I've been trying to trace vibration at highway speeds (60-72mph worst).
I've had new tires and alignment (needed new tires anyway) and that
didn't help. I just changed the rear driveshaft u-joints, and unfortunately
they were in great shape. Still greasy inside and needle bearings intact.
PIA but I learned a lot. I raised the rear vehicle and noticed play on driver
side rear wheel. Both up an down and side to side play. I'm going thru that
service manual to try to figure out what needs changing here. I did front
suspension this summer (hub assemblies, upper control arms, balljoints).
Not sure what the rear entails, any suggestions appreciated.
130K miles Dodge Ram 1500 4x4 quad cab SLT 5.7.

 

in/out is normal, but up/down and side-side is a sign of a worn/bad axle bearing. You thought the u-joints were a PIA, wait till you hear this...lol... While the axle bearings themselves aren't expensive, they are a PIA to change. Here's what you need to do, and I highly reccomend doing both at the same time.
1.Take off the rear differential cover and let the fluid drain.
2.rotate the carrier until you have access to the retaining pin bolt. Unbolt it and remove it. This allows the axles to be pushed inwards so you can remove those c-clips.
3.Take off your wheels
4.Unbolt and hang your calipers(don't open the lines) and pull off your rotors(you'll need to unhook your e-brake cable)
5.With your brake assembly off, your going to push in your axle assembly. It will only move 1/8" or so. Now, with them pushed in, your going to need to go into the carrier housing and use either a magnet(never had good luck with one) or a long screw driver and push the c-clips off the axles. Be careful not to get them caught up in the gears when fishing them out after knocking them off of the axles.
6.Once the c-clips are out, you can now slide out the axles. Pull the straight out and don't bang them around. There are splines on the very far end that you can damage.
7. Pry the seal off
8.Take a not on how far the bearings are pressed into the housing. Measure the lip depth if you need to. I would also look at the depth on the seal too.
9. Remove the bearing with a puller(Advance Auto and Autozone rent these tools for free with a deposit)
10. Install new bearings and new seals.
11. Use emery paper or scotchbrite and scuff up the race pf the axle. This is the area where the seal and bearing contact. You'll want to get the rust off the seal line but don't go so crazy your removing lots of metal.
12. When you re-install the axles, be very cautious not to use the bearing and/or seal as a resting device so you can slide the axle in. You need to do your best not to rub the axle on those because you can burn the seal, and score the bearing surfaces of the needles.
13. Pay attention to where the seal falls on the axle tube. If the seal is rubbing further out and on the rusted area, your going to want to pull the axle back off and sand some more. It will leak if it's not done correctly.
14. Put the clips back in, pin back in, and seal up the diff with RTV sealant. I use Permatex 1-minute RTV. It sets up in no time so you can pour diff fluid in and drive right away, no need for the sealant to dry like the normal stuff.
You'll use 2qts 75w-140 Synthetic plus a bottle of friction modifier(LSD only) or 2.25qts of 75w-140 if open diff.

Your looking at a $100bill for parts including new fluid and roughly 5+hours labor for a beginner.

 

Dang! Another big project. And I just changed the Diff fluid with RP.
thx for the writeup dirtydog.
So apart from the fluid what am I changing. Axle bearings, seals and RTV/gaskets?

 

^^ Yes. 2-Axle bearings, 2-seals and a tube of RTV sealant for the diff cover. That'll do both sides. You'll need emery cloth/paper or scotchbrite for the axle tube sanding. As for the fluid, you could catch all that RP in a clean pan and re-use if you'd like.