I have 98 4wd xlt f-150. I've replaced the passenger side rear axle shaft, seal and bearing 2 times now. It's about a 3 year rotation between replacing it and it wearing out again. I can only think that maybe the housing is bent possibly. I replaced the engine 2 years ago with a crate engine and would like to make the rear-end more reliable. I thought about going to get one from a junk yard but what would you guys suggest? It's not a bad job, i'm quite good at doing the repair now!

EDIT: I think it has been replaced 3 times now!

 

I guess what I'm asking is does anyone have experience with parts from junkyards. Is it more often you get a lemon than not? I think I can get a rear end for 200 at the local yard and the parts to fix the existing rear end will cost maybe a little more. Which if I get the junkyard one, I'd drain the fluid and look at it and refill so that'd be about 40 bucks added to it.

 

Some salvage yards either know the rear to be good or will provide some kind of warranty if found with a problem.
The cost to replace some/all parts in a possibly troubled differential will cost more to get the tools to set them up or have someone else do it than just exchanging it for another.
Usually , before installing a used differential, we drain and check for metal particles/.shavings in the carrier assy. If all is OK , just replace with new correct lube and install as usual.

 

I have a all the tools to do the job with already. I usually start hearing a noise and i'll jack my truck up to wiggle that rear passenger tire and I'll feel a little slack, so I know it's wearing a groove into the axle shaft. It's been the same every time. I tried changing the bearing and seal early also. Always the same result about 3 years 60,000 miles ish and it starts leaking fluid. If I get a used rear end would you break it down and check the bearing, seals and shafts before installing?
My rear end is a 8.8 with3.55s Limited Slip

 

We may be talking about 2 different things .
When I stated the tools to set up ,I am referring to a dial indicator, shims etc. If you take any specially set up parts apart you need to have the knowledge and tools to set up the tolerances and gear pattern etc.
Usually if you remove the housing cover , you can get a pretty good idea of the condition of the rear just looking at the lube and absence of metal particles.
Depending on what you see should help determine if you want to get involved with replacing any seals etc.

 

Yes, I was talking about the tools to change the seal and bearing. I haven't been able to find an exact replacement. I have found the 8.8 with 3.55s but not limited slip. That rear end is a few hrs drive. Locally,I I have found some 8.8 rear ends but with different gear ratios. The local one seems to be in good shape. Can you make a non limited slip into a limited slip? I'm guessing I could take the parts out of my old one and put it in the new one. I would need the tools you were talking about. I have no experience with doing that job but if I can find good directions i'm sure I could handle it.

EDIT::

I watched a video... a few actually of people taking apart the rear axles. I don't think I want to have to change the pinion gear. If I took the old limited slip diff. out of my existing axle and took the open out of the new axle. As long as I used the same clamps and shims from the new axle and put them all back in the correct spots would I still need the dial indicators? I'm thinking now that because the LSD had the clutches that the shim size will have to be changed. I may have to get a shop to do that part!

 

For what it is worth,
There are times when we alter things and nothing bad happens and sometimes we get lucky and get by.
As my good ole uncle Murphy once said , "I'll be there watching" and he was and he did and I paid."
Once you alter anything in a differential even replacing only the carrier bearings ,tolerances change and Murphy gets in there , so my suggestion would be to have someone experienced with setting up differentials and has the right tools, do the job for you and let Murphy go work someplace else. lol.
Hope you rec'd my point. .

 

Yea, I know what you mean! I think I'll just pay someone to do that part of it.

Thanks!