing.

I sent them pics of the exhaust clearance, motor mounts and trans mount. Now they are saying I need to cut the tunnel out and raise it! I bought this subframe because it required NO cutting or welding of any kind to run the engine and trans I had.

After that, in addition to the 4 below and one above the trans mount, I have to add an additional 1/2" of shims!!

The whole tunnel or just under the transmission?

[cpd004]

Just the trans portion.

[dhutton]

Just the trans portion.

Speedtech sells that T56 tunnel which can be installed with screws etc if you don’t want to be welding on your car.

[ADY]

Speedtech sells that T56 tunnel which can be installed with screws etc if you don’t want to be welding on your car.

Installed this on my '68 that has a SBC and T56, I did the cutout with the finished interior, so welding wasn't an option and used 3M panel epoxy (https://a.co/d/2VjFGlq). Pain in the ass...yes, wish I had a garage that wasn't built to barely fit a 1920's car.

[cpd004]

Speedtech sells that T56 tunnel which can be installed with screws etc if you don’t want to be welding on your car.

I see first gen tunnels. Not second.

I went with the 4l60 because they said a 6l80 would definitely require mods. I would’ve much rather had the 6l80.

[dhutton]

I see first gen tunnels. Not second.

I went with the 4l60 because they said a 6l80 would definitely require mods. I would’ve much rather had the 6l80.

Sorry. I’m stuck in first gen mode. It can likely be adapted to fit a second gen.

[cpd004]

The reason I went with the 4l60 is because Speedtech said with that trans, I would not need to modify the tunnel like I would with the 6l80 that I preferred.

I was willing to go with that trans to avoid any tunnel work.

A CV driveshaft isn't recommended by two different shops I asked to hopefully avoid the angle issue. Both said the weight would cause transmission damage due to this.

[TBART70]

Did you ever figure this out?

[cpd004]

Sort of.

Donny (in this thread) took care of the tunnel and corrected the angles.

The car feels much better with my limited drive time-hopefully much more in the coming weeks.

Unfortunately, the noise (whine, hum, etc.) is still there. I believe it's slightly quieter but definitely not gone.

The noise is the most annoying part. Some background on the axle/center section:

Dutchman originally supplied the rear axle as specified by Speedtech:

It’s a 31 spline Eaton TruTrac with 3:70 gears, nodular iron case, aluminum Daytona style pinion support.

Everything went together easily and without issue. Upon driving it, it immediately exhibited and increasing in volume hum upon accelerating then decreasing as it slowed. The noise is not affected by trans gear and is by vehicle speed.

I contacted them and they asked that I send the center back. I did and they couldn't find anything wrong but changed the gearset to anther ratio (at my request) and brand. No change.

Dutchman and Speedtech claimed there should be no noise. The previous 10 bolt had none. The only change was the complete rear axle assembly and driveshaft. PST made the shaft. It was also sent back to be rechecked which yielded no issues found.

Dutchman kept blaming the transmission. The noise seems to be behind me and not under nor in front.

Researching lead me to John's Industries. I contacted them right at their acquisition time by another company. They were willing to look at the rear and suggested a different gearset. Off it went for a new gearset and rechecking of everything. Back it came and no change in the noise.

I kept asking if we could swap out the TruTrac and warranty it as nothing else affected the noise. Dutchman refused and claimed TruTrac's can never go bad nor make any noise. Never is a strong word and my luck with this car likely makes that improbable.

Strange is local to me somewhat. I decided to ask them about the center and if they could take a look at it.

They also swapped gearsets and a couple of other parts. They could not swap the TruTrac as a warranty claim and did not find anything wrong with a physical inspection. Back in it went and little to no change.

When I described the noise to Strange (and later Moser who I saw at a car show) they both blamed the solid mounted torque arm set up and more often than not, inherently noisy 9" rears. Both called it a tuning fork suggesting swapping either to another rear or find a way to isolate everything with rubber. I'd like to try the rubber but there is no way that I can see without quite a bit of reengineering.

After the center came back from Strange, it went to Donny's shop (definitely recommend his place if you need any work at all) for the tunnel and angle work.

At this point, I'll try and live with it for now or eventually try one last thing-swap the TruTrac for a Wavetrac. The angles are now correct after the floor work but if this was going to be the case al along, I'd have much rather had the 6L80e than the 4l60e.

[TBART70]

Been chasing a similar issue with vibes and angles. What angles did you end up with? I tried pinion down, pinion up. Trans is down 3 degrees, drive shaft up 1 degree to the rear. Front of pinion up to the floor 2.5 degrees. Vibe is better but not gone. Triagulated four bar. Sucks to move pinion angle, because I have to put it on alignment machine to get it square again. I have a 9" with a locker in it. I had a TKO in it, put a TKX in it to raise up the trans from 4 degrees down. Didn't think I needed to do tunnel work when I built the car. 2.5 to 3 degrees down I thought was stock. Had some noise from the TKO, still have some from TKX, might be from the rear I guess.
Thanks for the response.

[camcojb]

Sort of.

Donny (in this thread) took care of the tunnel and corrected the angles.

The car feels much better with my limited drive time-hopefully much more in the coming weeks.

Unfortunately, the noise (whine, hum, etc.) is still there. I believe it's slightly quieter but definitely not gone.

The noise is the most annoying part. Some background on the axle/center section:

Dutchman originally supplied the rear axle as specified by Speedtech:

It’s a 31 spline Eaton TruTrac with 3:70 gears, nodular iron case, aluminum Daytona style pinion support.

Everything went together easily and without issue. Upon driving it, it immediately exhibited and increasing in volume hum upon accelerating then decreasing as it slowed. The noise is not affected by trans gear and is by vehicle speed.

I contacted them and they asked that I send the center back. I did and they couldn't find anything wrong but changed the gearset to anther ratio (at my request) and brand. No change.

Dutchman and Speedtech claimed there should be no noise. The previous 10 bolt had none. The only change was the complete rear axle assembly and driveshaft. PST made the shaft. It was also sent back to be rechecked which yielded no issues found.

Dutchman kept blaming the transmission. The noise seems to be behind me and not under nor in front.

Researching lead me to John's Industries. I contacted them right at their acquisition time by another company. They were willing to look at the rear and suggested a different gearset. Off it went for a new gearset and rechecking of everything. Back it came and no change in the noise.

I kept asking if we could swap out the TruTrac and warranty it as nothing else affected the noise. Dutchman refused and claimed TruTrac's can never go bad nor make any noise. Never is a strong word and my luck with this car likely makes that improbable.

Strange is local to me somewhat. I decided to ask them about the center and if they could take a look at it.

They also swapped gearsets and a couple of other parts. They could not swap the TruTrac as a warranty claim and did not find anything wrong with a physical inspection. Back in it went and little to no change.

When I described the noise to Strange (and later Moser who I saw at a car show) they both blamed the solid mounted torque arm set up and more often than not, inherently noisy 9" rears. Both called it a tuning fork suggesting swapping either to another rear or find a way to isolate everything with rubber. I'd like to try the rubber but there is no way that I can see without quite a bit of reengineering.

After the center came back from Strange, it went to Donny's shop (definitely recommend his place if you need any work at all) for the tunnel and angle work.

At this point, I'll try and live with it for now or eventually try one last thing-swap the TruTrac for a Wavetrac. The angles are now correct after the floor work but if this was going to be the case al along, I'd have much rather had the 6L80e than the 4l60e.

9" rears and aftermarket gears make noise. Some worse than others. It's why some guys are going the Ford 8.8 instead, trying to reduce the noise. If you can find a set of good Ford gears you'll likely get the best result regarding noise. I'm hoping mine is on the quieter side.

[dhutton]

I would take a look at Detroit Speeds 8.8 inch in 9 inch housing center section. I considered it for my 57 Buick wagon but decided to try a 9 inch because I already had axles. I think you need to change out one axle. Definitely worth a look imo.
https://detroitspeed.com/products/rear_axle/assembled_center_sections/

I’m sure Donny can offer some feedback on it.

[dhutton]

Been chasing a similar issue with vibes and angles. What angles did you end up with? I tried pinion down, pinion up. Trans is down 3 degrees, drive shaft up 1 degree to the rear. Front of pinion up to the floor 2.5 degrees. Vibe is better but not gone. Triagulated four bar. Sucks to move pinion angle, because I have to put it on alignment machine to get it square again. I have a 9" with a locker in it. I had a TKO in it, put a TKX in it to raise up the trans from 4 degrees down. Didn't think I needed to do tunnel work when I built the car. 2.5 to 3 degrees down I thought was stock. Had some noise from the TKO, still have some from TKX, might be from the rear I guess.
Thanks for the response.

I think any time you have the pinion higher than the transmission with the transmission pointing down it’s going to be a problem. That’s a classic example of when the transmission needs to be raised. Either that or raise the ride height.

[cpd004]

I don't have the final angles handy right now. Donny may be able to chime in. I don't believe I had a vibration. At least I didn't notice one. The harmonic noise is what I have. It's very annoying and sticks with you when you get out of the car. Through the three different gear sets (by manufacturer) in this car, none have made much of a difference in the sound. That's why I believe at least some of it has to do with the TruTrac. The only way for me to have anything done with that is to buy another and pay to swap it in. That's rather costly to just try. I still may. It's no fun pulling the 9" and even less putting it back in without damaging the Lube Locker gasket. I'd still like to try a WaveTrac.

I did look at the 8.8 but it would not be a direct swap due to the way the torque arm attaches to the case of the 9" in Speedtech's design. That would've definitely been something I would've rather went to as I'm a fan of it. I didn't ask Donny if he saw a way to do so without a lot of re-engineering. That and rubber bushings may help at least in theory.

Finding NOS Ford gears in a ratio other than a non-street friendly ratio is impossible. I have no interest in anything over 3.25 and would ideally like below 3.0 these days.

[dhutton]

I don't have the final angles handy right now. Donny may be able to chime in. I don't believe I had a vibration. At least I didn't notice one. The harmonic noise is what I have. It's very annoying and sticks with you when you get out of the car. Through the three different gear sets (by manufacturer) in this car, none have made much of a difference in the sound. That's why I believe at least some of it has to do with the TruTrac. The only way for me to have anything done with that is to buy another and pay to swap it in. That's rather costly to just try. I still may. It's no fun pulling the 9" and even less putting it back in without damaging the Lube Locker gasket. I'd still like to try a WaveTrac.

I did look at the 8.8 but it would not be a direct swap due to the way the torque arm attaches to the case of the 9" in Speedtech's design. That would've definitely been something I would've rather went to as I'm a fan of it. I didn't ask Donny if he saw a way to do so without a lot of re-engineering. That and rubber bushings may help at least in theory.

Finding NOS Ford gears in a ratio other than a non-street friendly ratio is impossible. I have no interest in anything over 3.25 and would ideally like below 3.0 these days.

It never occurred to me that it wouldn’t work with the torque arm.

[dontlifttoshift]

When we were done with the tunnel and raising the transmission in CPDs car, working angles were 1.2* front and rear. Thats about as ideal as it could be.

Before we raised the tunnel and the car still had the 10 bolt when we initially set up the torque arm, working angles also matched but we were a tick over 2* and it was a lot of work to get there with the torque arm as we needed the roll the pinion down to get there.

We did a FN88 in a 55 chevy. I purposely put a 3.70 in this one as that is notoriously the loudest 9" ring and pinion. Rear end is dead quiet, I was elated. There is no easy way to make that work with the SpeedTech torque arm, but it's not impossible. It would also need new axle as the center line of the differential is different.

Currently doing a 67 Camaro with a S197 8.8 and a quadralink. As I reassemble my car it is also geting a S197 8.8 and a quadralink. Also setting my car up with a Cortex torque arm so I can make some comparisons but that's a different thread.

[dhutton]

When we were done with the tunnel and raising the transmission in CPDs car, working angles were 1.2* front and rear. Thats about as ideal as it could be.

Before we raised the tunnel and the car still had the 10 bolt when we initially set up the torque arm, working angles also matched but we were a tick over 2* and it was a lot of work to get there with the torque arm as we needed the roll the pinion down to get there.

We did a FN88 in a 55 chevy. I purposely put a 3.70 in this one as that is notoriously the loudest 9" ring and pinion. Rear end is dead quiet, I was elated. There is no easy way to make that work with the SpeedTech torque arm, but it's not impossible. It would also need new axle as the center line of the differential is different.

Currently doing a 67 Camaro with a S197 8.8 and a quadralink. As I reassemble my car it is also geting a S197 8.8 and a quadralink. Also setting my car up with a Cortex torque arm so I can make some comparisons but that's a different thread.
Damn, I have 3.70 gears for my Buick 9 inch…. :bang:

[camcojb]

Damn, I have 3.70 gears for my Buick 9 inch…. :bang:

Don, hope you're one of the lucky ones that gets a quiet setup. While I'm at it I'm hoping mine are quiet too... :lol: :thumbsup:

[cpd004]

When we were done with the tunnel and raising the transmission in CPDs car, working angles were 1.2* front and rear. Thats about as ideal as it could be.

Before we raised the tunnel and the car still had the 10 bolt when we initially set up the torque arm, working angles also matched but we were a tick over 2* and it was a lot of work to get there with the torque arm as we needed the roll the pinion down to get there.

We did a FN88 in a 55 chevy. I purposely put a 3.70 in this one as that is notoriously the loudest 9" ring and pinion. Rear end is dead quiet, I was elated. There is no easy way to make that work with the SpeedTech torque arm, but it's not impossible. It would also need new axle as the center line of the differential is different.

Currently doing a 67 Camaro with a S197 8.8 and a quadralink. As I reassemble my car it is also geting a S197 8.8 and a quadralink. Also setting my car up with a Cortex torque arm so I can make some comparisons but that's a different thread.

The angles did seem to smooth things out somehow. At least that’s what I thought upon that first drive when it returned.

In my opinion only, it’s not just the gears. 3 different sets by 3 different manufacturers and 3 shops. Either they’re all no different from one another, this is just common with all torque arm 9’s and/or it’s that TruTrac. The only parts that did not go back were the axles. Nothing obvious was found there. I do regret not at least having them looked at.

The FN988 is around $2800 with associated parts last I looked. Plus new axle and the fab work would be an extremely considerable investment. I believe I’d need both axles as if I recall correctly I have 35 spline and not the 31 needed for the 8.8.


I’d be happy to offer the car as a test mule for development to adapt the 8.8 :)


Coincidentally all three shops found things they did not like as done by the previous shop when tearing down the center. I was hopeful each time one found the culprit.

[dhutton]

The angles did seem to smooth things out somehow. At least that’s what I thought upon that first drive when it returned.

In my opinion only, it’s not just the gears. 3 different sets by 3 different manufacturers and 3 shops. Either they’re all no different from one another, this is just common with all torque arm 9’s and/or it’s that TruTrac. The only parts that did not go back were the axles. Nothing obvious was found there. I do regret not at least having them looked at.

The FN988 is around $2800 with associated parts last I looked. Plus new axle and the fab work would be an extremely considerable investment. I believe I’d need both axles as if I recall correctly I have 35 spline and not the 31 needed for the 8.8.


I’d be happy to offer the car as a test mule for development to adapt the 8.8 :)


Coincidentally all three shops found things they did not like as done by the previous shop when tearing down the center. I was hopeful each time one found the culprit.

Based on everything I have read it’s the gears. They are all noisy. Just some worse than others. Your torque arm with solid mounts may be amplifying the noise.

[dhutton]

Would be interesting to calculate the resonant frequency of that torque arm. Last time I did that was 45 years ago in university. :)

[camcojb]

Would be interesting to calculate the resonant frequency of that torque arm. Last time I did that was 45 years ago in university. :)

You're definitely a brainiac Don... :lol:

[dhutton]

You're definitely a brainiac Don... :lol:

Ya no… :). I was navel gazing and wondering if the resonant frequency of the arm was anywhere close to the driveshaft or axle speeds. :)

We need a real engineer like Stielow to weigh in… :). Or Donny likely has an idea on this.

[cpd004]

Ya no… :). I was navel gazing and wondering if the resonant frequency of the arm was anywhere close to the driveshaft or axle speeds. :)

We need a real engineer like Stielow to weigh in… :). Or Donny likely has an idea on this.

Stielow is an FN988 guy as well in his latest build.

I believe they tossed around a few ideas at Donny's shop. Ultimately it would have been a trial and error and see what works thing. If he does think of something to try, I'd be all for it.

I would not go Speedtech for the rear again. Go Detroit Speed. The front is another story.

[cpd004]

Donny, if you have both the 9" and FN988 can you post a side by side? Interested in how much more aside from the pinion support would have to be made to swap the 8.8 into the Speedtech torque arm.

Are the bolting locations in the same place (distance) from base of the housing?

[dontlifttoshift]

https://cdn11.bigcommerce.com/s-pqjmdlht5a/images/stencil/1280x1280/products/8042/29226/51c07c812f6285fc7367209abd780bf3dfe1c3b9__41998.17 32293245.jpg?c=1

[TBART70]

That really sucks, I have a 9" with 3.70 gears, luckily I don't have any noise
. Looks like I might need to be in the planning stages for tunnel mods.
Thanks for the responses and info.
Hopefully you figure out the noise.