About 1.5 years ago, had a shop put nitro 4.88s into my 4R on 33s. Followed break in instructions from the shop and changed the gear fluid as required. Generally change gear fluid every 15k miles. Truck sees trails every month or so but rarely difficult trails.

About a month ago, started noticeable considerable gear whine coming from the rear only when hitting the accelerator. Tested the back lash by wiggling the drive shaft and appears to be lots of play / sloppy backlash. Drained the oil, and the oil was clean but the magnet on the drain plug had lots of caked sludge (too much considering fluid changed in July) as well as small sharp bits stuck to the drain plug magnet. All in all, the truck probably has about 30k miles on the new gears and the whine is now loud enough that you have to talk louder when driving.

Do you guys think the gears were installed improperly or this is normal wear and tear?

Thanks!

Improper installation. I Have over 250k miles on my Nitro gears and they are as quiet as stock

Mine too

not normal

My last gear install I pulled out after only maybe 100 miles and found that they had terrible gear pattern and had failed to crush the sleeve fully leaving it with no preload on the pinion bearings. If you have a lot of backlash (hard to measure correctly without pulling the diff) there's a good chance they screwed up the pinion crush sleeve and it has now compressed more and become loose.

Toyota rear diff gears are extremely easy to setup. Probably the easiest differential that exists to setup. If someone didn't get perfect backlash on them - they have no business working on diffs.

See if you have any play in the bearings on the pinion. Possibly pull the drive shaft and see if the pinion nut is properly staked and/or if it has moved at all.

Thanks all. The shop agreed to take a look at it, so will report back once I Know.