TJ Rubicon coast noise

[JedGrant]

Hey all, I’m getting some mostly coast noise out of the front D44 on my TJ. I installed a Nitro 5.38 gearset about a year ago and pulled it apart today to diagnose the noise.

Current specs:
Pinion+carrier preload is around 8 in/lb. Range according to Nitro is 6-9 (albeit only for the pinion).
Backlash is slightly high at 14 thou in a range of 6-10.
Wear pattern looks pretty good, coast side might be a little high on the heel but the drive side is in a good spot (photos attached).

Thoughts? I don’t mind pulling the carrier and checking the pinion bearings but I didn’t want to do this needlessly. Is the backlash too far out? Should I go ahead and double check pinion preload alone?

Wheel bearings are less than 2 years old and are tight. Am I missing anything?

 

[Chris_Keziah]

Hard to see the coast side pattern but from what I can see on the drive side it appears to be shallow. If that's the case then you may need to blow it apart and address the setup. I'm sure @Jody Treadway who is exponentially more knowledgable on this than I am will chime in but if it were mine I'd pull it apart and address the setup. You have any paint so you can run a pattern?

 

[JedGrant]

Hard to see the coast side pattern but from what I can see on the drive side it appears to be shallow. If that's the case then you may need to blow it apart and address the setup. I'm sure @Jody Treadway who is exponentially more knowledgable on this than I am will chime in but if it were mine I'd pull it apart and address the setup. You have any paint so you can run a pattern?

I don’t have any paint, but I also need to order a shim kit for this and another project so I’ll pick up some paint when I do. The photos might be a bit deceiving, I think the depth is ok but I can measure that tooth engagement to see what percentage of the face is meshing. Looking it at in person, there’s about 80-85 percent of the flat face in contact (or at least was in contact at some point; paint will tell if it’s still in contact).

 

[Jody Treadway]

Coast or decel noise is due to a shallow contact patch (if it's gear related) or a loose pinion nut and/or worn pinion bearing.
That BL being so far off won't necessarily cause decel noise, but it will cause accelerated gear wear.
That ring gear looks quite worn. I'd suggest a fresh gear and bearings.

 

[JedGrant]

Coast or decel noise is due to a shallow contact patch (if it's gear related) or a loose pinion nut and/or worn pinion bearing.
That BL being so far off won't necessarily cause decel noise, but it will cause accelerated gear wear.
That ring gear looks quite worn. I'd suggest a fresh gear and bearings.

I guess it’s the shallow contact patch then because everything else looked ok. I’ll just plan to rebuild the whole diff (sans ring gear bolts) next year since a shim kit is over half the price of a rebuild kit. I don’t drive it a lot so it isn’t hurting me to let it sit for a while. I did change the gear oil to a lighter 75w140 from an 80w90 so we will see what if that makes any difference.

The gears are fairly new, I think the worn look might be a photo issue. In person they don’t look or feel like that photo makes it look like. I’ll compare these photos when I do the new master kit and will make the choice then.

Thanks for your help!

 

[OnlyOneDR]

Jed just give the Jeep to me and cut your losses. When you say "coast noise" that is pretty much all the time for a front axle. Can you actually hear the noise go away in drive when you have it the transfer case in 4wd? To me 8 in/lb sounds too light for total pinion + carrier preload. Can you detect any axial play in the pinion?

Also, don't forget about those u-joints in the driveshaft. You can try leaving the shaft out and taking a drive to see if the noise goes away; if the u-joints have never been replaced it might be time to.

 

[JedGrant]

Jed just give the Jeep to me and cut your losses. When you say "coast noise" that is pretty much all the time for a front axle. Can you actually hear the noise go away in drive when you have it the transfer case in 4wd? To me 8 in/lb sounds too light for total pinion + carrier preload. Can you detect any axial play in the pinion?

Also, don't forget about those u-joints in the driveshaft. You can try leaving the shaft out and taking a drive to see if the noise goes away; if the u-joints have never been replaced it might be time to.

Hey Chris, sorry for missing this till now. I think the gears are shot but I haven’t been back in to check it. I probably didn’t push the pinion deep enough and that coupled with the backlash has ruined the gears. U-joints are new, and it has been making the noise before and after changing them last year. I’m going to pull it all apart again this spring and take a better look when I have the downtime available.