I have a 2001 XLT 4x4 manual trans with about 200k miles. Long story short about a year and a half ago I took my truck to a mechanic to get the pinion seals replaced on front and rear diff, and I'm worried the mechanic didn't set the preload on pinion nut back correctly for good reasons-
1- Friends let me know afterwards (of course) that particular mechanic was not known for good quality repairs with cutting corners and not taking responsibility for failed parts they installed.
2- After knowing this, I of course went through and inspected diff, driveshaft area. My diff was hot. I removed the fill plug and there was no oil, just a small puddle sitting at the bottom. The gears were hissing they were so hot from lack of lubrication and heat dissipation. I topped off the front and rear diff with NAPA 80W-90 gear oil and that was that.
Now fast forward almost 2 years later (I may be way too concerned for nothing), but I am pretty oblivious to how the drivetrain parts are supposed to behave, and my truck isn't just a drive to the store and back truck, it's something I could be driving a thousand miles plus on a single trip so I need it staying reliable and address all necessary issues. It's been nagging at me for some time, especially after inspecting my front and rear differential fluid a few days ago. So, it's been about 2 years and probably 8-12k miles since I put the new fluid in the diffs. My front diff fluid was very healthy looking, a clear-golden color like the day I put it in. Now the rear diff was dark, almost black. Not gritty feeling but definitely very dark. Plus, the magnet was holding a good amount of grey mush, luckily no chunks. It just makes me wonder if the diff is running too hot which is damaging the fluid and if it's trying to go on its way out. A heat gun would come in handy, but after driving I can hold my hand on the diff cover for about 2-3 seconds until it starts to hurt. If it is normal than I am sorry for wasting your time to those that got to the end of this!
I also threw a video together wondering if the play from driveshaft going into differentials is a normal amount. Looking to settle my insecurities now and forever (until next problem hits)
https://youtube.com/shorts/9jkjoPQJPYo?feature=share

 

I personally did that work myself. True about the preload. He needed a new nut. Preload is set with tires and drums off. Technically, a crush sleeve is a one time thing too, but i reused it on mine. Running without oil is bad.

If you were mech inclined, i’d pull the cover and have a look.

 

On that video, you can’t go by that because the carrier is turning, the side gears have their slack, the axle splines have their slack.

You take the cover off , have somebody hold the drive shaft or rig up something to hold it. Then rock the carrier by the ring gear. That is your backlash. Shouldn’t be much. You need a dial indicator to read it.
Specs are on the internet.

 

Rear differential housing plate should run 130-150degF, and up to 200degF if carrying or pulling a heavier load
Over 200degF would be the sign of a problem

Same for front differential if its being used

130degF is way too hot to hold your hand on for more than a few seconds

Yes, get an IR temp reader

 

8.8 Diff rebuild List :

ring & pinion
pinion bearings, 1 xtra to wallow out for shim / tooth pattern testing
2 crush sleeves - Update : i will go with the eliminator kit.
pinion shims
carrier bearings
carrier shims
pinion seal
pinion nut
dial indicator with mounting options
a press, with various blocks, under bearing jig
spiders, side gears, crosspin all depends on condition.

How much would all this cost ?

 

Well, they used the old nut so rip to my bearings sometime I guess. I also highly doubt they took the time to take the tires and drums off. Probably used the same crush sleeve too since it's possible to do so. They're the type of guys to tighten until it feels good enough to call it good.

 

Well, they used the old nut so rip to my bearings sometime I guess. I also highly doubt they took the time to take the tires and drums off. Probably used the same crush sleeve too since it's possible to do so. They're the type of guys to tighten until it feels good enough to call it good.

 

Alright, so sounds like overheating isn't a problem with mine, I think. I could hold my hand on for 3-5 seconds if I wanted to so that's a good sign.