Situation: Went on a 2000+ mile trip, did some light wheeling in Moab. 2 days and 500 miles later front diff started whining. Mainly 50-55mph and 70-75mph. Immediately topped off all 3 differentials. Rear and center were fine. Front took about 1QT.. So it was very low. After filling, no change in noise volume or pitch. Dropped front driveshaft and drove around with center locked, noise 100% gone. Drove home 1000 miles like that.
Changed the fluid as soon as I got home. Lots of sludge, no large chunks.
Put in 75W-90 Motul Gear300. Drove 300 miles in RWD (no front driveshaft, no load on diff). Then changed fluid again, fluid and plug were clean This time put in 85W-140, and reinstalled the front driveshaft. Whine was quieter when cold, but perhaps louder when hot. Put on 250 miles. Changed fluid again, fluid and plug were clean. Put in SAE90 Hypoid conventional, back to original noise pitch + volume.
My best guess is that this was pinion bearing failure. Decided a rebuild was necessary, so I dropped the front diff and opened it up. No debris inside. Findings:
So my question is whether I need a new ring and pinion or not. Or how to determine that myself.
The teeth feel much smoother than they look in the photos due to the light, but I'm not sure if I've worn through the case hardening or not.
Any help would be appreciated!
Changed the fluid as soon as I got home. Lots of sludge, no large chunks.
Put in 75W-90 Motul Gear300. Drove 300 miles in RWD (no front driveshaft, no load on diff). Then changed fluid again, fluid and plug were clean This time put in 85W-140, and reinstalled the front driveshaft. Whine was quieter when cold, but perhaps louder when hot. Put on 250 miles. Changed fluid again, fluid and plug were clean. Put in SAE90 Hypoid conventional, back to original noise pitch + volume.
My best guess is that this was pinion bearing failure. Decided a rebuild was necessary, so I dropped the front diff and opened it up. No debris inside. Findings:
- Pinion preload was essentially zero. Less than 0.5 in/lb
- Pinion rotation is smooth, not notchy.
- Pinion didn't have any play that I could feel.
- Pinion runout seemed to be in spec
- Not 100% sure that I measured this properly though.
- Ring gear runout was definitely in spec
- Backlash was 0.007" - 0.0075"
- Coast side of ring gear looks perfect
- Drive side of ring gear has a noticeable wear pattern. It looks worse in photos than it does to my eyes.
- The worn part of the tooth is only slightly rougher than the surrounding area. Still smooth.
- I haven't pulled the bearing caps yet, but all measurements have been in-spec except for the pinion preload.
- Here is a video with more angles and different lighting of the gears.
So my question is whether I need a new ring and pinion or not. Or how to determine that myself.
The teeth feel much smoother than they look in the photos due to the light, but I'm not sure if I've worn through the case hardening or not.
Any help would be appreciated!
