I would suggest that you buy an entire axle assembly from the junkyard. If he sold you the whole guts out of one for $80, the whole thing would run around $100 I am guessing.
I used brake cleaner and some rags to clean it up inside and got a good look at the ring/pinion/spider gears.
You will need to buy a few cans of brake clean, 4 new U-bolts(do not re-use these), new diff lube, a tube of RTV sealant, 2 new axle seals and a new cross pin bolt. (the tiny little bolt that holds the cross pin in, these are notorious for breaking)
I strongly recommend removing the axles and checking the axle bearings, replace if needed, check the surface of the axle where the bearing rides. If you can feel anything with your fingernail, replace that axle from one (from the same side) in your other rear end (assuming that it is in good shape, of course).
Also, take out the fill plug before going much further as it wont help you to hang this under your truck unless you can fill it.
This is the easiest time to replace the axle seals as they are not expensive and, god only knows when the ones in there now are gonna start leaking. I always add just a touch of grease on the axle bearings and the back side of the seals.
If the backing plate is bent on the one from the junkyard, take it off and replace it with the one on the other rear end. Replace both of the U-joints on your rear driveshaft (if you have not done so already). The rest of the job is a straight up remove/replace.
From start to finish would run you about 5-6 hours, but if you can get some help it will go faster.
Good luck
: anyhow if i ever have to do it again ill change the rear end as a whole.
