Differential noise

[CoyleJR]

Earlier today I was turning into a truck stop in Kingman, AZ when I started hearing a loud clunking sound coming from the rear differential. I was pulling my fifth wheel RV with my '06 D/A at the time. I heard the clunking about ten times. I pulled over and checked the mag-hytec and magnetic dipstick. It indicated the differential was full of clean gear oil with only minor steel filings on the magnet. I drove to a nearby RV park. I did not hear the clunking noise again.

I disconnected the RV and took the truck for a drive, but I could not duplicate the loud noise. Tomorrow I am going to pull the differential cover.

Does anyone have any thoughts about what the cause of the noise could be? It was really loud and shook the truck. I thought at first that I lost a wheel. All wheel lug nuts are tight.

[JohnC]

OK, for once I really hope I'm wrong, but....

It could have been a tooth from one of the gears passing between the ring and pinion....

I suppose it is possible that something made the G80 lock up, but... Were you turning sharply at slow speed? Any chance one of the wheels slipped on some sand or something?

[jblather]

Maybe it didn't come from the rear diff. Maybe it came from someplace else?

[CoyleJR]

Yesterday, I pulled the differential cover off and found nothing other than clean fluid and normal wear steel filings on the two magnetic plugs. The problem definitely was in the differential. When you walked next to the truck in a turn (which I did with my wife driving) the entire differential was jumping and sunded like teeth breaking off of gears. I thought that the spider gears would be broken when I pulled the cover, but they were fine. I also checked the wheel bearings, U-joints, and loose wheel lug nuts (nothing wrong).

I have now driven about 150 miles pulling the 5th wheel over the mountains from Kingman to Flagstaff and have had no problems. For some unknown reason the G 80 limited slip unit must have acted up and is now operating properly. I guess that I will just have to wait and see if it happens again.

Thanks for the replies.
John

[DmaxMaverick]

John is probably right. Somehow, the locker (NOT limited slip) engaged, and stayed that way. Nothing to worry about, unless it continues to do it when it shouldn't. The Eaton Gov-Loc used in late model GM trucks operate opposite that of a Detroit locker. It remains open until a wheel speed differential is detected (approximately 100 RPM's, which is very little, really). Once locked, it will remain locked until the diff is unloaded (driving straight). While locked, it can "hammer" while turning, if there is enough traction at both wheels, or can scrub the tires if traction is broken. This is a normal condition. If this has happened only once, I suspect as John said, you somehow got one wheel turning enough faster than the other, and it locked.

The alternative is having an open diff, or a less effective (whimpy) limited slip diff. They are real good at getting you stuck, then fail miserably at getting you unstuck.