I have a 3.55 8.8 drum brake rear end that i need to replace.
Is there any difference between the drum and the disc(other than the brakes) that would have to be changed to allow swapping to a disc rear end?
It looks like the parking brake cables attached the same way to the chassis.
What is different about the 9.75 (other than the ring gear size) and will it interchange with the 8.8.
The local salvage yard has a 3.55 9.75 rear out of a 1998 F150 in stock ,but it did not know if it would bolt up the same way or if anything would have to be changed.
Does anyone know of a good interchange reference for the F150's through the years?

 

Does your 98 have ABS? if so and it probably does, that will complicate things a little more.

 

I think it does have abs on the rear only,but wouldn't that be fairly standard on the F150's?
The salvage yard has a 1998 9.75 that came up on a vin number search as an interchange option.

 

I think the driveshaft lengths may be different between the 8.8 and 9.75.

Why do you need to replace the rear? I'd fix it rather than taking a chance on a junkyard rear.

 

I was in an accident in April and the rear end is bent.
Unfortunately rebuilding my rear end is not an option.

 

One tedious potential way to see what is different is to compare part numbers. If a VIN# is needed see if you can use another truck's vin to look up the parts.

War story warning! I bought a used 79 V8 Mustang years ago and the rear brakes locked up prematurely. I pulled out my car magazines and read about the test of the 79 V8 Mustang and one comment all the editors had was that the rear brakes locked up prematurely. Just so happened that I read an article in the newspaper about the NHTSA trying to get Ford to recall them to fix the problem. Ford refused to recall the cars but promised to fix any customers car who came in to their shop with the problem. I confirmed this with a phone call to the NHTSA. Both of the local dealers in Raleigh denied any knowledge of this. One dealer claimed they called "Ford engineering" and they didn't know anything about the issue. So, finally I went to the parts counter and we compared part numbers for the entire brake system between the 79 and 80 V8 Mustangs because the issue had been fixed in the 80 model. The only part number that was different was the proportioning valve. So, I bought a 1980 proportion valve and installed it and that fixed the problem. Their was a tube fitting that was different on the 80 valve I presume to prevent the 79 valve from being used after Ford realized their mistake. This is one of two safety recalls that Ford refused to make on vehicles that I have owned. The other is the cable that holds the spare tire on my 2002 truck. It will break and drop the spare tire. The replacement cable has a spring on the end of it that reduces the stress on the cable. My spare tire dropped somewhere and I was unaware that it had dropped. I just hope that no one behind me ran over it and wrecked.