Finally got around to changing the t-case fluid today. Have a question about capacity though... according to my service manual, it should take 7 pints or 3.5 quarts of Dexron III, however, upon refill it started spilling over at about 2.5 quarts. Is this a wet/dry issue, or maybe a typo in the manual? I'm pretty sure I drained the thing completely before refill...

Recheck the level again after driving a few miles. If it is at the right level you are probably OK.

The good news is that the fluid looked new - clear, reddish, no smell. I'm guessing the last change was at about a year and roughly 13.5k miles ago (judging by service records of the previous owner). This past weekend we did a lot driving in the White Mountains in NH at highway speeds, so I'd guess the t-case got a real workout with no apparent problems.

When coming down Mt. Ascutney on Sunday I'm sure that the tcase/tranny gets hotter going down than up! Wonder why?

Another question, just how bad is overfilled transmission fluid? The manual warns against this, and mine seems a little high, but seems to be operating fine. And where's the drainplug? The manual shows it on the pan, but I can't find it at all...

If slightly overfilled you are probably OK. The problem that GM wants to prevent is foaming of the fluid, which can happen when overfilled.

Remember that the level is very tempature dependant, so it can vary, too. I've found that transmissions are the hardest thing to get right, and that 4L80E is one of the worse ones that I know of! Especially after filling it, since then there is a lot of fluid on inside of the fill tube that confuses the readings! I do it this way, get the truck hot, and check the level. Drain the transmission, change the filter. Figure a small amount of lost fluid (in the filter, etc.) and then measure the amount of fluid drained (I've a bunch of old oil bottles that I use). Refill with the same amount taking into account the lost fluid (in the filter, etc.) too. That will get you close enough for the day. The next day drive it, say 20 miles, then re-check. Should be easier to check as the tube won't be full of ATF like it is after a fill!

No warranties expressed or implied on that one!

Oh, and not all trannies have drain plugs. Mine does (thank goodness), but if you don't have one, you can get one welded on to the pan if you want.

Peter Hipson
Founder New England Hummer Owner's Group (NEHOG) the free Hummer Owner's group!
1995 White NA Hummer Wagon