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.

That definately isn't normal, even if it was cheap parts but a big question is did this start after going off road? It sounds like it was improper installation and I also believe they used the wrong gear fluid. That low of miles the fluid should still look new. I'm interested to hear what you find out though..

Team, reporting back here. The culprit was the thread on one of the third member towers. The load bearing side that also has the locker. The thread was beginning to collapse, which lead the backlash to increase over time since it’s one of the places where it’s controlled on the ring side. Picture here for reference. The installer said they’ve seen this on a number new of the 8.2” diffs with locker - says it’s the weak point.

Labor was covered under warranty. Parts weren’t - Nitro does not honor its warranty. Nitro basically said they don’t cover the gear noise and blamed it on the driver. The installer said this kind of customer service is very common for Nitro (beware). So I went with Yukon for new gears. The installer also put some tig welds with my consent to make sure that side does not come off the thread.

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I'm a bit confused on what it means that the thread was collapsing. The threaded adjustment nut (the big ring you use a spanner wrench to tighten) was collapsing internally or the threads cut into the cast steel housing were failing? I've built a few of these diffs. I haven't seen it myself, but it seems a bit unusual. The bearing caps should hold the outer carrier bearing race in place once the preload is set even without the threaded adjuster nut. Ideally the bearing caps slightly compress the adjuster nut and mostly clamp down on the bearing race to hold it all tight.

But the bearings do wear. And if they were not fully seated when installed or they had more than normal wear I could see a loose ring carrier. Often 100K+ mile Toyota diffs will have close to zero preload. The best advice I know of from a very experienced pro builder is to basically tighten the toyota carrier bearings as tight as possible including any used ones you pull out. Just crank them down really tight to maybe 100 ft lbs or more on the adjuster spanner wrench. More than you can do with one of those scissor looking spanners.

Glad you got it sorted out! Hope it stays put from now on.

Also FWIW - at least as recently as maybe 3 years ago it was the case that there is only one source for 8.2 gears, so it doesn't matter who's logo was on the box. They're all from Circle K (Samyong). Nitro just charges more for the same thing as Yukon or Precision or anyone else.

Thanks, I’ve rebuilt these diffs too, albeit without the locker, and I was equally puzzled. The shop said there’s too much load on that side so when they removed the threaded ring there was very little thread left on the carrier. My guess is the clip wore out and developed play? Let’s see if the welds help keep it in place. The shop owner said they’re considering calling every 4runner they did the gears for to also put a few welds to prevent this issue as they’ve seen it before too. And the shop said the same thing about Nitro and Yukon - made in the same factory but Yukon has good customer service while Nitro never honored their warranty.