Rear diff initial fluid change and ???

[pscott]

All,
I have a 2004 Dmax 4X4, and I was wondering when I should change my rear diff fluid the first time, and what should I use? I rarely tow anything...

I have heard of people using some purple synthetic that is supposed to be very good, but very pricey?

[JD Diesel]

Amsoil severe service 75 90 is very good should change now I think it takes 3Quarts. Price around 10 a Quart :D

[ifishinxs]

I have an 05. I just changed mine out at 5,000 miles..I used Valvoline Syn 75-90..It took 4qts and it is just shy of the fill hole.

When I drained the oil stuff out I measured it and I came out to 2 1/2 qts..So I got short changed from the start. The stuff that came out smelled like crap with a slight grape smell to it...

[TJ Moose]

Ha! I have a '95 3/4 ton Sub and just recently changed my rear diff fluid for the second time at 180K miles. (Ooops. I wouldn't recommend waiting that long.) Fortunately - looked okay and wasn't burned - I lucked out. Easy for me to get Royal Purple from my local NAPA, or Red Line from another parts place 2 blocks from the house (I used the 75-90 wt). I'd use either. Synthetics good for lots of reasons - main one being it'll take higher temps before breaking down - gives you a little leeway for hot weather or hard tows. Prices comparable to each other. Don't forget the T-case if you're doing fluids. That thing is rolling all the time too. Make it synthetic there too.

[clifcotim]

I just paid $90.00 for 3 quarts of the GM syn from the dealer to change my '05 D/A at 3800mi. Saw nothing in the removed fluid so it may have been a waste of money, but I do feel better about going to the S.C. coast for vacation.

[DA BIG ONE]

Originally posted by TJ Moose:
Don't forget the T-case if you're doing fluids. That thing is rolling all the time too. Make it synthetic there too. YOU ARE RIGHT!

If it is a NP 246 t-case everything up and into the differential rotates "except the axles themselves."

I had found tech manuals stating the clutchpack on the NP 246 dis-engages when not in 4 wd, and that the autotrac controller engages/dis-engages clutch pack, "not true", as the clutchpack is always engaged w/springs keeping it clamped.
"Reason for the clutches is to reduce shock/damage at the front axle."

Heat builtup is high because of NP 246 rotating always, so I suggest synthetic in front axle/trans/t-case & rear diff.

[Mike Simjack]

Then why is their not a recomended diff service in the owners manual???


2003 2500 hd 2wd durmax

[madmatt]

the factory fill is syn. and is supposed to be good for the life of the truck. I don't advise one way or the other but I've never seen a failure that could be atributed to not serviceing the diff. diffs are pretty tough anyway and in my opinion, as long as you've got some kind of lube in there it will be fine.
FYI the GM 11.5 will run 3-4 days w/ no lube in them....don't ask :(

[SLT556]

For those with electronic push-button 4x4, I beleive you are supposed to use GM AutoTrak II.

[DmaxMaverick]

Originally posted by SLT556:
For those with electronic push-button 4x4, I beleive you are supposed to use GM AutoTrak II. "Electronic" and "push button" are not the same.

If you have "Auto 4 x 4" (electronic), then you need Autotrac II fluid. If you do not have the "Auto 4 x 4" button, then use ATF. The "Auto 4 x 4" button is a larger round button at the top of the button cluster. All others have only square buttons, all of the same size. Using the wrong fluid can cost you a transfer case in a hurry. Either one. "Auto 4 x 4" is only available on 1500 and 2500 rated trucks. The 2500HD and 3500 trucks do not have this option. All 2500HD and 3500 trucks require only ATF in the transfer case. I know it sounds like I'm beating this to death, but it can be quite confusing. I'd hate to hear (again) of someone grenading their transfer case because the wrong fluid was used due to this misunderstanding.

[bgaiche]

I just changed my rear end grease. Has 23,000 on original grease. It was blackish in color. It seemed to me that it needed to be changed. I poured the old oil back into empty containers and there was only 2 1/2 quarts. I filled it to the drain hole and it took 4 quarts. I used Mobile Syn. 75/90.

[DA BIG ONE]

Originally posted by DmaxMaverick:
</font><blockquote>quote:</font><hr />Originally posted by SLT556:
For those with electronic push-button 4x4, I beleive you are supposed to use GM AutoTrak II. "Electronic" and "push button" are not the same.

If you have "Auto 4 x 4" (electronic), then you need Autotrac II fluid. If you do not have the "Auto 4 x 4" button, then use ATF. The "Auto 4 x 4" button is a larger round button at the top of the button cluster. All others have only square buttons, all of the same size. Using the wrong fluid can cost you a transfer case in a hurry. Either one. "Auto 4 x 4" is only available on 1500 and 2500 rated trucks. The 2500HD and 3500 trucks do not have this option. All 2500HD and 3500 trucks require only ATF in the transfer case. I know it sounds like I'm beating this to death, but it can be quite confusing. I'd hate to hear (again) of someone grenading their transfer case because the wrong fluid was used due to this misunderstanding. </font>[/QUOTE]Your beating nothing if you can save some grief!

Not long ago I had a new, not rebuilt NP 246 AutoTrac t-case installed been using 100% synthetic fluid for about 30K now, but now wonder if I'm asking for trouble?

[mark45678]

I tell every one " change your fluids early"! both my 01 and 2004 had a good amount of metal in the tcase oil and rear end! for the money I think its well worth it! my buddie has a 2001 3500 dmax/ allison , at 120K he needs a compleat over haul on the rear end.... I asked him if he ever changed the fluid , he said no! the ring and pinion is right around $400 for just the parts, I rest my case!

[mbowerma]

I just changed my rear diff used valvoline. Same story as quite a few others only 2 quarts in rear diff. Specs say holds 4 quarts. This was done at 22000 mi. no leaks. So what amount does the factroy put in? and if its 4 quarts where does it go?
Anybody? :eek:

[DmaxMaverick]

The service fill should be about 3 qts. It was ammended after several complaints of seal leaking. The ammended fill seems to have helped.

I don't know why they are being delivered with only 2 qts. Perhaps the initial fill of "whatever" doesn't take into acount that some of the lube will remain in the bearings and axle tubes when it is drained. I can't imagine that a whole qt is being held in there, though. Probably just the bean counters making up some beans. It doesn't seem to be hurting anything.

[Black95TD]

Good Evening,

I recently checked my fluid in the diff of my 99 Suburban 1500. No leaks visible and yet it was VERY low. Don't know where it went but it disappeared. I'm a new beliver in checking all the fluids. I did only this after my brother ruined a rear end in an explorer becuase of low fluid.

My .02