Hey all---

I see several posts here that some guys are using 5w30 Synthetic motor oil in the TC. I heard it from a local Trans shop here in town also. What's the advantage of this over AutoTrek 2 and should you really over fill the TC thru the speed sensor hole? Seems like that could promote leakage. Thanks, Gary. :chevy:

It dose not evaporate when temps get up... Search, there is a lot of reading as to why this is better, I did mine a couple months ago. Sorry i am not more of a help on this issue...

Moved to Maintenance & Fluids...

Hey all---

I see several posts here that some guys are using 5w30 Synthetic motor oil in the TC. I heard it from a local Trans shop here in town also. What's the advantage of this over AutoTrek 2 and should you really over fill the TC thru the speed sensor hole? Seems like that could promote leakage. Thanks, Gary. :chevy:

First off I don't think your T-Case calls for Auto Trak. It should call for ATF. If your under warranty still think about what fluid you use. Its has become an accepted practice to run 5W-30 synthetic motor oil in the T-Case and I can tell you it queits it down. I however didn't do the 3rd qt thru the speed sensor hole. 2 was fine for me and I check my fluid level when doing PM.

First off I don't think your T-Case calls for Auto Trak. It should call for ATF. If your under warranty still think about what fluid you use. Its has become an accepted practice to run 5W-30 synthetic motor oil in the T-Case and I can tell you it queits it down. I however didn't do the 3rd qt thru the speed sensor hole. @ was fine for me and I check my fluid level when doing PM.

FYI, my '07 2500 HD Classic owner's manual says Auto Trak II...

FYI, my '07 2500 HD Classic owner's manual says Auto Trak II...

Thats why I started my post with I don't think. Because in my 49th year I seem to be wrong more than I used to be!!!! :D http://www.allthingsmoto.com/forums/images/smilies/lol.gif

I've got to admit that I would be just as wrong as Dane (dirtbikindad393) on this one. I'm wasn't aware that the HD trucks used Autotrak fluid.

Let's be more specific. The NV t-cases are typically of two slight variants in the HD trucks, AFAIK. The 261 (manually shifted) and 263 (electronically shifted) cases as basically the same, except for the shift method. I don't think that the HD trucks use anything but this. However, I, like Dane, have been known to be wrong. Don't confuse the "electronically shifted" comment to construe it with the other electronically controlled auto-shifting t-cases.

The GM owners manuals have been known to be printed incorrectly upon occasion. And even when properly written, can be confusing at times to read.

All I can say is that if the new cases take Autotrak fluid, it's news to me.

I was under the impression the Auto Track Fluid went into the 1500, Jimmys etc and the HD only had a T-case that took ATF. The whole electronic thing is so confusing because if you have buttons on the dash as Joe Citizen you assume thats electronic shifting not so with GM. The electronic shifting deal is in the lighter weight vehicles with round push buttons and not rectangular. But.....who knows I could be wrong!

I've got to admit that I would be just as wrong as Dane (dirtbikindad393) on this one. I'm wasn't aware that the HD trucks used Autotrak fluid.

Let's be more specific. The NV t-cases are typically of two slight variants in the HD trucks, AFAIK. The 261 (manually shifted) and 263 (electronically shifted) cases as basically the same, except for the shift method. I don't think that the HD trucks use anything but this. However, I, like Dane, have been known to be wrong. Don't confuse the "electronically shifted" comment to construe it with the other electronically controlled auto-shifting t-cases.

The GM owners manuals have been known to be printed incorrectly upon occasion. And even when properly written, can be confusing at times to read.

All I can say is that if the new cases take Autotrak fluid, it's news to me.

I wonder if GM threw the AT II fuild in there for the pump rub issue? Extra additive couldn't hurt???

I'd have to admit it's purely speculation on my part at this point.

Unless something has drastically changed that I wasn't aware of, only the 261 and 263 cases are available in the 2500HD and 3500HD trucks. I've been wrong. Dane's been wrong. You've probably been wrong. GM's known to be wrong. Hell - none of us are perfect. So the t-cases themselves are probably still 261's ro 263's in the HDs.

Now, as to the issue of the AutoTrak fluid, I'll take BoiseRob at his word. Just seems odd that there'd be a change of fluids in mid-stream. It's entirely possibly that they sought out a different fluid due to the pump rub issues, but I can tell you from personal experience that my opinion is this: NO FLUID is going to avert, prevent, or otherwise avoid pump rub. If that little spring clip breaks or moves, the pump body will contact the case, and it's only a matter of time until it rubs through. Not even TES-295 (probably one of the best fluids out there for this application) would stop pump rub.

So, I suspect, with respect due to BoiseRob, that it's possible a mis-interpretation of the description of the t-case applications is coming from the language in the manual. I know that for 2006, the owners manual was all-inclusive; the manual covers 1500, 2500, 2500HD and 3500HD models. So, the description of the t-cases is somewhat muddled. It is important to know that the 1500 trucks have a t-case that can automatically engage, if slippage is sensed by the ABS system. That case is completely different from the ones used in the HD series. What you really have is three different t-cases, (and perhaps four, if the 1500 has a "manual" case). The HD's are very similar, except that one is uses an electronic solenoid that shifts; it does what my hand would do on the manual case. But the 1500 series truck t-case is very different. It's not as robust, it's not shapped quite the same, etc. It does shift electronically, but it accomplishes this in a different manner. The solenoids are different in size and location a bit. If you crawl under a 1500 with "Auto-Trak" 4x4 and look at that t-case, it clearly isn't the same as ours in the HD's.

So, when you read the GM owners manual, there are three possibilities.
1) GM actually changed the fluid spec for 2007. Seems odd to do it for one year. I've already read that 2008 and 2009 are spec'd for Dex VI. Why have AutoTrak fluid for only 1 year? Possible, but not likely.
2) GM has some manuals out there with a misprint. Much more possible than condition 1
3) The readers are mis-interpreting the "electronic" feature language in the manual, probably because GM's tech writing staff sucks, IMO.

I know that in my 2006 manual, depending upon what page you read, it says that the front differential calls out either 80w-90, or 75w-90 synthetic fluid. Talk about confusing to the un-expecting owner! While I know that the two are just overlapping weights (actual proper term is "grade"), there is room for mis-interpretation. My point is that the GM manual is not well written, even when the correct info is in there.

I suspect that BosieRob is reading it correctly, and either it's a mis-print, or it's poorly structured and easily mis-read, even by those of us who know better. It could be a one-year-only specs, but I doubt it.

BoiseRob, any chance you could scan a copy and post? You've got me mucho curious!

BoiseRob, any chance you could scan a copy and post? You've got me mucho curious!

I'll try tomorrow...