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junkyardjeff 11-19-2007 08:48 PM

Determining a decent ratio
I am putting a new driveline in my 37 chevy p/u,I am retaining the 235 but installing a S10 5 speed and modern rear end. The 5 speed has a 4 to 1 first gear and in 5th the output shaft turns 1 1/3 to one revolution of the input shaft so it looks like there is not much overdrive,I was wanting to use 3.73 gears but with the 4 to 1 first gear it looks like a little taller gear will be needed. It has 235/75 tires on the rear so would a 3.25 to 3.55 gears be a decent choice for what I have. Jeff

matt167 11-19-2007 09:15 PM

S10 T5 trans likely has a .72 ratio, but may have a .83 or .85 if your lucky, but these were more common pre 1985.

judging by the project 33 calculator, you'll be turning 1,725 RPM at 65 MPH in 5th. 2,549 RPM in 11st going 20 MPH.. with a 3.73

I'd say 3.73 would be a good choice but heres the calcs anyway

70 ElCam 11-19-2007 10:37 PM

You're going in the right direction with the 3:73s, as stated in the previous response. The question is if the 235 will pull the O.D. when combined with anything higher than that with the 235/75s you'll be running. As I recall mine liked to keep a little rev on it to pull hills good .

Nice calculator matt . :thumbup:

junkyardjeff 11-20-2007 04:12 PM

The only concern I have is with the 4 to 1 first gear in the 5 speed,I dont want first to be like a granny gear with the 3.73 gears. Jeff

speedydeedy 11-20-2007 06:33 PM

Go with 3.73 and if first is too low drive it like the old granny gear and take off in second.This will be like having an under and over drive for if ever you really need to pull or climb a steep hill.

31chevy 11-21-2007 07:56 PM

How much should i expect to pay for for that S10 5 speed. I a looking into it for my 32 chevy 3:73 rear end and 250 chevy engine . What year too

shortyforty 11-21-2007 08:44 PM

Here is a Excel speed calculator freeware I found that lets you play with a number of factors. Includes graphs of results.

Don't know if this link to it will work to download and save from.

junkyardjeff 11-21-2007 09:26 PM

I got my 5 speed for 75 dollars and I think there are three trans with different ratio spreads,the trans I have has a 4 to 1 first gear which might act like a granny gear with a steep gear. I am leaning towards a 3.55 gear for my truck instead of 3.73s then I woint need 5th around town. I have seen them priced all over the place so shop around. Jeff

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