Diff 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 .009 to .010. 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??

Thatdude596 · Dec 10, 2015

there was recall on the rear pinion nut but doubt that helps ya...clueless on rear ends unless they big and round lol

CVX20 · Dec 10, 2015

MarkV said:
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??

IF THAT'S NOT A MISPRINT THEN YOUR BACKLASH IS TOO TIGHT.
I don't know what the exact spec is on your particular diff,but a general rule of thumb is .007 to .009"(that's 7 thousands to 9 thousands of an inch).You have one thousands of an inch clearance if you set it to those specs.

BTW If you used the original gears they could already have a noise built into them by running it with a loose pinion nut.If it already is worn enough to make a noise no amount of adjusting will get rid of it.The only way is to replace the crown and pinion.

Rustycowl69 · Dec 10, 2015

did you take a picture of the pattern, drive and coast side? Did you load the diff with a pry bar when you checked the pattern. did you use case spreader, so you preloaded the diff bearings with proper shims?

MarkV · Dec 10, 2015

CVX20 said:
IF THAT'S NOT A MISPRINT THEN YOUR BACKLASH IS TOO TIGHT.
I don't know what the exact spec is on your particular diff,but a general rule of thumb is .007 to .009"(that's 7 thousands to 9 thousands of an inch).You have one thousands of an inch clearance if you set it to those specs.

BTW If you used the original gears they could already have a noise built into them by running it with a loose pinion nut.If it already is worn enough to make a noise no amount of adjusting will get rid of it.The only way is to replace the crown and pinion.

Sorry miss print....Thanks for picking it up!!

I see. So how much more do i try to get it right or should i give up on it and run it?? I could take my other axle apart and use those gears? It is tight and clean.

MarkV · Dec 10, 2015

Rustycowl69 said:
did you take a picture of the pattern, drive and coast side? Did you load the diff with a pry bar when you checked the pattern. did you use case spreader, so you preloaded the diff bearings with proper shims?

What side do you load with a pry bar? Left or right? I have come across using the parking brake or just holding the pinion with you hand to put resistance on it.

This axle had threaded cups for the preload.

CVX20 · Dec 11, 2015

Well being as it has the adjusters it might be worth playing with a bit.A lot easier than shimming.I can't tell from the pictures what your pattern is right now.The thing is even if you have a bit of an annoying whine after it's all set-up properly it's not like it's going to blow apart.It could run with the whine forever.

MarkV · Dec 11, 2015

I will play with it some more. Yea it was kinda hard to get a decent pic of the marking.... it was not marking very obvious. Thanks

CVX20 · Dec 12, 2015

You really need a fair bit of drag on the crown while turning the pinion to get a good read.You don't need to paint it on too thick either,just cover the teeth.

MarkV · Dec 12, 2015

I have read and heard that you turn the crown and drag the pinion. And i have read that you turn the pinion and hold the crown. So i will go with what you said. Ok, I think i might have been putting it on to thick. Thanks for the help!!

CVX20 · Dec 12, 2015

MarkV said:
I have read and heard that you turn the crown and drag the pinion. And i have read that you turn the pinion and hold the crown. So i will go with what you said. Ok, I think i might have been putting it on to thick. Thanks for the help!!

The pinion drives the crown.Makes more sense to do it that way.

MarkV · Dec 12, 2015

CVX20 said:
The pinion drives the crown. Makes more sense to do it that way.

That is what i kinda thought. I will be marking in a bit..... Will post a pic

MarkV · Dec 12, 2015

Here is what i have so far....

MarkV · Dec 12, 2015

Here is a video of the diff running.

MarkV · Jan 5, 2016

So i ended up putting used gears from my spare axle in my diff. It runs like new first setup....well first try for those gears. It had .012 backlash before i took the used axle apart so i put it at .009 backlash in the truck.

Skillz · Feb 23, 2017

Hey I am having a noise 2 it goes away when I let off the pedal and comes back under load...I took the cover off there are lots of metal particles in the oil and one of the teeth on the ring gear is chipped but otherwise looks ok....took the drive shaft off and the pinion nut is tight and it has no play up down or sideas to side...what so u guys think

smiley · Feb 25, 2017

MarkV said:
So i ended up putting used gears from my spare axle in my diff. It runs like new first setup....well first try for those gears. It had .012 backlash before i took the used axle apart so i put it at .009 backlash in the truck.

So the gears were indeed wore out I assume? I have the same issue with mine and caused by the nut being torqued correctly after the recall. So then had to do the pinion bearings and my mechanic said he could not get the whine out and only way to do so would be to replace. Which I probably will do soon.

MarkV · Feb 25, 2017

smiley3303 said:
So the gears were indeed wore out I assume? I have the same issue with mine and caused by the nut being torqued correctly after the recall. So then had to do the pinion bearings and my mechanic said he could not get the whine out and only way to do so would be to replace. Which I probably will do soon.

The whine was the gears. Miss worn from the lose pinion nut. The gears look visibly ok. Swapped them out and problem gone. I just put in used gears.

MarkV · Feb 25, 2017

Skillz said:
Hey I am having a noise 2 it goes away when I let off the pedal and comes back under load...I took the cover off there are lots of metal particles in the oil and one of the teeth on the ring gear is chipped but otherwise looks ok....took the drive shaft off and the pinion nut is tight and it has no play up down or sideas to side...what so u guys think

Do you have a limited slip diff? They are know for making metal particles out of the carrier. The is little clips that brake and slide out a bit and wear a grove in the diff case. Also the clips come out and can mess up your gears.

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