Making changes to a 10 bolt rear

[Leeztruk]

Gonna make this posting to see what you folks think. Been toying with a SF 14 bolt swap ( see recent post on axle swap), but this could be expensive on my limited income (I'm retired). So, what I thought of, is this. I have a 10 bolt rear from a previous C10 project ('86) that's complete, drum to drum, sitting on the garage floor. Checking on Rockauto, the drums from my '89 2wd Cheyenne have a height of 3.6". The '86 drum is the same. The axle register hole is 3.1" for both. Where I'm going with this is, because my truck is strictly a "grocery getter" ( no hauling/pulling/towing etc.), I'm thinking of pulling the axles from my current rear, taking off the 10" brakes/backing plates, and putting on the 11" duo/servo brakes and new backing plates from the '86 rear onto the '89 housing. Gonna have to check the bolt pattern on the axle housing flange to see if the earlier plates have to be changed. I would imagine they're pretty close to the earlier axle. Also, the earlier axles use a 1/2-20 stud whereas the '89 axle uses 14mm-1.5mm studs, so I'll have to open the drum bolt holes a little for stud clearance. Sound feasible? I'm sure some will say "Why not just swap rear ends?" I could do that but I don't know if the axle pads have the same spacing. Would hate to pull my rear and find the locating holes are off by a couple of inches. It'll be easier for me to just pull off the inspection cover, yank out the C clips and pull the axles. When you get to be my age (76) things aren't as easy as they used to be. It'll be a sad day when I can no longer wrench on my cars. Anyways, let me know what you think. Thanks

 

[Sean Buick 76]

From my limited knowledge on these particular rear ends I agree that swapping the axles and other brake parts is the best bet! I could be wrong however I’ve read that sone 10 bolts are 28 spline and others are 30 or 31 so I think the first thing ti check is that. The other item that could an issue is the width, check both diffs to ensure they are the same width. Is the rear the gear ratio that you want or do you know?

 

[Leeztruk]

I don't intend to change the whole rear end. Just the backing plates and brakes from one to the other. I'm aware of axle spline differences also, so there's no swapping of these. Besides, the stud threads are different as well. That could really be confusing for the next owner. The axle protrusion appears to be the same, one to the other, as the drum depth seems to be the same from the 10" to the 11". Both rears are 3:08, but it doesn't matter as I don't want to swap the whole rear end

 

[Schurkey]

Let us know how this works out. Could be a game-changer for folks "stuck" with 10-bolts.

Let's hope the backing plates will swap from Square-body 10-bolts to GMT400 10-bolts.

Are the Square-body 10-bolts the same 8.5" differential assembly as the GMT400s? I don't remember square-bodies having problems exploding the differentials like the GMT400s.

 

[Caman96]

Let's hope the backing plates will swap from Square-body 10-bolts to GMT400 10-bolts.

According to this, they are different.

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[Leeztruk]

Yeah, this may not work. Pulled a backing plate from the early C10 rear and it appears that the plate is stamped to closely resemble its' mounting flange. From the pictures provided by Caman96, the later flange may be too large to fit within the indention. Also, the tubing holes in the above pictures have no bearing on the center hole of the plate. There is a machined area around the tube that "locates" the plate for the retaining bolts. When it gets warmer, I'll pull my truck's axle apart to see how far off the newer axle flange is, and even if the earlier plate can be modified to fit it.

 

[Schurkey]

Bummer.

 

[Drunkcanuk]

Bummer.

Well said! Lol
Was hoping this would work

 

[RacerM95]

Take a look at this, maybe this is your answer instead ? All parts are relatively easy to get

 

[Caman96]