The Stovebolt Forums Forums The Shop Area Driveline 1946 Rear End Whoas

Hello Experts, I have a 1946 Chevy with a 235 and a SM420 four speed. I'm swapping it to the S10 T5, but am hoping to keep my rear axle housing. I've read several posts talking about how its possible to use a third member from a 1955-64 truck, and it will bolt right in to where the torque tube enters. My issue comes in finding one. I have searched high and low online and the only thing that comes up are third members from cars. Even when I specify the search for truck third members, I get the ones for the cars. Am I missing something here? I can find a ton that say, "1955-1964 BelAir Corvette Impalla Third Member Rear Differential". They look like they will fit just fine. In fact the outside casting ribs even look the same as my current one. Does anyone know if one of these would work? Thank you in advance!

I have performed the swap using a 55-66 truck it is as easy as they say. I would start pavement pounding and putting out want ads. Get others looking for you. Someone knows someone who knows a guy... That is unless someone confirms the fit of a car member. There are piles of these trucks around. Talk to old farmers, mechanics, wreckers, and I’m sure you’ll find one in short order and likely for a song. Mine was free! The old farmer I visited had a junkyard of severely rusted/beat up iron and said to me, “Just be safe in there doing it, son.”

No problem, sir.


I got him a bottle of his favourite whiskey for his time. Free, but not so free. 😉

Good luck.

No, they won't fit. The 55-64 passenger car housing has an oval hole for the gear carrier housing, and the pickup housing is round there. There's also only a very slight difference in the gear ratio, from 4.10 to 3.90. You need to be looking for a 55-up PICKUP rear end center section, not a passenger car. You would also need to come up with a way to lock the rubber-bushing housing pivots at the springs to keep the rear end housing from twisting and damaging the universal joints. Welding them is almost impossible.

Depending on the OD ratio of the T-5 you choose, the 3.90 gear would be an excellent choice to go with. The extremely high gear ratios that are available from passenger car rear axles can be too much of a good thing, and can limit your use of 5th. gear to level ground and downhill. The laws of physics are not suggestions, and getting the engine RPM way below the torque peak will result in sluggish performance and lousy gas mileage.
Jerry

I have a 1954 3100 with a 1979 Chevy Nova rear end with 2.73 gears' You will have to redo the spring perches. The springs are wider. The gearing I have is not a problem. I live in flat land. But with T5 I have driven ok in the east coast mountains. BTW I have driven to KC 9 times over the past 12 years, no problem.

This is exactly what I needed. Thank you all! On the topic of the spring perches, I knew I needed to weld some new ones on the axel, but other than those and the ubolts is there anything else holding the axel to the frame? Maybe I’ve got something missing on mine currently, but the axel is only attached to the leaf springs and nothing else. What am I missing?

[quote=blud123] possible to use a third member from a 1955-64 truck, /quote]

'55 - '62, 1/2t rear axle change from 3rd member to 12 bolt integral housing in 1963.

The axle tubes are attached to the spring leaves, and nothing else except possibly the shock absorbers. As the axle housing and springs react to bumps in the road, they move as a unit. Torque tube axle housings have to pivot as the assembly moves in relation to the transmission, hence the flexible connection to the springs. The pivoting rear end mounts also position the wheels slightly off center in the rear fender openings. If you convert the housing to the weld-on rigid mounts that are available from various hot rod suppliers, the wheels can be centered in the wheel oprnings by reversing the spring leaves from their original position to put the spring center bolt in a different location.
Jerry

You will need to remove the pivots (or weld them solid) or install something like this as Jerry suggested:

In the second photo, you can see the old spring perch pivot cupping over from the front of the axle tube. Like Jerry said, a benefit of using a new spring perch is you can mount it 1” back to help center the wheel/tire in the fender opening. The new perch can be drilled off center to sit over top of the center spring pin.