LMTV M1078 Transmission Fluid Change To ATF Write Up

[MatthewWBailey]

I wonder how well it would circulate through the secondary cooler on my mtv. There is that piece people were thinking was a bypass. Guessing I should drain from the return before it goes back into the tranny.

Just an FYI, I had pulled my cooler to get to the oil pump/pan. So it was draining for a few weeks in a bucket. But without pulling it, I'd think doing what you're saying is effective at flushing the cooler itself.

 

[GeneralDisorder]

I pulled the *return* hose and let the cooler nipple dump into a bucket so when I did it the cooler also got flushed.

If you have an MTV with the secondary cooler you should flush that separately and also note those have thermostatic valves so you have to work around that in the process.

Might consider something like this - virtually all the replacement remanufactured transmission we buy at my shop come with a can:

KOOLER KLEEN Transmission Cooler & Line Flush with NEW 2-in-1 Fitting - Lubegard

www.lubegard.com

 

[MatthewWBailey]

This might be a silly question but do the dipstick fill marks apply to ATF? Or just the old 10w-30 motor oil? I filled mine to the cold fill mark, but today I saw a big ATF leak after a hot test. It's coming out of the breather rather liberally, or at least it was. It's all wet up there. Easy to see. I'm thinking I overfilled it but now the dipstick level is at the Low mark and the fluid is hot. Wouldn't the dipstick marks need to change for the different fluid type? Just guessing

 

[Mullaney]

This might be a silly question but do the dipstick fill marks apply to ATF? Or just the old 10w-30 motor oil? I filled mine to the cold fill mark, but today I saw a big ATF leak after a hot test. It's coming out of the breather rather liberally, or at least it was. It's all wet up there. Easy to see. I'm thinking I overfilled it but now the dipstick level is at the Low mark and the fluid is hot. Wouldn't the dipstick marks need to change for the different fluid type? Just guessing

.
I don't think so... The level of the oil is (should be) unaffected by the type of oil.

 

[Ronmar]

yea, silly question...

 

[GeneralDisorder]

Yeah no change to the dipstick required in my experience. I'm sure the difference in coefficient of expansion between the two fluids is measurable but it's not significant enough to see with the naked eye would be my guess.

 

[MatthewWBailey]

yea, silly question...

Show off

 

[Ronmar]

Show off

Been there, Done that, Qualified to make the call...

 

[Piatheem]

Ok, it has been almost 10 years since this great thread was started. Thank you @Overdrive for an excellent writeup. Just want to confirm that following is still true in 2025 for A1 trucks:
1) Three times flush is still the best way to replace HDO with ATF.
2) Looks like TES 295 was replaced with TES 668. Is CASTROL TRANSYND 668 ALLISON TES FULL SYNTHETIC AUTOMATIC TRANSMISSION FLUID the best option to date?
3) Is best filter kit PN: 29540493? I prefer original parts, unless there is a better kit.