Gear Ratio

[Swain]

What gears should I be running. I am going to be running a stock T56 6 speed in my 68. I just got my 9 inch housing and need to get my third member. What Ratio should I be running?

[Van B]

I currently have a 3:90. And am thinking about going to a 4:10.

[monza]

FUeL has 4:10 It's fun and maybe to fast out of the hole but who knows, 6th gear is pretty much useless, mellow high speed cruising.( mellow but very fast)

Here is a good post regarding it:
http://www.lateral-g.net/forums/showthread.php4?t=16752&highlight=4%3A10

[6D9]

Need more info!

Rear tire height?
Cam specs??

[Swain]

Not sure what size im going with in the rear, I am trying to pick out what wheel i still want to run and what size 18x12 or 19x12

I was thinking 4:10 as well

Thanks for the help

[GregWeld]

Not sure what size im going with in the rear, I am trying to pick out what wheel i still want to run and what size 18x12 or 19x12

I was thinking 4:10 as well

Thanks for the help

Think about this - Corvettes run 3:42's and six speeds

I'm running a 3:73 in a 427 small block - and Ford 9"

So agree with the above commenters - high 3's or MAYBE low 4's... There are websites that you can compare gear ratios - and speeds... and tire diameters... that might be somewhat helpful for seeing the speeds in each gear. I use Smokemup.com but that is a "pay" site.

It's not fun to have to shift out of 1st gear at 10 mph - which is 10 feet from letting out the clutch... I've had cars like that - it sucks.

Ask Mark or Charley what Mule and Jackass are using - and whether or not they like them?

[Vegas69]

Look at your intended application and normal cruise speeds in your daily driver and play with the calculators. You also need to take into consideration your engine. How large is the camshaft, what type of fuel delivery?

[Swain]

As for right now I have a 383 SBC but things can change I need to do some more research haha. The motors just a short block but I keep thinking of going to a BBC. Thanks for all the help guys I will keep you posted on what I figure out.

[GregWeld]

Swain --

I don't know how accurate this info is - but it's food for thought and some discussion with someone that knows a whole lot more than I do...

I was "told" that the best gear ratio for "street" driven cars is one that puts your RPM at Cruise speeds about 200 RPMS LESS than where your CAM starts to make some torque (not just some torque but where it's going to start getting with it).... as this will allow you to cruise just "off" this area of the cam and by just barely tickling the throttle - you start to hit a nice sweet spot. This is supposed to give good gas milage - but give you great throttle response.

I'm tossing this out - since you said you have a short block - but also that you might change to a BBC... so that CAM selection / torque RPM / Cruise RPM calc would be important and make a huge difference in the feel of the car.

So, as example - you have a Cam that is rated at 2000 - 6500 rpm... I'd figure I'd want to be cruising at 1800/1900 RPMS at ? 65mph? and calculate backwards from there using your tire diameter. Or build the motor - dyno it - and see where it starts making power?

[Vegas69]

I agree, you need to spec the motor and pick your tire size first.

[DOOM]

I was just going to post about this very subject. I just got off the phone with Strange . Mike in tech told me I should be going with a 4.30 with my 572 6 speed .I told him I was running 19's . Man I thought that was a high gear. Does this sound okay guy's???

[waynieZ]

Mario won't that make you shift out of first aweful quick .They have a formular (which I forget right now ) but with a 2.66 first gear and 4:10's It was already on the high end of the scale for being too short. Someone will know the formular.

[E.rodz]

food for thought what do you plan on using the car for ?do you plan on autocrossing?taking it on long road trips?weekend drag racing.thats the first ? the second is what motor and howmuch hp.tq.have had many cars with 411 gears and they work good for a auto but not as well for a stick you just have to shift to much and gas milage suffers bad.I would give up a little hole shot for some extra milage and drivability for the street.but an autocross car for a short track would be a different story.you might be at the top of your preformance level of that t56 and with a deaper gear you will put more stress on the tranny.and fry tires alot easier..I think greg is on track with his calculations need more info before gearing can be figured for your optimum fun factor.

[Vegas69]

Look at your intended application and normal cruise speeds in your daily driver and play with the calculators. You also need to take into consideration your engine. How large is the camshaft, what type of fuel delivery?

Man that's a good idea.....:rofl:

[Flash68]

I was just going to post about this very subject. I just got off the phone with Strange . Mike in tech told me I should be going with a 4.30 with my 572 6 speed .I told him I was running 19's . Man I thought that was a high gear. Does this sound okay guy's???


Damn! You're already gonna have traction issues I imagine with the 572... those 4.30s ain't gonna help! LOL

I would think 3.73, 3.90, or 4.10 tops.

[DOOM]

After I posted I talked to Frank and he has me down to a 355 .That sounds way better. 430 did'nt sound right..

[GregWeld]

After I posted I talked to Frank and he has me down to a 355 .That sounds way better. 430 did'nt sound right..

Mario -- You still need to KNOW - not GUESS - at the tire diameter... final drive ratio... (there are multiple ratios available!) and your desired cruise RPM's for the given combination.


For comparison sake using ASSumed numbers:

Using a 355 x 30 19 tire - and the final drive of the T56 (700 torque - 1st gear is 2.97) and a 3:55 rear end -- @ 2000 rpms your speed is 106 MPH

Nice - as long as you can get away with it!

Using all the above but substitute a 3:73 - you're at 87 MPH

Using all the above but substitute a 4:56 - you're at 71 MPH

Drop the cruise RPM's to 1800

Speeds would be 83 - 79 - 64

Raise the RPM's to 2200 - which is about where it probably should be...

Speeds would be 101 - 96 - 79

NOW HERE'S WHERE YOU CAN'T JUST GUESS.... IF you use the Tremec with the 2.66 First gear look what happens using the 2200 rpm cruise and same tires... There's almost a 20 mph difference!

3:55's -- 81
3:73's -- 78
4:56's -- 63

[DOOM]

Sorry for the thread hyjack Swain!! Greg I'm running a 345-30-19 tire..

[GregWeld]

Right! Sorry SWAIN!! Sheeeesh -- I have a bad habit of doing that! My bad!

Mario -- tire size is close enough for the purpose I was trying to demonstrate... a couple 10th of an inch diameter isn't going to change the basic tech session I was running there...

My point was really more about how critical - or really - about how much difference there is between all these seemingly 'simple' factors. Tire size - final drive ratio - desired cruise RPMs.

A buddy has a 454 bbc Imagine Injected 56 Chevy with 3:55's and a 700r4 -- My 56 runs a 427 sbc 700r4 with 3:73's... I can hear the difference and I like mine better... and I've ridden in both (DOH!) and my 3:73's seem to put a little more bounce into the step. Would I like something in the 4:10 range? NO WAY... Do I care about gas milage? NOPE! I do like to drive my stuff - but also want relatively snappy performance so life is a trade off. :>)

[GregWeld]

Swain and Mario --

I just read the other post about gearing and Frank makes some very good points. This also brought to mind the recent Optima Challenge - it was so "obvious" which cars could actually put the power to the ground... they were MUCH quicker! The cars that just went up in smoke off the line... looked cool... sounded good... made lots of "furry" but went nowhere in a hurry. I've always referred to my tire size as my "slow blow fuse"... my car doesn't hook for poo... with the 3:73's... and too narrow tire... guys love it - and I'm not going to change 'em - and would need major mods to get more tire under it... With a motor that throws down torque like a 572 - mid 3's should get 'er done! And maybe a 5 speed instead of the 6?

[Vegas69]

Come on Greg, that's what traction control is for. That would be your left and right foot on the clutch and gas. :D I wouldn't want a deeper gear in my car. I run a 3.73 with a tko600 and it's about right. 1st gear is plenty short and traction is a huge issue if you don't slip the clutch or modulate the gas pedal. It also allows me to run all my autocrosses in 2nd gear and not need to shift. Which version on the t56 are you running Mario?

[GregWeld]

Come on Greg, that's what traction control is for. That would be your left and right foot on the clutch and gas. :D I wouldn't want a deeper gear in my car. I run a 3.73 with a tko600 and it's about right. 1st gear is plenty short and traction is a huge issue if you don't slip the clutch or modulate the gas pedal. It also allows me to run all my autocrosses in 2nd gear and not need to shift. Which version on the t56 are you running Mario?


WELL THAT SETTLES IT -- We both run 3:73's -- so then -- so should everyone else!!

LOL

Hard to modulate my torque converter... and I wear magnetic shoes and the floor is made of metal. It'll hook up when it gets done spinning!! :rofl:

[awr68]

I will be using a 3.89 with my SBC-T56-9"-335/30/18 combo. I should be at 1800 rpm @ 65mph

[DOOM]

Come on Greg, that's what traction control is for. That would be your left and right foot on the clutch and gas. :D I wouldn't want a deeper gear in my car. I run a 3.73 with a tko600 and it's about right. 1st gear is plenty short and traction is a huge issue if you don't slip the clutch or modulate the gas pedal. It also allows me to run all my autocrosses in 2nd gear and not need to shift. Which version on the t56 are you running Mario?

Todd I have'nt worked out my trans choise yet:_paranoid I'm going to get with Frank and have a little pow wow about this . I want the strongest and the best........ I know that much....

[Vegas69]

:willy: That's a pretty important step before you choose a gear. :rofl:

[DOOM]

:willy: That's a pretty important step before you choose a gear. :rofl:

I no I no :unibrow: