Perk
New member
- Oct 23, 2026
- 2
- 0
- Current Rides
- 2023 Rubicon 392, 2015 Ram 2500 (6.4L), 2015 Jeep Grand Cherokee Limited
New to the forum - actually have been reading it for the past 6 months since I purchased my 392, lots of great info here and really appreciate all the effort members put in here to share info. I purchased a 2023 Rubicon 392 (sting grey) back in March. It had 7k miles on it and was in great condition. Only downside is that I purchased it from a used car dealer in Salt Lake area and they said it had 6 months left on the B2B warranty and 3 years/53K left on the power train. I tried to purchase the Stalantis extended warranty and thats when I found out the vehicle was from Canada - so no warranty and no ability to purchase the extended. Conversations with the dealer went no-where and I ran out of F's to give. But, I love the Jeep, funnest vehicle I have ever owned.
Ok, here is the issue. Right at 12k miles, I noticed some gear whine above 55-60mph when decelerating. Goes away immediately when I get back on the gas (tip in). It is very faint, radio has to be off and I have to listen close, but it is there and I can hear it every time I let off if I am going over ~55 MPH. If I let it coast below 45 I cannot hear it anymore. Nothing on acceleration, no clunks, hard shifts etc. I can put it in neutral while coasting and no change. I think it all points to pinion depth, so maybe the pinion nut came loose or the crush sleave collapsed some?
Here is what I have done so far:
1. Changed the Rear diff fluid, went with Royal Purple 75W-140. No shavings, ring gear looked great, did not paint the ring gear and check but contact pattern looked centered.
2. Changed the Front diff fluid, went with Royal Purple 75W-90. No shavings, ring gear looked good as well, contact pattern also looked centered. No change after either servicing both diffs.
3. Changed the transfer case fluid. Clean, no shavings, transfer case fluid looked as clean as new.
4. Dropped tire pressure from 35 psi to 32 psi - wanders less, but no change. I did this because temps had been in the 80+ range since I bought it and when I first noticed it, the temps had dropped to ~50-70 degrees, Didn't expect it to help, but sometimes I swore it sounded like tire noise (has the stock 35" tires on it).
5. Put the transfer case and transmission in neutral, got underneath and felt for play in the drivelines. Front has zero play, the rear feels like I can move it in and out (not up and down or side to side) by ~ 1mm. Cannot feel that in the front drive line. But, just trying to move the yolk in and out, I can't feel that 1 mm play, so I think there is some play within the drive line. It is hard to be 100% sure, I tried it back and fourth (driveline vs yolk) about 30 times. Drive line you have a lot of leverage, yolk, not so much, so it is difficult to tell. After 30x I was convinced the play was in the driveline, not in the pinion.
I have found a few threads in different forums where people report this. One was ugly, Jeep replaced the rear diff, then the transfer case, then the entire rear axle. The guy said after the complete rear axle replacement, it went away, but came back after 600 miles. He said he was told it was typical/normal after the gears wear in. I also found quite a few posts from Challenger, Charger and Ram truck owners reporting the same thing, many went unsolved. One owner reported giving up on it, regularly serving the diffs and no shavings etc. in any of changes. He continued to just drive it and had 90k + miles on it since and no issues.
I am on the fence, keep an eye on it (service the diffs again in another 5-10k miles) or take it to reputable offroad shop that specializes in re-gearing and let them go through the diffs. Unless of course, it starts getting worse. Any help is appreciated. And if anyone has a recommendation for the nearest-best shop for this to Boise, Idaho, I would appreciate it. Thanks in advance for your help.
Ok, here is the issue. Right at 12k miles, I noticed some gear whine above 55-60mph when decelerating. Goes away immediately when I get back on the gas (tip in). It is very faint, radio has to be off and I have to listen close, but it is there and I can hear it every time I let off if I am going over ~55 MPH. If I let it coast below 45 I cannot hear it anymore. Nothing on acceleration, no clunks, hard shifts etc. I can put it in neutral while coasting and no change. I think it all points to pinion depth, so maybe the pinion nut came loose or the crush sleave collapsed some?
Here is what I have done so far:
1. Changed the Rear diff fluid, went with Royal Purple 75W-140. No shavings, ring gear looked great, did not paint the ring gear and check but contact pattern looked centered.
2. Changed the Front diff fluid, went with Royal Purple 75W-90. No shavings, ring gear looked good as well, contact pattern also looked centered. No change after either servicing both diffs.
3. Changed the transfer case fluid. Clean, no shavings, transfer case fluid looked as clean as new.
4. Dropped tire pressure from 35 psi to 32 psi - wanders less, but no change. I did this because temps had been in the 80+ range since I bought it and when I first noticed it, the temps had dropped to ~50-70 degrees, Didn't expect it to help, but sometimes I swore it sounded like tire noise (has the stock 35" tires on it).
5. Put the transfer case and transmission in neutral, got underneath and felt for play in the drivelines. Front has zero play, the rear feels like I can move it in and out (not up and down or side to side) by ~ 1mm. Cannot feel that in the front drive line. But, just trying to move the yolk in and out, I can't feel that 1 mm play, so I think there is some play within the drive line. It is hard to be 100% sure, I tried it back and fourth (driveline vs yolk) about 30 times. Drive line you have a lot of leverage, yolk, not so much, so it is difficult to tell. After 30x I was convinced the play was in the driveline, not in the pinion.
I have found a few threads in different forums where people report this. One was ugly, Jeep replaced the rear diff, then the transfer case, then the entire rear axle. The guy said after the complete rear axle replacement, it went away, but came back after 600 miles. He said he was told it was typical/normal after the gears wear in. I also found quite a few posts from Challenger, Charger and Ram truck owners reporting the same thing, many went unsolved. One owner reported giving up on it, regularly serving the diffs and no shavings etc. in any of changes. He continued to just drive it and had 90k + miles on it since and no issues.
I am on the fence, keep an eye on it (service the diffs again in another 5-10k miles) or take it to reputable offroad shop that specializes in re-gearing and let them go through the diffs. Unless of course, it starts getting worse. Any help is appreciated. And if anyone has a recommendation for the nearest-best shop for this to Boise, Idaho, I would appreciate it. Thanks in advance for your help.
