Rear Axle Fluid Level

[JohnnyR]

Checked the differential fluid level on my 2005 GMC 2500HD Duramax yesterday and found it to be 1-inch below the fill hole. Manual says zero to 1/2 inch below fill hole. Truck has about 2800 miles on it and I've towed my 5th wheel once for about 250 miles. Started to drain and change it but wondered whether that level of fluid could have damaged the rearend. No whine or any noise from rearend. Seems I remember reading in the forum that the fill level has been altered/lowered recently.

[mark45678]

I would say you have nothing to worry about.... found the front end on both of my trucks almost a qt low after dealer "prep" .... it holds about 4 qts in the rear if I recall.

[norskeman]

The rear end comes with about 2 1/2 quarts from the factory.

Takes about 4 quarts to fill. Must use synthetic fluids.

Should be changed after 600 miles of towing.

2005 Chevy Silverado 3500 LT SRW; Crew Cab Long Box ; Duramax (LLY)/Allison; Luverne stainless steel running boards; Isspro gauges; Super Duty Air Lift air bags; Bed Rug bed liner; Prodigy Controller; Husky 16K Hitch; Handy Fifth Wheel tail gate.
Towing a 2004 Everest 291L 5th wheel

[JohnnyR]

Thanks for the comments. I'll probably run it by the dealer and let them top it off just to go on record that it was low in the event I have problems later. Then I'll come home and change it. But why are they coming from the factory at so low a level?

[madmatt]

the fill spec is 3.1 qts. it's measured in at the plant and I'd imagine the axle is dry when filled and the fluid your "missing" is in the hubs. when checking the rear level, it should be 1.4-1" below the hole.

[JohnnyR]

Is there a TSB that changed what the owner's manual says, i.e. 0 to 1/2 inch below fill hole?
When I asked that question at the dealership, they were oblivious. I took it in yesterday and they said they added 1/2 quart but I didn't check to see how far below the hole it is now. I'm pretty sure 1/2 qt. would not have filled it up but it may have gotten closer than 1-inch.

[JohnnyR]

How warm should the differential be running empty in 95 degree Houston heat. Checked mine the other day after driving about 40 miles, and you could hold your hand on the differentail cover but it's somewhat uncomfortable. Axle tubes were warm but noticeably cooler. Perhaps I'm just being paranoid after finding the low fluid level... Would appreciate input.

[madmatt]

yes there was a bulletin on this and no it doesn't sound like any damage has been done. I've personally redface.gif seen a rear diff go about three days w/o any fluid in it.