Transmission Fluid Mysteries

[radbad]

Hi guys,

Working on replacing fluids. Engine Oil, Differential Gear Lube, Hubs, etc. were easy, but Transmission fluid is throwing me for a loop!

First off, the military puts engine oil in the transmission. My goal is to switch to Allison's recommended fluid, TES-295. The plan was simple enough - drain old fluid, change filters, add new fluid. The execution is an ongoing nightmare:

1. Purchase new fluid: 11 gallons (43.3 quarts, according to the manuals) for $430! holy crap.
2. Drain fluid (expected about 10 gallons): Only drained about 2.5 gallons after draining from the transmission control module and the transfer case, as directed by the manual
3. Assume the military had underfilled the tranny.
4. Add 7 gallons (4 fewer than the volume listed in the manual). At this point, we were operating under the assumption that the fluid gets pumped all throughout the trans and will read lower on the stick when warm. This was based on some internet reading. We neglected to check the dipstick, which has a cold=level indicator.
5. Drive the truck around to warm it up and check the level. The level was higher than the hot-full line. At this point, we saw the cold-full line below the hot-full line and pooped our pants.
6. Drain fluid - still looking nice and red, indicating that there wasn't much oil left after our first drain.
7. Change filters
8. Replace fluid - using the cold-fill line. It took only 2 gallons.


Open questions I'm hoping you guys can help with:

1. How much fluid the trans is supposed to take during a fluid change?
2. Is my dipstick reading incorrectly? Not good to have the wrong amount of transmission fluid!
3. Does the "cold full" line only read correctly after the first drive? i.e. Is there some volume of fluid that stays up top somewhere after being pumped around the first time?

Thanks guys!

PS. edited for clarity and some typos.

 

[Suprman]

Trans and mated transfer case share fluid but I don't know how much stays in the tcase.

 

[Overdrive]

Question radbad... Did you have to remove the front driveshaft at the trans side to get the driver's side filter out? The procedure in the -20 says that is required.

My 97 LMTV was about 3 quarts overfull when I got it from GP. Warmed up to operating temps, drove around for about 10 minutes then kept running and checked dipstick. Drained off three quarts, a cup-full at a time from the oil sample valve (these work great without having to raise the cab by the way) until trans level was just below full hot. Just drove 120 miles yesterday going to inspection station then DMV for registration and plates then checked trans dipstick again and it is still just at the full hot mark. No milkshake or contamination in the trans oil (mine still has the engine oil in trans) so it was simply overfilled by someone.

The engine was 4 quarts low which I am guessing someone put the extra oil in the trans instead of the engine the last person who attempted to service the truck.


It is my understanding that during a fluid change of just drain and filters should dump most of the 40 quarts (at least 30?)out of the drain plugs not just a couple of gallons. If I can get a confirmation that the driver's side filter can be removed without pulling the driveshaft I will be doing the Transend fluid change out over the Christmas Holiday.