Rear end noise - related to pinion nut tightness?

[Blakers]

My truck has a whine in the rear end while under load and while the engine holds back. Almost no load at a coast. Oil looks good and no unusual wear.

Could the noise be related to the tightness of the nut on the pinion flange?

About three years ago I removed the pinion flange to replace the seal. Before I took the nut off, I marked it, but I was never able to fully tighten it as much as it was before. Maybe 10 degrees on the turn of the nut shy of what it was.

I'm wondering if that little bit of difference would be enough to allow the pinion gear to change alignment under load to cause the noise? From my recollection, the noise did not start immediately after changing the seal, but not long after that.

It's my 03. 322,000 miles. Thanks!

 

[Darkbloodmon]

About three years ago I removed the pinion flange to replace the seal. Before I took the nut off, I marked it, but I was never able to fully tighten it as much as it was before. Maybe 10 degrees on the turn of the nut shy of what it was.

I would say yes, I replaced my front pinion seal following the 03 FSM procedure of measuring the rotating torque, then tightening the nut x amount more than the recorded torque. It's not like a drive shaft and putting it back where it is, the thousandths of play do make a difference.

Here is the tightening excerpt from an 03 FSM for the rear 11.5 AAM.

"Measure pinion rotating torque with an inch pound torque wrench and compare it to recorded measurement. Tighten pinion nut in small increments, until pinion rotating torque is 0.40-0.57 N·m (3-5 in. lbs.) greater than recorded measurement. (8) Rotate pinion several times then verify pinion rotating torque again"

Have you checked everything else that could be making a noise under load in the rear? Tires, rear axle bearings?

 

[Blakers]

I would say yes, I replaced my front pinion seal following the 03 FSM procedure of measuring the rotating torque, then tightening the nut x amount more than the recorded torque. It's not like a drive shaft and putting it back where it is, the thousandths of play do make a difference.

Here is the tightening excerpt from an 03 FSM for the rear 11.5 AAM.

"Measure pinion rotating torque with an inch pound torque wrench and compare it to recorded measurement. Tighten pinion nut in small increments, until pinion rotating torque is 0.40-0.57 N·m (3-5 in. lbs.) greater than recorded measurement. (8) Rotate pinion several times then verify pinion rotating torque again"

Have you checked everything else that could be making a noise under load in the rear? Tires, rear axle bearings?

Thanks for the reply.

Yes, in the months after the seal replacement I did have tire issues, and I did have a rear wheel bearing go. But after replacing both wheel bearings, and now knowing my tires are good, I am certain it's the rear end. The change in tone from positive load, to coast, to negative load is a telltale sign to me.

The tire and bearing issue did add to my frustration though. I also rebuilt the transfer case this spring with new bearings, chain, and sprockets. It was in remarkable condition except for the chain, which had been jumping under a load.

 

[Darkbloodmon]

Thanks for the reply.

Yes, in the months after the seal replacement I did have tire issues, and I did have a rear wheel bearing go. But after replacing both wheel bearings, and now knowing my tires are good, I am certain it's the rear end. The change in tone from positive load, to coast, to negative load is a telltale sign to me.

The tire and bearing issue did add to my frustration though. I also rebuilt the transfer case this spring with new bearings, chain, and sprockets. It was in remarkable condition except for the chain, which had been jumping under a load.

No problem, I was waiting for things to finish cooking, hope you had a nice Thanksgiving.

I'd take a measurement of my rear end to give you something to go off off since It still has an OEM pinion seal but with bearings and shims its pretty truck specific when its first assembled from my understanding.

 

[Blakers]

Thanks! It's not super critical right now since I only drive 30 miles round trip to work, but when I get some time on a nice day I'll borrow a 3/4 inch impact from someone, pull the drive shaft off and see if I can feel any end to end or side to side movement. Then just snug it up a tiny bit with the impact and see if it makes a difference. I'm not going to go crazy on it, and I'll make sure the pinion turns freely. If this works it will be a simple repair I should have done two years ago. If not, then I guess I have to either tear into it or find someone who wants to do it.

 

[Darkbloodmon]

Thanks! It's not super critical right now since I only drive 30 miles round trip to work, but when I get some time on a nice day I'll borrow a 3/4 inch impact from someone, pull the drive shaft off and see if I can feel any end to end or side to side movement. Then just snug it up a tiny bit with the impact and see if it makes a difference. I'm not going to go crazy on it, and I'll make sure the pinion turns freely. If this works it will be a simple repair I should have done two years ago. If not, then I guess I have to either tear into it or find someone who wants to do it.

Small increments with repeated measurements are the name of the game, if you do have to tear into it it shouldn't be terrible in compared to the front end.

You could try calling a drive train/4x4 shop and see if they do in housing adjustments, I know the 9.25 AAM can be.

 

[sag2]

If the pinion was loose it more than likely is damaged the ring and pinion and tightening might make the noise change but probably not go away. Unless it gets really bad just drive it till it needs a complete rebuild.

 

[Joseph Donnelly]

When changing the seal on these diffs, the nut definitely should go back on the full amount it came off to get the proper preload and bearing clearance. If it doesn't want to do so, rotate the pinion some to help the bearings re-seat fully, and continue tightening.

 

[Ozymandias]

I never tried to do that job on the RAM without an impact - I did on the Jeep but there is less torque needed and even there it was a pita to say so.
Get a impact and bring it right back to were it was.
Should solve your problem if it isn't to late to do so.

 

[Blakers]

I never tried to do that job on the RAM without an impact - I did on the Jeep but there is less torque needed and even there it was a pita to say so.
Get a impact and bring it right back to were it was.
Should solve your problem if it isn't to late to do so.

Thanks. My 1/2" Ingersol Rand impact would not do it. I should have borrowed a 3/4" impact at the time. There could be some damage, but nothing really noticeable when looking at the ring gear. And no grindings in on the magnet. The loads my truck handles are so meager compared to what it could do. For the most part it takes me to work and back, and a light trailer a few times a year.

 

[Blakers]

A friend does have a center section of a rear end that I may grab just in case. It's low mileage from a later 3rd generation truck. Supposed to be the same ratio - 3.73. I guess the whole axle was replaced under warranty for some other issue. Not sure of details yet.