88-98 GM Truck Rear End Experts Wanted

You're welcome.

Off roaders can break pretty much anything.  They get one tire wedged between two slickrocks and another 3 feet off the ground while in low range with a 10x torque multiplier going through an air locker and 37" tires.  Then they start tipping and stab the throttle and stuff breaks.  The other thing is, they might be 30 miles from phone service.  They tend to go overkill.

You are also correct on your thoughts about welding your axle.  A spool on the street sucks.

It has been a while since I built a truck 10 bolt, but don't despair about your wheels.  Given the thousands of combinations GM did, it is highly likely you can stuff your axle shafts in a new axle to keep your wheels.  I'll try to think of this off the top of my head, bolt patterns came in

5-lug: 7.5, 8.5, 9.5
6-lug: 8.5, 9.5, 10.5
8-lug: 9.5, 10.5

So, for instance, if you're replacing an 8.5" axle with another 8.5" from a GMT400, chances are (if they're the same width) you could stab your axle shafts in it to keep your current wheels.  There was a change from 28 spline to 30 spline, but I think that occurred before 88.  Put it this way:  chances are if you get an axle that doesn't have your current bolt pattern, I'm sure you can find a set of axle shafts that DOES have your bolt pattern.  GM did a lot of  that wheel bolt pattern swapping.  From the factory, they used the same shafts, just drilled for 5, 6, or 8 lugs on the flange.

Good info there, Curtis. The truck 8.5/8.6" did switch to 30 spline before 1988, so no problem there.

From working on my 1993 GMT 400 3/4 ton, the 6 lug axle was the 9.5" semi floater, with a standard axle flange. I don't believe the axles interchange with the 8.5/8.6". The 8-lug was the 10.5" full floater, so no changing the bolt pattern on it. Part of the fun I dealt with redoing the brakes, GM had a light duty and heavy duty 2500, 6-lug on LD, 8 on HD. I didn't find any instances of a 10.5" rear with less than 8-lugs, but knowing GM anything is possible. There is a lot of good info on rear ends on Pirate 4x4.

Dad's 88 2500 was a six lug on a 10.5"  I had a 98 8-lug on a 9.5"  They weren't picky.  You are correct in that most of the axles correspond with wheel bolt patterns, but not always.  I would say 70% of the time?

Axle shafts won't interchange between families, and will only interchange within the same family if you're certain of length.  It shouldn't be too difficult to find the right lug pattern already drilled to stab in an 8.5"

GMT800 trucks even had an HD1500 that has an 8-lug 10.5.

Bought this today for 75$ Canadian, which is about 14 cents usd. It was from a 95 z71 truck. Was told it’s posi and 3.73 haven’t pulled the cover to confirm.

9.5" semi floater.  Good score.

.. but it's more like 25 cents.