Rear Diff Cover looks scorched!?

[Scooby]

I was looking under the truck and noticed that my rear diff cover appears to have a scorched pattern on it. It feels almost rough, kinda like the precursor to rust. It also appears to be localized in a particular spot and in a pattern - it is just to the left (drivers side) of center and if memory serves me correctly, isn't that right where ring gear is?



Anyone else experience this? I'm swinging by the dealer in the a. m.



I only have 5500 miles and maybe 800 of that is with a Lance slide in camper that weighs about 4300 lbs or so.

 

[MichaelWright]

Did you check the fluid level? Some have come from the factory on the low side. Just a thought.

 

[Joseph Donnelly]

Backlash spec is . 003-. 010". If yours is at the tight end, the gears run hot. I like . 006" best; easy to reset on the AA diff.

 

[Scooby]

I swung by the dealership and they checked the shims, fluid, etc. using a scope. Apparently they can do that through the filler hole. They claim everything looks good and that the rough spot is just there because the paint on the American axle is just really thin.



Does this sound right???

 

[Joseph Donnelly]

If the dealer can see the shims, call him Houdini. The backlash is set with adjuster nuts, not shims on the AA. Pinion shims are not visible even with the cover off.

 

[Bill Stockard]

I swung by the dealership and they checked the shims, fluid, etc. using a scope. Apparently they can do that through the filler hole. They claim everything looks good and that the rough spot is just there because the paint on the American axle is just really thin.



Does this sound right???

The paint on my rear differential cover is bubbled up like heat may have loosened the paint. However, on close inspection, it's the poor paint job on the cover. I don't think AA spends much time cleaning the steel cover before applying the paint, what little there is.



When the rear differential service interval comes up, I'll "fix" the poorly painted cover with a Mag-Hytec cover.



Bill

 

[LesStallings]

Poor paint

My cover looks bad too.



I've had regular differential service and all is good inside. With over 50K towing miles on my 2004, I think it is a poor paint job with a little heat and a little corrosion making it look like *****.



When I get a chance, I'll bead blast the cover, prime and paint it with some high temperature paint... Maybe I can justify a DIY power coating setup... . !!

 

[roperteacher]

I had the same problem and I posted it on here. SOmeone suggested high gloss BBQ paint. SO I went ang got some. Just painted right over the old job, and it still looks great! Worth a try and it was 2. 99 at the hardware store!

 

[Doubleclutch]

Hmmmm... Probably a good idea to drive around a bit, then put the old five fingered thermometer on the pumpkin before breaking out the VHT BBQ black. Cheap diagnostic that will let you sleep at night without that lingering whisper of doubt. How tight was your backlash Joe?

Greg

 

[thejeepdude]

When I get a chance, I'll bead blast the cover, prime and paint it with some high temperature paint... Maybe I can justify a DIY power coating setup... . !!

That's what I plan to do with my cover at the first change. I got some crinkle powder coat that I will apply with my $99 powder coating rig from eastwood. So far all I've PC'd is the throttle box on my boat, but it came out awesome. We use an oven that someone was giving away for free, mounted on castor wheels with a mini spray box on top. Not bad for so cheap... I never paint anything metal and small enough to fit in the over anymore... PC is just too easy and lasts sooooo much longer. I think the cover will come out nice!

 

[Scooby]

Thanks for the replies - I just went camping for the last time before winterizing it [the camper] and I should have felt the cover right when I pulled in.



I didn't know there weren't any shims in the AA diffs... . I guess the ones I don't have are set just perfectly according to the dealer!



I'm thinking MagHytek like I had on my 2001 rig - as soon as the wife lets go of the checkbook.



In some wierd way, I guess I'm glad I'm not the only one who has experienced this. A home powder coating system, eh???... . I like that idea!

 

[Cattletrkr]

Just a thought...

AFTER I bought my Mag-Hytec rear cover I read on PML's site that powder coating actually retains heat. Not sure if it's enough to make a difference, but it kinda makes sense. I'm probably gonna go with PML on the front. If I gotta change them fluids every 3-4 mos. I want a drain plug BEFORE I strip the threads on the axle. :--)

 

[GTX]

The paint on my trucks rear diff cover looked like it was burnt off when it had about 2400 miles on it. The gear oil also smelled burnt. I took it to the dealer and they said that the paint had just fallen off and the smell is normal.

They said AA leaves the axles outside un-painted until they have enough in the pile to ship an order. Then whatever manufacturer gets them will paint them without cleaning the rust off. They also claim there was no damage to the gears without taking the cover off.

 

[Mark Craig]

Scooby,



We see this all the time, more so on the Ford's than the Dodge's. True the quality of the paint and the lack of primer helps create the paint peeling problem, but the diffs tend to see some pretty good temps as well, especially if you tow much weight.



We sell proabably 90% of the PML covers we do just because of folks looking at the diff after their first good summer time tow and they see the naked steel and or rusted factory cover. PML does have powder coated covers but we do not stock them as the powder coating is a very good insulator, which isn't what you really want to do to lower fluid temps etc. Plus the covers have the advantage of easy fluid changes, magnetic drain plugs and ports to add a diff temperature gauge if you want to.



Mark @ DPPI