So getting ready to leave on a trip towing ~10k lbs about 900 miles round trip. It's time to change my transmission fluid. I have 255,000 miles on my truck now. Had the fluid changed twice before. Once by the stealership (probably around 2004) and once by an after market shop. Plan on doing it myself this time. Question is, what kind of fluid to use? I assume I have Dex III or maybe Dex VI in it now. Been reading and lots of folks saying use TranSynd??? So what do you guys think? What should I use? Also how much. Drain the pan and change the spin on filter - how much fluid will that take?

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Nobody knows? Went thru the owners manual and found out it's Dex III but still haven't got a clue how much.

 

There is no point to change to a synthetic because there will still be a LOT of oli fluid left in the trans. If the fluid is still red and smells good yet, I'd just spin a filter on add what you lost and roll on.

 

Well I called Allison today to get their opinion.

They definitely recommend the TES-295. Not Dexron III and not Dexron VI.

TES-295 would be products like Castrol TranSynd, Mobil 1 Delvac ATF. He said John Deere, International and few others also make ATF that meets the TES-295 standard.

Also there are two models out there. The deep pan and shallow pan. Deep pan is 3" deep at shallowest part of the pan.

Deep pan takes 10.4 quarts to refill after a pan drain.

Shallow pan requires 7.5 quarts.