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Hi Guys,
I just bought a 57 chevy 3/4 ton and I am planning to use it as a daily driver during high school. It has a has a 235 6 cyl with a 4 speed granny low tranny. they were both rebuilt about 50,000 miles ago. For what I plan to use it for I need more speed. I dont need a drag racer but I want to keep up with traffic. Any suggestions on performance parts or maybe an engine swap where I wont have to change the tranny. Any suggestions will be greatly appreciated.

Dude, im not the only high school kid here, thats great. Unfortunately, I'm not as lucky as you, as I have a 89 F*rd for a pickup for highschool. But if you want it to keep up with traffic id strongly suggest a 327 or 350. But youd wanna upgrade front brakes to stop as well as the rest of the traffic.

Drew

Just swap the rear gears if you want more speed. An engine swap is a waste of money; it won't get you a significantly higher top speed with the same trans/diff combo and you'll have to re-invent the steering linkage.

Hi
you might think about a T5 trans. I believe some of the S10 ones fit with very little in modifactions. Try a search it has been a subject asked about several times. be careful about the trannys year models...
Brad

what Hedgehog sez - skip the motor swap - that ol 235 will cruise at 70 if the rear gears are right, but to change a 3/4T I think ya gotta swap the whole rear maybe - the T5 might work if ya can match the outfit spline

Bill

You might want to look into just changing the gears in the rear,I think GM used the same center section into the late sixties with better ratios. If thats the case a gear change will be easy.

The pumpkin is the same from 1947 to 1972. Apparently the 67-72 3/4T Auto trans trucks have a 4.10 rear that swaps in no problem. You don't even have to jack up the truck with the floating rear. Patricks makes a 3.90 rear, but you need the 67-72 carrier to mount them. I have the same problem with my 49 3/4, so I am looking for the 4.10 rear. Right now it's a 4.57. My neighbour (a furd high-truck guy) says the rear is very similar to the Eaton rears on some furds. I don't know if any parts would fit, though. Good luck!

Start checking local shops that do rear-end work. Like most folks say, you need taller (numerically smaller) rear end gears.

A motor swap is do-able, but tough - mounts and bellhousing must change, or else you have to do engine and transmission both. Not a bad idea, but $$$. Do keep an eye out for a wrecked/scrapped mid-50s truck with a V8 setup, but for now, try to get a 3.5-ish or so rear end ratio.
This will cruise nicely, but still pull well with that 4 speed.

Personally, I don't think a T5 would help much. It depends on what's in the axle now. 4.56 rear gears and a .9 OD is still pretty short gearing.....

Check out:

http://www.chevytrucks.org/tech/s10t5.htm

Cheers!
George

New engine + new tranny = same top speed! (Unless that tranny has an overdrive...)

Top gearing on most any transmission is 1:1, meaning for every turn of the engine the driveshaft turns once. If you swap the engine and tranny, the 1:1 ratio stays the same.

An overdrive transmission drives the driveshaft faster than the engine, so that is an option. I don't know if the T5 is such a tranny...?

Changing the "pumpkin" as suggested can also improve things. The 3/4 tons are geared slower to haul heavier loads, but with a lower top speed.

-Boyo

With the pumpkin swap, you will go from 4.57 to 4.10 gears, which will give you an increase of 10%. It's the easiest and most economical alternative. If you can't find a pumpkin locally, try Tom Myers at 525 15th place, S.W., Miami OK 74354, phone 918-542-3871.

Another option is to go to a later model differential. There are a lot of 14 bolts with 3.73 gears, some even have 3.42s. You will have to measure from outside drum to outside drum, and find one that's close to yours. Weld the spring perches and shock mounts from your old one, get the right u-joint and you're ready to go.

Putting in a bigger engine will get you up to speed faster, and the V8 will turn higher rpms than the 235, but you're better off to regear the truck first. I wouldn't put an S10 tranny in a 3/4 ton on a dare, they're just not strong enough if you haul a load.

I have a 52 3/4 ton pu with a 57 235 motor and the sm420 transmission. Having recently added front disc brakes (5 bolt), I put a nova rear end under the truck to have the same bolt pattern all around. Since I use it as a daily driver here in the Alabama hills and haul few loads, which would be a better rear gear setup, a 3.73 or 3.42? According to the rpm calculator there is only 200 rpm difference between the two in fourth gear (1:1). I can find plenty of 3.73 sets in the S10 pu's around here but have not been able to find one of 3.42. Should I hold out for the 3.42 or will a 3.73 do just as well on the highway?

Bill Pratt

Thanks for all of your help. I think that I'm going to try and find a pumpkin somewhere around here and swap for 4:10 gears. Has any body here put a T-5 in a 3/4 ton? I would like to have more info on that swap. If I replaced the pumpkin with one from 67-72 then could I re gear that pumpkin for 3:38 or 3:55 gears?

I had a 52 1/2 ton with a 261. I replaced the stock trans with a T-5 from an S truck....cost me about $1500 and it made all the difference in the world....highly recommend it