Opinion needed from pro differential guys

[Qjoh5510]

I had my JLUR regeard a little while ago to 4.88. Since then I’ve been having a whine on deceleration. It’s not super loud but it’s there. After the first break in and about 800 miles of driving afterwards I brought it back and a brand new set of gears and bearings were put in. The problem still exists but has slightly changed in tone and is a little more prevalent now. They claimed everything was meticulously installed to specs. After the gearset was changed out the shop said there was unusual wear on the carrier bearing races of the first set of 4.88s. I’ll attach some photos. Are these wear patterns saying anything to you?

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[DOOKEY]

What brand of bearing are we looking at here?

 

[Upsidwn]

Same thing I was going to ask @DOOKEY

How are they measuring the rotational tq for the pinion preload, and what specs are they going off of?
I’ve talked to a many shops whom “put it to spec” and you find out it’s the “spec they always use for Dana 44s”, and not what that specific diff calls for

 

[Qjoh5510]

What brand of bearing are we looking at here?

Gear set is revolution and they said they use dana spicer bearings.

Same thing I was going to ask @DOOKEY

How are they measuring the rotational tq for the pinion preload, and what specs are they going off of?
I’ve talked to a many shops whom “put it to spec” and you find out it’s the “spec they always use for Dana 44s”, and not what that specific diff calls for

The specs they’re using are the ones listed on revolutions website. I’m also guessing they had a spec sheet in the box the gears came with. The revolution regional rep was there the whole time the second gear set and bearings were being installed to make sure everything was installed to spec.

 

[Qjoh5510]

Let me see if I can find the specs real quick

 

[Qjoh5510]

I can only assume these are the specs they used. It appears that the factory spec for the m220 pinion preload is 12-20 inch lbs and revolutions is 14-19 inch lbs for the D44. Assuming they followed those, it should be within spec.
https://www.revolutiongear.com/installation_specifications

 

[conFUcius]

Paging @chevymitchell though he’s wheeling out west and may be delayed in responding.

 

[DOOKEY]

Gear set is revolution and they said they use dana spicer bearings.

Any chance you have pics of the bearing? Did you see it? Are the same score markings on the bearings?

 

[Qjoh5510]

Any chance you have pics of the bearing? Did you see it? Are the same score markings on the bearings?

I did not get a picture of the bearing and was not there at the time they pulled everything so I didn’t get to see the bearing either. They took all the bearings and gears from the first set back to the R&D team for inspection.

 

[DOOKEY]

I did not get a picture of the bearing and was not there at the time they pulled everything so I didn’t get to see the bearing either. They took all the bearings and gears from the first set back to the R&D team for inspection.

You're going to have a difficult time getting an educated guess with just one piece to the puzzle. In a perfect world... you'd look at all pieces of the puzzle. Which sounds like that's what they are doing.

If you could see the gear pattern after the "failure" and look at the remaining bearings you can start to understand what's going on. Without it... really tough to say what the issue is.

Will you report back with their findings?

 

[stickling9]

we call this 'galling' which occurs under high sliding load. Your bearings are not turning, which may be from too high preload? Hard to tell without actually holding the race and seeing the bearing. hard to know if the galling is from cascading failure or failure initiation (chicken or the egg!). perhaps improper lubrication at breakin? Something caused enough adhesion to result in the bearing sliding vs rolling.

 

[stickling9]

Good pictures, by the way. On the top picture, it looks like spalling as well, which is definitely loading related.

 

[Qjoh5510]

You're going to have a difficult time getting an educated guess with just one piece to the puzzle. In a perfect world... you'd look at all pieces of the puzzle. Which sounds like that's what they are doing.

If you could see the gear pattern after the "failure" and look at the remaining bearings you can start to understand what's going on. Without it... really tough to say what the issue is.

Will you report back with their findings?

Yes as soon as I know what they conclude I’ll report back here.

 

[Qjoh5510]

we call this 'galling' which occurs under high sliding load. Your bearings are not turning, which may be from too high preload? Hard to tell without actually holding the race and seeing the bearing. hard to know if the galling is from cascading failure or failure initiation (chicken or the egg!). perhaps improper lubrication at breakin? Something caused enough adhesion to result in the bearing sliding vs rolling.

When you say too high of preload? How is that set? They completely replaced all the bearings and gears with a new set and I have the same exact whining under the same circumstances. I wonder if we are chasing an install error that isn’t obvious because they’re just following the specs.

 

[stickling9]

When you say too high of preload? How is that set? They completely replaced all the bearings and gears with a new set and I have the same exact whining under the same circumstances. I wonder if we are chasing an install error that isn’t obvious because they’re just following the specs.

If the correct install specs are followed and since it happened twice - may be worth while to measure the housing as well. I am not well versed in diffs, but do a lot of HD trans and engines (engineer for HD off road company in the Reman world). But conical bearings typically have a loading that is torque related. But sometimes that loading is set by the assembly. However, if the housing is not holding the race correctly, it could pinch the bearing. I apologize, I really dont know enough about diffs to speak intelligently, but I do recognize the material failure

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