Diff Setup / Noise Questions

MarkV · Dec 10, 2015

So my pinion nut had come off a while back. And so while it was in the garage i did a engine job. Long story. But i fixed the notorious tick it had. So now i move on the the second job.

The rear diff. A Chrysler 9.25. I have put all new bearings in it. Also i have put a Detroit TruTrack in. I assembled it according to the repair manual. And it all went together quite well. I took it for a ride. And i noticed a noise when i applied power. Not when coasting. I don't think when i floor it. Just coasting to power. It sounds like misaligned gears. Kinda hard to explain the sound. It will make the noise when i put it up on blocks and run the tires at 80-90km (50 mph)

Backlash is at .0009 to .0010. When i mark the gears it shows a good pattern. The adjuster cups are at 75 ftlbs.

I have another axle i bought and is in decent shape. I could swap gears out.....

Any one have any ideas??

knucklebuster27 · Jan 5, 2016

Pinion nut came off? If it was loose for an extended period of time it could have engraved a wear pattern in the gears and now you are out of that wear pattern back in the original wear pattern that has been modified by the loose pinion nut wear pattern. Clear as mud. Lol. Without looking at the gears myself I would say you are on the correct track with it being the gears that are making the noise. When I service a rear end I always check backlash first, before disassembly and put the back lash back to what it was when going back together if it is at least close to spec. and using the same gears just to help avoid noise. If you could pull a wear pattern on the other gear set and match it up when installing it in your rear end that would be ideal but not very plausible. I would just check back lash in other gearset, swap gears and hope it's not noisy. Good luck

MarkV · Jan 5, 2016

I swapped the gears. The other axle backlash was .012 so i put it in at .009 backlash. It runs just fine know!! I did not think that it would wear a bad pattern on them that fast but then i dont know how long the nut was loose for....

GoldDot · Jan 5, 2016

There is a tsb for this axel that basically has complete install instructions with pictures. Safety recall n08.

According to that backlash spec is .005-.008" and requires adjustment if outside of that range.

CVX20 · Jan 6, 2016

MarkV said:
I swapped the gears. The other axle backlash was .012 so i put it in at .009 backlash. It runs just fine know!! I did not think that it would wear a bad pattern on them that fast but then i dont know how long the nut was loose for....

Because the pinion was flopping around all the time the nut was loose I'll guarantee that you'll never get the noise out of that set.And like was mentioned if you use a used set then they would have to be set exactly the same as they were when they came out of the donor diff.The only sure way to get the noise out is a new crown and pinion properly set-up.The good thing is that the rearend could last the life of the truck with just that annoying noise.

I would say though that your backlash is too loose now.

Diff Setup / Noise Questions

MarkV

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knucklebuster27

Junior Member

MarkV

Senior Member

GoldDot

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CVX20

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