59 GMC Rearends

[BigDan3131]

So what's the deal, I have read conflicting info saying its this or that or if it has this part then its that rearend. So...was the Spicer rearend found most commonly in 59 GMC trucks?

In any case how much power can the stock rearend handle? No drag racing no sticky tires just a nicely built 6.0L.

1959 GMC 1/2 Ton Fleetside Longbed.

[1project2many]

In any case how much power can the stock rearend handle? No drag racing no sticky tires just a nicely built 6.0L.

I think your real question is "Can the rear end live with this engine?" I say yes, it can. Mild driving, truck unloaded most of the time, absolutely. I put a 455 Buick into a '79 Monte and kept the 7.5" rear underneath it until the car hit well over 250k. The axles wore out from mileage but the rear was still good. No holeshots, no spinning one tire in sand, even a few runs at "elevated" speed. No problems.

The stamped housing of the 1/2 ton truck is a weak link just as it was with the cars. The big block cars used to pull the RR axle tube forward and could actually pull the frame in and buckle the floor. Like any drivetrain part, sudden shock like clutch / neutral dumps can do a lot of damage in a hurry so it's just common sense to avoid this unless you like changing parts. As long as the bearings and axles are good to start you should be fine for a long time.

[OrrieG]

I tried to destroy a lot of 60's rear ends as a kid, found the weak link was usually the universal joints. Only rear end I hurt was from low fluid when a seal went bad at speed on a long trip. Remember they were designed to work with a loaded bed or towing, I assume you will be relatively light loaded most of the time.

[BigDan3131]

The only thing in the bed will be a custom 32 gallon tank and maybe a custom spare mount as well.

[Red Foreman]

Here's a picture of the Spicer 45 thats in my 56 GMC to help you distinguish the difference between the GM rear axle.