OpenTrackRacer

Just got back from a three week off-road trip to Colorado. Part way through the trip my front differential started making a strange noise. It was a metallic scraping. The really weird thing is that it would only start after hitting a decent bump. After that it would continue until I made a complete stop and then it would go away until I hit another bump. As the trip went on it started doing it with smaller bumps but the noise pretty much remained the same. The front differential worked normally and didn't seem to get excessively hot. The sound continued in the same fashion after I removed the front driveshaft.

I've been having ongoing issues with water contamination in my front differential. I drained the fluid on the trip and it was contaminated again. I drained it (there were no metal shavings on the magnet), refilled it, drove for a bit, drained it again and then refilled it for the rest of the trip. With the water contamination, I was thinking that the pinion bearing was probably going and making the noise.

Fast forward a few weeks. After towing the Jeep home (900 miles behind my motorhome) the sound has gone away. I've been driving it for more than a week and it hasn't made a peep. I checked the fluid and it looks fine. I hooked the driveshaft back up and still nothing. Two wheel drive, four wheel drive, locked, nada. Speaking of locked, the front locker is engaging but the light keeps flashing. This has happened before so I'm not so sure it's a symptom of anything related.

I'm curious if anyone has thoughts on this? I've ordered new gears (going from stock to 5.38) and master install kits. However, I have a trip coming up and I'm doubtful I can get the gears installed and broken in before that happens so I'm thinking of rolling with it as is. After the noise started I drove or towed the Jeep something like 1,500 miles with no issues.

Looking forward to hearing comments!

ShutterBug

Are you sure the noise was coming from the diff and not something else? Did you check your brakes (pads and calipers) for scoring?

jtphoto JK

Sounds like you had a stone stuck between rotor and backing plate or caliper. Prob bounced it loose and out while towing it home.

OpenTrackRacer

I can't be 100% sure it was coming from the differential because it's hard to get your head in there when the Jeep is moving (without losing it). I am sure that the sound was not coming from either wheel assembly. I checked the brakes and everything around each wheel carefully (wheels off). The sound strongly appeared to be coming from the center front of the Jeep, not from either side. The sound continued in any gear or neutral and with the engine off. Application of the brakes did not effect the sound at all.

jtphoto JK

IMHO if the noise went away, it wasn't in the diff. Something going bad in there simply doesn't go away..for piece of mind drain the oil and remove the cover for inspection..

ShutterBug

Could have been a stick or rock stuck in the pinion flange or rzeppa joint.

OpenTrackRacer

The front driveshaft is a Coast so no more CV joint. The sound continued even with the driveshaft removed anyway. I carefully checked the dust seal around the pinion and didn't find anything. Brakes and wheel bearings were cleared and the sound was clearly not coming from that area anyway. There's no other component in the front end that I can imagine that could make that sound and it was pretty obviously centered and not really louder in the left or the right.

That's why it's so weird.

ShutterBug

I'd take the cover off, and check the fluid carefully. Get it up on a jack stand so you can rotate one tire and check the ring gear. I still can't see it being anything in the diff, but I'm no mechanic.

jtphoto JK

So did you pull the caliper and rotor off for your inspection when you were looking for the noise. That would be the only way to ensure a stone wasn't stuck behind there.

Again, at this point , removing the diff cover for inspection would be your next step.

OpenTrackRacer

I did not pull the calipers or rotors when I was inspecting it. I did look everything over very carefully and also looked for signs of scoring on the rotors though, as well as free spinning the axles. Applying the brakes had no effect on the sound.

It's certainly not impossible that it was at one of the wheels but we did listen carefully by each front wheel and the sound absolutely did not sound like it was coming from there. It was slightly louder on the left than on the right (and of course, the pumpkin is closer to the left than the right) but definitely seemed to be coming from beyond the wheel and hub.

Since it's behaving right now I'm going to head out on my trip with everything as is. When I get back we'll be changing the gears to 5.38's so we'll get a chance to inspect everything then. If it turns out to have not been the differential I'm still okay with it because I've been meaning to change gears for years and never got off my butt to do it.