VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Transmission Change

Hey all,
I am looking at possibly changing the transmission in my '38. I hear that some people are doing a Tremec T5 swap. I know, I know it isn't original to the car, but this car is a daily driver for me and I would love to be able to get it out on the freeways reasonably. Has anyone done this? Or can anyone point me in the direction of someone who has? I'm wondering how much modification is required to the floorboards and any other issues that will need to be addressed.

Thanks,
-Davis

There are plenty of changes required to use a T-5. To mate it to a torque tube rear end requires serious modification to either the back of the transmission or front of the torque tube or both. If you use an open drive shaft then you have to change the rear end spring mounts and modify the pinion to accept a universal joint and seal from water and dirt. Or you can change to a S-10 or other rear end and change the brake setup particularly e-brake, 6 to 5 lug wheels. If have left out a few details like brake and clutch linkage, floor boards etc. but the above will give a rough idea of the options/modifications required.

Davis,

You might want to ask your questions on H.A.M.B. and also on Chevytalk. Likey folks on both sites have done this mod. Someone on here may have this info but this Forum leans more toward original stuff.

Also, you will want to investigate your choice of a T5 tranny carefully. T5 gear ratios are all over the map, including the overdrive ratios (largely determined by the engine/vehicle a T5 came from). Ratio info is available on line (search T5 gear ratios). This info and the last 4 digits on the tag on the tranny/s will give you the actual gear ratios of a given T5.

You know its going to end up being more then a trans swap after you get started,along with the trans the rear end will have to be changed and if you want to keep the original wheels you are going to need a rear end with 6 lugs and then hook up the parking brake. I done it on my 37 p/u and converted to disc brakes up front and it took me all winter to get it done,it just depends on how far you want to go and if you want to keep it more on the original side I would look into a gear change in the rear end first.

Hi Davis,

Maybe you could get most of the desired benefits if you changed over to the 3:54 rear differential? Depending upon what ratio is in your car today that can make a big difference. This forum can provide more than enough guidance on that update.

In addtion to all the physical fit-up issues, you should also spend some time and confirm that you will gain what you expect. I assume that your primary motivation is to have a higher travel speed at a lower engine speed. The overdrive ratio in the T5 might make the engine run so slowly that it does not develop sufficient torque to pull the car without lugging at freeway speeds. The 216 engine had good torque and power numbers for that era but you cannot assume any similarities to the engines in today's cars.

Have fun with the project,
Rusty

"We are a nonprofit organization dedicated to the preservation and restoration of all years of Chevrolets." Just sayin'

Rusty, you hit the nail on the head with that post.

He may want to get a 261 and hook it to a 3:55 or so. Such a combination will get good speed down the highway and still retain the old look. I think the 261 will pull the taller gears more efficiently at higher speed than either the 216 or 235. On top of that you will get full pressure to the oil filter. Something that you will not get on either of the other.

Charlie

In '54 I had a '47 club coupe with a 3.55 and a really good 216. It was a fun-to-drive car. It was just a bit slow from a dead stop for the first few feet but otherwise, fine. It pulled the mountains around here like a champ. I enjoyed the higher speeds in low and 2nd. I wouldn't have gone back to the 4.11 "for any reason known to man".

As for T5 trannys, watch what you buy. Some of 'em have an overdrive factor of .83 and some are around .73. There is a chart on line that gives T5 ratios if you have the last 4 digits from the tag on the T5. T5 gear ratios are all over the map so they offer a lot of versatility if you are selective. It goes without saying that a T5 will require an open drive line.

What kills the power with a 3.73 0r 3.55 is putting the weight of 5 passengers in the car. Really kills the hill power. On my '39 you shift to 2nd gear on a steep hill compared the original 4.22 where you never down sifted. If I am in the car alone there is no problem.
And yes, it runs up in 1st and 2nd gear much better although starting in 2nd requires a little more clutch slipping.
Still a great change.

Thanks all I really appreciate the input. I'll look into a rear end first and go from there.

-Davis