1971 Chevy Suburban Redux

A chronicle of the rebuilding and rebirth of an American classic &mdash the
1971 3/4 ton Chevy Suburban.

May 12 2010

New Rear-End with Highway Gears

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Figuring out where to get some momentum on this project has been tough. I am really eager to get to the body work, but I think if I’m going to be a little practical, I’ve got to address some other things first.

First place to start… the rear ends (front and rear ends that is… the axles). Currently the ol’ ‘71 Suburban has an Eaton HO72 rear end, and a Dana 44 axle in the front. They’re supposed to be bulletproof 3/4 ton axles, but they’re geared for a mud-truck or for serious pulling. I’m making an honest to goodness SUV here, that needs to spin at decent RPMs on the highway, so 4.11 or 4.56 gears just wont do.

I found a guy locally that had a complete set, GM 10-bolt front and 14-bolt semi-floater rear, and they’re geared perfectly — 3.23. He lives just around the corner, so I drove the Suburban over to pick them up, and we wrestled the 400lb monsters into the back.

Getting them out of the truck and into my garage was a trick, but it’s done. I got the rear set up on jack stands and started to work.

There didn’t appear to be any leaks at the axle seals, which was a good sign, but it was clear the the brakes are totally shot, so I’ll have to deal with that soon. But first I wanted to get at the guts of this rearend, so I pulled the cover off and drained the gear oil (and I do love the smell of gear oil… don’t judge me).

GM 14-bolt open diff carrier

After draining the oil, I pulled the carrier out to inspect all the parts. Generally, there’s not much metal in the oil or stuck to the magnet at the bottom of the case. The bearings all look smooth — no nicks or scratches or gouges on the surfaces, and they roll smoothly. There appears to be no wear on the ring and pinion gears… so all of that’s a positive thing.

14-bolt rear end parts dismantled

After disassembling the diff. carrier I inspected the gears more closely, and noticed a major problem. The spider gears are toast! Big chunks missing, gouges and pitting on the surfaces. The side gears look good, which is strange, but the spider gears will have to be replaced.

busted spider gear

None of the local parts stores carry the spider gears for the 9.5″ GM 14-bolt rear end, so this week I’m in the hunt for either some good used ones, or I’ll have to buy a complete kit with the spider gears, side gears, washers, etc.

With that out of the way, I wanted to move on to cleaning and coating the axle housing with some POR-15. Before doing that I took some measurements to compare this 14-bolt rear-end with the Eaton HO72 that’s in the truck now. Unfortunately… another problem. The spring perches on the 14-bolt (this is from an 84 Chevy pickup) are about 1.5″ too far outboard, and the shock mounts are all wrong, the position and the placement.

I measured out the new positions and got to work cutting the spring perches and shock mounts off the axle. Below, you can see the left-side shock mount already removed, and marks for the new position of the spring perch.

Here’s the left-side spring perch welded into its new position:

This job was time consuming, so I didn’t end up getting to cleaning and coating, but I did get both perches and shock mounts relocated. The below graphic shows the before and after:

This week I’ll find some new spider gears and start collecting brake parts. Hopefully next weekend I’ll have the rear end done and bolted up. Can’t wait to try the 3.23 gears vs the 4.11 (or 4.56, haven’t confirmed one way or another) gears of the HO72. I’ll keep you posted.

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