Rear Differential Fluid Issues??? Please Help

[missinglink]

I recently had to have a new transmission and transfer case installed in my 03' 2500hd 4x4, gasoline truck at 130k. I live in Arizona, where the climate conditions are extreme. Lately ive been noticing a slight grinding feeling after I've been at highway speeds for a while in the heat, and when I come to a complete stop...from 0-5 mph I can feel something chunky in my seat, feels like it's coming from the rear diff. I've never changed the fluid in it, and I probably should have a while ago. I don't tow anything, or really do any heavy duty work, but I drive a lot. So today I did what I could to change the fluid. The oil was BLACK on the way out, and appeared that there was only about 2 quarts or so coming out. I was told at the auto part store that it would take 4. I opened the drain and fill plugs to drain, when I filled it, it only took a little less than 3 quarts before it started to leak from the fill hole on the side. I don't want to F anything up, so is this something to be concerned about? do I need to do any additional work to make sure it's done properly? I can't afford another $3500 repair right now, and would really appreciate some help...thank u!

[DmaxMaverick]

That would make me nervous. It should have taken more than 2 qts. Make sure you are doing the service on a level surface while the R/E is hot (after a good drive), and allow it to drain until nothing else comes out. The axle tubes and hubs will retain some lube, and moreso if one side is higher than the other. Normal service should have been very early on. 130K is extremely long for the factory fill, which may have been underfilled initially.

The recommended fill is about 3.5 qts (about 3/4 - 1 inch below the fill hole), but will flow over at near 4 qts. The reason for the "underfill" is to prevent vent tube plugging (resulting in leaking wheel seals in some cases). I suggest cover removal and further investigation. In your climate, I also suggest using 75-140 lube (factory fill and normal duty recommended is 75-90), even though you don't tow or load, with your current situation (quality name-brand synthetic, or 5x the price for the dealer stuff -- DO NOT use traditional lube. Full synthetic ONLY). If the rear end is the source of the noise, it could be the lube was just used up. Hopefully, you didn't damage anything.

Investigate the "chunky" feeling in the seat further. It could be any of several sources. If you have a 2-piece driveshaft, suspect the carrier bearing isolator. Could also be U-joints (doubtful in your case), or tire issues. Also check the front wheel bearings (lift the wheel off the ground, firmly push/pull the top of the tire in/out--any noticeable movement indicates bad bearing or other suspension issue).

[JohnC]

03' 2500hd 4x4, gasoline truck


That would make me nervous. It should have taken more than 2 qts.
Wonder what axle we're talking about....

[DmaxMaverick]

Wonder what axle we're talking about....

GMC-10.5 or AAM-11.5, design, fluid capacity and requirements are similar. Both should be about 4 qts to full fill, regardless. 6.0L is 10.5, 8.1L is 11.5.

[MAS1866]

I'm new and can't figure how to start a newthread so I just posted this reply.
I've got a 11.5" lockup diff in a 2005 Duramax 4x4. It stays locked up when turning corners slowly even to hte point of stating locked doing a 3mph donut:(. Is it a big job to change the goveror in the carrier?

[DmaxMaverick]

I'm new and can't figure how to start a newthread so I just posted this reply.
I've got a 11.5" lockup diff in a 2005 Duramax 4x4. It stays locked up when turning corners slowly even to hte point of stating locked doing a 3mph donut:(. Is it a big job to change the goveror in the carrier?

At the top and bottom (left side) of every category forum (such as 2500HD/3500 HD Trucks & Drivetrain), there should be a "New Thread" button you can click. It will take you to a page similar to the "Post Reply" page (the page you used to reply to this thread). If you can't find the button, or have other issues with the forum, send me an email (in my signature).

The carrier isn't difficult to service, but does require some specific skill. The locked-up locker could be a couple reasons, such as the governor (or a part of it) you mentioned. The carrier has to be removed, parts R/R'd, then reinstalled. As long as you don't replace any tolerance-critical components, it should be simple with no need for a diff setup procedure (gear lash, shims, etc.) if all the remaining parts are replaced exactly as they were removed.

[MAS1866]

Talked to a couple of guys today and they suggested that the lube may be broken down. My buddy(a jouneyman auto mech) had an old 83 or so that behaved the same and all he wound up doing(after tearing it down and finding nothing wrong) was repacing oil with new stuff and limited slip additive and it worked fine. Let you know how I make out.

[DmaxMaverick]

A lube service may help. It won't hurt to try. DO NOT use L/S additive. GM trucks haven't had limited slip (from the factory) since 1994. The locker in your diff is an Eaton Gov-Loc, and requires NO additive. Only a quality synthetic gear lube, GL-5 compatible (NOT GL-4), 75-90, or 75-140 (for extreme conditions). The conditions you described at first may be related to your locked locker. Good luck!

[jmac5058]

I would not hurt to drain and refill again in a month or two.Thats a extra step I like to take when the oil is extra dirty/worn and or you cant completely drain the componet like in a automatic transmition.