Looking for some info or advice here. Have an '02 2500HD 4X4. Following a very cold spell here in February (temps below -20F), I noticed a higher pitched noise, a howl, coming from the front end of my truck. It wasn't too loud and I believed it was just my tires singing. This was at 35K miles. A couple of weeks later, the noise seemed a little louder and I became concerned - stopped in at my dealers and the tech drove the truck and also believed it was a loud tire. Truck had 37K on it at this time (no extended warranty). Tech advised me to change front diff fluid to synthetic for cold weather operation per GM recommendation. Told me that they change every truck on the lot over to syn when they get it in. This after they had to replace a couple of diffs. on vehicles with less than 200 miles on them. He also told me to rotate the tires and see if the noise changed. The dealer did document my visit.


I have since changed to syn fluid, changed the vent to the white one, and rotated the tires. The noise did not change, and actually seems louder. The noise changes in pitch and volume with vehicle speed, independent of engine speed. The noise is not changed by shifting into or back out of 4wd. The noise stays the same when accelerating, decelerating, or coasting. Braking and turning does not affect noise. Hitting bumps in the road causes a slight decrease in volume as the vehicle lifts up over the bump. The noise is the most pronounced between 30 - 40 mph, but is audible at slower speeds. It used to fade completely away above 50 mph, but is now audible up to 60 mph. I now have 40k on the truck.


Here are my questions - I've reviewed my Helms' manual and the dianostic section seems to point to a bad or out of adjustment ring and pinion. As I'm beyond the 3/36 warranty, am I totally hosed or with the known issue with cold weather - dino fluid problem do I stand a chance of some consideration from GM? Can I find out if GM will assist in the repair before it is done or do I battle it out afterward? I've looked at the adjustment and replacement procedure and it looks like it takes a whole raft of special tools so it's beyond my ability. As an option, I could replace it with a low mileage used unit I suppose, but would prefer a dealer-repaired unit. Any idea of the cost of such a repair?


Thanks for the help!


Don

It sounds like there might be damage to the differential side bearings or pinion bearings since the noise is constant. A ring and pinion noise should change under load and coasting. You might be able to take it back to the same place and speak with the service manager about covering the repairs or at least some of the cost since you took it in for this complaint before your warranty was up.

Along the same lines As Sid says ,at 37,38 K your barely out of warranty and normally GM will step up to the plate an honor the repair or part there of ...


Be respectful as possible to the service arena and they should also go to bat for ya ...





Mac





Edited by: Mackin

Depends on what's really wrong. If you took it in while it was under warranty for that problem and they didn't fix it... you could hold them to it and say "I knew it was screwed up while it was still under warranty". I've done that before and had an entire A/C system replaced out of warranty, for free. It's called pre-existing condition.

Actually the front dif is pretty easy to work on. It's got threaded adjusting sleeves to adjust ring backlash so you don't have to deal with shims. You do need to be able to press bearings though which is most likely the reason for the noise.

This is basically what it looks like... I changed the ring and pinion in a K1500 before.

http://www.dieselplace.com/forum/uploads/Z48_89ck4.JPGEdited by: hoot