Rear dif cover paint flaking @21K.

[j080808]

I was just washing my new to me 06 2500 Duramax and noticed all the paint is flaking off the dif cover. Could this be from heat or potentially just bad paint prep. Of its 21000 miles this truck has towed a 5400# boat for ~5000 miles (freshwater launches only). Rear dif service with proper fluids/additives was done at ~10000 miles. Any ideas?

Thanks much

[tufcj]

Must be bad prep/paint. ALL the paint was gone on my 03 last fall. I pulled the cover off while changing a bad axle seal (not required, but I was changing fluids too). I cleaned it with a wire brush and shot with black Rustoleum. It's holding up so far.

Bob
tufcj

[DmaxMaverick]

If you did any significant heavy towing during those first 10K miles, it probably cooked the paint off. The recommended initial change (contrary to GM's recommendation) is much sooner than 10K for no towing, and even sooner than that for towing. This is provided a proper break in was done. I've seen a lot of these diffs during break in, and the paint failure can be very accurately predicted/reproduced, according to use and the change periods.

This is not to say there isn't a paint quality at play, as well. Could be either, or a combination of both.

[j080808]

If you did any significant heavy towing during those first 10K miles, it probably cooked the paint off. The recommended initial change (contrary to GM's recommendation) is much sooner than 10K for no towing, and even sooner than that for towing. This is provided a proper break in was done. I've seen a lot of these diffs during break in, and the paint failure can be very accurately predicted/reproduced, according to use and the change periods.

This is not to say there isn't a paint quality at play, as well. Could be either, or a combination of both.

Thanks to both for your insight!

[tufcj]

Mine didn't cook off due to towing. Mine never towed or carried more than 2000-3000 in the bed until it had over 15K on the clock. At that point, I pulled a 5th wheel on several short trips of less than 100 miles. At a little over 30K I started doing long hauls (1000 plus miles) with a trailer weighing 7000-8000.

Mine has always had a little rear end whine on coast, but the dealer says it's acceptable, and it hasn't gotten any worse.

Bob
tufcj

[DarylB]

Bought my 07 classic with 2500 on the odometer, it was flaking when I changed the diff fluid @3k. I think the truck sat on the lot for quite a while - a lot of surface rust on the front spindles, and other exposed places (driveshaft).

[Roy W]

I broke mine in carefully and changed the fluid to 75W140 at 5000 miles. It is used frequently for towing with some trips as much as 4000 miles. Mine started flaking off at 20K, but is more like undercoating than paint. The strange thing is however, the only place on the cover that flaked is that part that is exposed to the gear lube. The outside edge bolt flange that is in contact with the cast iron housing looks like new. I'm sure the cast iron housing acts as a heat sink for that part of the cover in contact with it. My immediate reaction is the gear lube was running hot, but I have since primed and painted the cover and all is okay.

[j080808]

I broke mine in carefully and changed the fluid to 75W140 at 5000 miles. It is used frequently for towing with some trips as much as 4000 miles. Mine started flaking off at 20K, but is more like undercoating than paint. The strange thing is however, the only place on the cover that flaked is that part that is exposed to the gear lube. The outside edge bolt flange that is in contact with the cast iron housing looks like new. I'm sure the cast iron housing acts as a heat sink for that part of the cover in contact with it. My immediate reaction is the gear lube was running hot, but I have since primed and painted the cover and all is okay.

Wire brush, some primer and high temp paint?

[Roy W]

Yep.........wire brush.......Krylon primer......Krylon semi flat black regular spray paint.

[j080808]

Yep.........wire brush.......Krylon primer......Krylon semi flat black regular spray paint.
Thanks much

[Mark Rinker]

I drove the '05 Crew K2500 home from the dealership, put a 30' trailer behind it, and started pulling stuff around. Within the week, my 8,500# boat went 700 miles at about 65mph.

The rear diff fluid was changed at 5K miles to synthetic. The daily towing regimine continued. The paint held up well until the first winter, then started flaking.

I thinks its a combination of internal heat and external weathering.