Rear end capacity

[Grizz272]

I am coming up on the 500 mile mark on my GMC 2500HD. I have done on rear end and came up empty. How much syn 75w90 does the 3.73 rear end hold?
This truck is awesome! :D

[rtquig]

Should be just about 4 quarts.

[TraceF]

I plan to use a fully synthetic Pennzoil 75w90. Do we still need to add the 4 ounce bottle of GM limited slip additive like with the GM Corporate l/s units or will the new diff work OK with the l/s additive in the Pennzoil?

[DmaxMaverick]

No additive.

The rear end in the 2500HD and 3500 is not a traditional limited slip. The manufacturer (American Axle) states that no additive is needed. Using an additive may cause performance problems with the lube.

If your rear end hammers or chatters (like traditional L/S), don't add anyting. It's broke.

[hoot]

DO not use any additive.

They are designed to use synthetic gear lube as in original OEM.

Some of us have made the switch to aftermarket sythetic like Amsoil, RedLine etc.

I'm using Red Line and the rear has not been giving me any grief. My 97 HD with the 14 bolt full floater used to chatter bad after a highway cruise then a turn off a ramp. It required additive but the new ones don't.

[JimWilson]

Depends upon whether or not you have the dmax/allison combo. If you do then it's about 4 quarts, but if you don't then it's a hair under 3 quarts. I switched to Amsoil at the 3K oil change.

[hdmax(mike)]

Jim you are not completely correct. Both the Duramax and 8.1L big block use the 11.5" differential that use 4 quarts. The 6.0L is the only one of the three that use the smaller 10.5" differential and it uses about 3 quarts.

[TraceF]

Boy, this is complicated. The PZL lube has limited slip additive IN IT as does every syn 75w90 GL5 that I am aware of. Do GM, Amsoil and Red Line make a synthetic 75w90 specifically without it? My guess is no but I want to be sure. Wouldn't give goat milk to my baby. Thanks all!

[TraceF]

Put in the PZL 75w90. Also 10 qts. Delvac 1300 and $6.62 oem oil filter. Then gave it a wash. Drove it. Got that new truck feeling. Man, I love this beast.