Technical Best rear diff ratio?

Your car is light which will help but how much compression ? Low rpm and high loads and high compression = detonation. New stuff gets by because of knock sensors if you hook up a real time scanner to your newer vehicle you be surprised how much time the timing is retarded..

 

It depends on what ratio the five-speed is. Don't focus just on the fifth gear. If you use a low ratio rear, let's say 370, it may work well in fifth gear, but, depending on the trans ratio, your 1st and 2nd may be too low. I run a 325:1 with a 30 inch tire in my '37 Chevy and it works great! My trans came from an '83 or so Camaro, so you can look up the ratio for that. On the other hand, my son used an S-10 5-speed and the 325:1 rear is way too low ( ratio) in his Model A. Also a 30 inch tire.

 

Which S10 T5? There are two common ratio sets.

 

3.70 gear is most practical for this general application

 

I have a 392 in my '32 Roadster with a world cl*** T5 out of an '88 Trans Am.
29.5 inch tall rear tires and a 4:10 9'' Ford rear end.
Fifth gear is really good above 50 mph, 4th gear gets a little long in the tooth above 50 mph.
At about 65mph I am turning around 17-18 hundred rpms.
There is so much torque, and so little weight that is just fine.
KK

 

Wasn't this standard 6-8th grade curriculum stuff

 

I like the red gears the best.

I think that I read somewhere that not all 5 speeds were OD transmissions, but it may have been in a books the accuracy of that information is not the same as if I had read, it on the web.

Unless the hemi is built to the hilt it is not going to be a revver. If all I was going to do is drive it and the transmission is 1:1 final drive the 3.5:1 gear is what I would choose. If the transmission is an OD I think I would lean toward a deeper gear, in the 3.7-4.1 range. But all of this is moot if my guessing about the build is way off.

 

Well maybe not, educators are responsible for this.
The masters and Ph.D. level idiots drew it up, accepted and printed this in education curriculum materials.

Then city engineers liked it too I guess.

 

Vicky you are gas my friend....

 

I've heard that before, but recall the pronounciation with a silent "G"

 

My '32 sedan runs a 327, T-5, Ford 9", and 29" tall rear tires... so not too different from your setup. I ran 3.89 gears for about a year, then swapped to 3.54 and never looked back. The 3.89s were obviously snappier, but first gear was too short for normal around-town driving (for my tastes). The 3.54's are perfect. My sedan does great in the city and cruises all day long at 75 mph at an honest 20 mpg.

As others have said, the OD ratio in T-5's can vary quite a bit, so apples-to-apples is tough without more details... but just wanted to p*** along my experience.

 

I forgot this was the H.A.M.B

I should've said "Crunch some numbers"

 

The difference is cruising only or needing some peppy acceleration.

 

I have an '88 T-5 trans with Astro Performance gears, a Ford 9" with 3.25 gear like Bob's in my '32 sedan, with 29" tires. The car is 2700 lbs. and has a 385" SBC with 490 torque at the rear wheels. It cruises at 2500@80. It's about as good as it gets!

1st gear is 2.95
4th is direct
5th is .78 OD.

I don't know how much torque a .060 over 392 makes, but I'll bet it would be just fine with a 3.25 gear.

 

I agree the 4.11 with a 5 speed and 30" tires is perfect . Lugging it pushing air at 70 mph with a 3.50 or 3.70 is worse on milage and main bearing wear than a light throttle slightly higher rpm with the 4.11. Also easier on the clutch especially on hills.


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Need to know what kind of driving and ratios. More info. I have a 3:00 and 700 in one and a 4:11 and 700 in another. different purposes.

 

3.50 is a great all around gear

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