The Stovebolt Site Forums The Shop Area Engine Shop 1/2 ton rear end vs. 3/4 ton rear

has anybody every swoped out a 1/2 ton rear end and put in a 3/4 ton rear end on there 3100 series truck. ive got a guy that has offered to give me a 3/4 rear end out of a 54 or 55 chevy or gmc, not sure which.
it would be the open drive line then. it is the axe and pumpkin, springs and drive shaft. I know it would be 8 lug but i can deal with that.
will it swap ok. the problem with mine is i need a new tranny and i have 3 4 speeds sitting around. i've got the 3:90 ratio in the rear not sure what the 3/4 ton is. might be 4:10. i'm needing new or different leaf springs on mine as it sits to low in the rear even with out anything it it. the heavier leaves would help if mine are shot.
what do you think.

The 3/4 rear is most likely 4.57 or possibly 5.14.
Very slim chance it's 4.10, only if someone swapped in
a late 60's early 70's unit.
You don't say what year your truck is.

my truck is a 54 chevy 3100

Probably not your best option.

The brake drums have been hard to get though apparently the 3/4-ton ones are now being reproduced.

The 4.57 gears will limit your highway speed.

You should be able to find another axle that is a better choice if you are committed to a change. It sounds like you're changing the rear because you need to change the transmission. An open drive type SM420 can be converted to torque tube type easily and that might be your most direct solution.

You could use the pumpkin from a 55-59 chevy 1/2 ton with your axle, and get the open driveline. Of course there is some welding involved, but you would be doing that anyway.

how do i convert and open drive type sm420 to a torque tube?

Change the tail housing. I've not done it, but know a guy who did. All he did was unbolt parts from one and bolt them on the other.

I just had a guy call me a couple days ago and said he had a 4 speed with the tail housing out of a 50 or 51 about 10 miles from me. he said it was in good shape when he pulled it. what do i need to look for when i'm looking inside it. what might need to be replaced if anything from sitting. hope to get over to look at it this afternoon if the snow lets up.

Be sure to get the 4-speed's u-joint and keep your 3-speed's u-joint. You'll need to use the appropriate yoke from each one.

and if i can't get the u-joint where do i get one?

I think I got mine from Bruce Bugay in Glen Allen, VA 23059 Phone 804-752-6036

bwbugay@aol.com