9.5 rear diff/drum brake question

[682XLR8]

Good Morning-I've spent hours reading thread after thread on the 9.5 differential swap for my 1992 C1500 and have a pretty good idea what's involved, but I have a question.
I found online a 9.5 rear diff in a wrecking yard about an hour from here, diff is in a '97 C2500, six lug SF, so after taking a few measurements on the 10 bolt currently in my truck, I took a cruise over to the yard to check it out. Measured the leaf spring perches, they came in at 47", same as my truck. Measured between the brake backing plates, and the 9.5 came in about 4" narrower, so at this point, I stopped and decided some more research was in order. After I returned home I got to thinking, the rear brakes on the C2500 (11"?) seemed to be larger than the ones on my C1500, could they be wider also? The truck still had the wheels on it and fit the wheel wells ok, so I'm thinking if the brake assembly was wider, that would make up the difference, but I can't seem to find any definitive info on the subject. Someone please steer me in the right direction, this rear is complete, drum brakes, u-bolt brackets, and surprisingly little rust (I'm in Michigan) and hate to pass it up if it will work in my truck
Thanks in advance!!

 

[GoToGuy]

Think about it for second. The spring perch is the same distance. The drums are fricking huge. You've seen other 2500s driving around right? Are they some mutant conversion? Did you measure from the lug axle face , most outer dimension for total width? Is the one your looking at same lug bolt numbers as your original truck? 5 or 6 ?
Brake shoe size is on the last page of chapter 5 Brakes, specifications, by RPO , JB5 , JB7 , etc...

 

[DerekTheGreat]

I'm also on the hunt for a CLEAN housing. I'm surprised at how many are rotten around the U-bolt bracket area and whatnot...

Anyway, the spring perches are the same width (47"), 4WD vs 2WD. It's the overall width that varies, 65" for a 2WD housing and 68" for a 4WD. The brakes are much larger and better on the 9.5" axle.

You will need to either swap the yoke off your 8.5 to the 9.5 axle or buy the special U-joint.

 

[GoToGuy]

Part of the problem is the bottom u bolt flange, needs a hole or bigger hole so it drains, and the crap doesn't sit in it and start a corrosion runaway .

 

[682XLR8]

Think about it for second. The spring perch is the same distance. The drums are fricking huge. You've seen other 2500s driving around right? Are they some mutant conversion? Did you measure from the lug axle face , most outer dimension for total width? Is the one your looking at same lug bolt numbers as your original truck? 5 or 6 ?
Brake shoe size is on the last page of chapter 5 Brakes, specifications, by RPO , JB5 , JB7 , etc...

Makes sense to me, just want to be sure before I drive another hour to finish measuring or buy a part that won't work. I mentioned in my post that I stopped measuring when I saw the difference in widths, I didn't get to measuring the outer hubs/overall width but 65" is what I have on my truck and what I'll be looking for on the 9.5.
You're right about the drums, they are friggin' huge, hope my wheels fit as I have aftermarket aluminum wheels

 

[someotherguy]

Yeah the measurement you're looking for is WMS (wheel mounting surface) to WMS, not backing plate to backing plate. That is, assuming the drums are still there. If not, then of course the axle flange is the next closest thing.

Richard

 

[Stormbringer]

The six bolt drums are much deeper than the five bolt. When I did this I had to re drill the six bolt drums to the five bolt pattern. I used square body five bolt 15x8 rims and they fit fine.

 

[someotherguy]

The six bolt drums are much deeper than the five bolt. When I did this I had to re drill the six bolt drums to the five bolt pattern. I used square body five bolt 15x8 rims and they fit fine.

I had my C2500LD re-drilled for 5 lug as well, axles and drums. So here's a formerly 6-lug 9.5" 14 SF, with a 20x10 wheel with 6" backspacing. Fits great. Not weirdly narrow or anything. This is essentially the same fitment you'd see on a regular 8.5" 10 bolt.

You must be registered for see images attach

Richard

 

[682XLR8]

I went back to the wrecking yard yesterday and measured the axle width with the drums on, 65" right on the dot. The rear was removed from the vehicle and cover removed to check the gears. Everything looked great, so I bought the rear end, brakes and U-bolt mount plates, brought it home and immediately started tearing into it. Brakes and drums look good though a little rusty. Removed the axles, bearing surfaces all look good.
The plan at this point is to remove the carrier and pinion and have the housing bead blasted, have the axles and drums redrilled for 5 lug, and install a limited slip unit

 

[someotherguy]

Since you're in a rust area, pay close attention to the axle tubes where the U-bolts made contact. A couple of people have found pinhole rust there that created a leak. They can certainly be repaired, just something to be aware of.

Richard