The Stovebolt Site Forums The Shop Area Driveline 3 spd to 4 spd on a 235

Hi everyone, getting ready to start working on my '49 - 3100 and wanted to know if anyone has swapped an original 3spd column shift with a 4spd floor shift (overdrive, non-granny)
I have a closed shaft 4:11 and am willing to change out the rear with a late model open shaft rear with a 3:73 if that is the best combination. Rear wheels I am thinking of using are 225/60R15
Basically, I'm looking for something that will get decent rmp's at 70mph, and can squirt around city traffic ok. I have read several posts that mention the 235 can't push a 5spd o.d., or it will get torn up, and I'd like to get it right.
I may mess with intake and exhaust to coax a few more ponies later, but am thinking of keeping the 6 rather than go with a v8.
Any help would be appreciated!
Mark

You have a lot of stuff going on here and perhaps some mis-understandings. There is a 4 speed overdrive transmission used in some later Chevy trucks and some Mopars. I can't remember the model but from what I have seen they are quite costly.
Many on this site are using T-5 OD transmissions and they work just fine. Lugnutz has a good write up on the care and feeding of T-5's. They can also be costly. Much of this is dependent on what your skills are and what you have to pay others to do.
The old tried and true BW OD trans from 55 up cars/trucks (SM319) is also a good option. It would of course require an open driveline and you would retain the column shifter. It's the closest thing to a bolt in.
Something you have to take into account is the brakes and steering. You can make just about anything go 70+ mph but you have to think about how you are going to stop it.
Fred

The 4 speed overdrive was the MY6, and was a GM bolt pattern version of the Chrysler A833 4 speed. The GM version isn't very common.
You may want to consider a different tire size. The 225/60/15 is only about 26" tall, much shorter than the oem tire. While it would be ok for acceleration, that diameter tire will kill the speed unless you gear it real high. A 225/70/15 would be better.

Thanks for the info. I didn't realize tire size made that much difference. I'll look at a 28" diameter tire now. Measured my stock bias ply's and they measure at 28".

Just looked at lugnutz website... Great info! I can't wait to get this thing running.

Sulli,

If you want to go 70 MPH in an AD truck, you should start thinking about brakes! What you gonna use?

Hi Sulli,
Nice to see a guy from Houston. Please be mindful of all aspects of your front suspension and especially the caster angle and toe-in. The 1949 truck steering is a decent enough design, but if you study it, you'll see it was designed to let the truck handle easily at low to medium speeds using tall and thin tires. I'd suggest experimenting with different caster shims to find what you like the best. Caster isn't something that is carved in stone...you have leeway, but you don't want it to be too little or zero. Also make sure somebody didn't do anything cute before you got the truck...count the number of leaves in your front springs (should be 8), make sure caster shims are still there and make sure your rear wheels are not taller than your front wheels (that will reduce the angle, also).

Jon

About going 70 in an AD truck, I'm about to install a bolt in IFS with discs, so I'll be covered for stopping ;-). I originally wanted a 4 link rear to go with the IFS, but found that the stock closed shaft won't work with the 4 link geometry, so I am thinking mono leaf springs and lowering blocks. My thought is that this set up will give me flexibility to run the stock 3 speed and rear for a while, and if I change to a T5, I can keep the same lowered stance, but would need a differential and driveshaft.
I'm a newbie who's been looking at my truck in the garage for a year, researching what I want to do, making lists, saving money, wanting it lowered and running, and looking to you guys for advice. I bit off quite a chunk with the ifs and hope I can pull it off. Gotta get a new master cylinder to work discs/drums, and had no idea that I'll need to modify the steering shaft/linkage as well.

You might want to reconsider the ifs front and look at a dropped axle along with a disc brake converstion.