LMTV M1078 Transmission Fluid Change To ATF Write Up

[Mullaney]

So my 1078 has 17500 ish miles on it, it is 1994 so I'm a little leary of swapping out fluid when the transmission has had oil in it for 30 years / I know it's better for it but I get scared it will screw the transmission up . Thoughts on people doing this with these older trucks

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Me personally, I would leave it like it is. If you are due for a transmission filter change - go for it. Otherwise I would leave it alone. My M1088 and my M1089 run a few thousand miles a year. They both crank up and shift fairly well (smoothly). The M1089 shifts a little "harder" but it weighs in at about 40,000# too, so I am perfectly happy with mine the way they are.

 

[GeneralDisorder]

Thanks for the info, Im curious about the DEX VI is that another viable solution? I ask because the spreadsheet mentions Dex III and Mobile ATF D/M . Just wan to make sure I change it out with the right fluid when I do it

All versions of Dexron are backwards compatible with all previous versions.

The US Army currently uses 15w40 in older trucks (they never flush them to change the fluid type), and both synthetic blend Dex VI and full synthetic Dex VI in newer trucks (all the A1P2 FMTV's use Dex VI). It's up to the unit to decide between full synthetic and synthetic blend - both are available in the system and there's probably not much functional difference between them.

 

[j_boucher]

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Me personally, I would leave it like it is. If you are due for a transmission filter change - go for it. Otherwise I would leave it alone. My M1088 and my M1089 run a few thousand miles a year. They both crank up and shift fairly well (smoothly). The M1089 shifts a little "harder" but it weighs in at about 40,000# too, so I am perfectly happy with mine the way they are.

Normally I would agree but I wanted to travel next January for at least 6 months and now I am working through the truck systems preparing for the trip

 

[j_boucher]

All versions of Dexron are backwards compatible with all previous versions.

The US Army currently uses 15w40 in older trucks (they never flush them to change the fluid type), and both synthetic blend Dex VI and full synthetic Dex VI in newer trucks (all the A1P2 FMTV's use Dex VI). It's up to the unit to decide between full synthetic and synthetic blend - both are available in the system and there's probably not much functional difference between them.

Thanks for the info , greatly appreciated

 

[Mullaney]

Normally I would agree but I wanted to travel next January for at least 6 months and now I am working through the truck systems preparing for the trip

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Well, at that rate you could chew up your transmission and replace it by the time you are ready to make your trip.

 

[Gunny 0369]

Normally I would agree but I wanted to travel next January for at least 6 months and now I am working through the truck systems preparing for the trip

That is why I asked about how many miles you were going to drive, I run mine all over the country.-last year 10,000 miles..
I run Full syn because of that.
A parade truck,
Eh, change filters and yippikyaa.

 

[hike]

Thanks for the info, Im curious about the DEX VI is that another viable solution? I ask because the spreadsheet mentions Dex III and Mobile ATF D/M . Just wan to make sure I change it out with the right fluid when I do it

@GeneralDisorder mentions DEX VI in item2 in post 98 above—

 

[MatthewWBailey]

Doing this conversion. Filters done today. Just need to go buy 60quarts of Dex6 somewhere.

 

[MatthewWBailey]

60 quarts. Thankfully they're only available in quart-sized containers or 55gal drums. Spec says synthetic

https://www.napaonline.com/en/p/NOL75208

 

[MatthewWBailey]

Another question for you guys but probably low level. Im refilling from a full drain of both case and trans. 9+ gallons came out from servicing the filters. The original post references "refilling 5 gals" and then running the engine first. So do I put all 39 quarts in first or do I have to run it first before I can put all the ATF in there? I have 5 gallons in there now. I noticed that the transfer case doesn't simply gravity feed from the trans. So I'm just nervous about how to do it.

 

[GeneralDisorder]

It likely won't take it all. You'll have to run it briefly to pump it through the cooler, and filters, etc before it will take the rest of the fluid.

 

[Skyhawk13205]

60 quarts. Thankfully they're only available in quart-sized containers or 55gal drums. Spec says synthetic

https://www.napaonline.com/en/p/NOL75208

View attachment 928571

Quarts bottles are not so bad, easy to carry up and fill the spout. At least it is not like the old days where you had to bring a dull can opener and pop open every can. I had to fill a 10 gallon hydraulic tank with skydrol 1 quart steel cans via a hand pump.

when I filled my transmission from empty, I just filled till it hit the cold mark, started the truck, while idling filled again till it reached the cold mark, then cycled from N to R to D back to N then checked it again and filled a bit till cold mark. It prob took me about 2-3 drive cycles of filling till the level was in the correct hot range.

 

[MatthewWBailey]

Quarts bottles are not so bad, easy to carry up and fill the spout. At least it is not like the old days where you had to bring a dull can opener and pop open every can. I had to fill a 10 gallon hydraulic tank with skydrol 1 quart steel cans via a hand pump.

when I filled my transmission from empty, I just filled till it hit the cold mark, started the truck, while idling filled again till it reached the cold mark, then cycled from N to R to D back to N then checked it again and filled a bit till cold mark. It prob took me about 2-3 drive cycles of filling till the level was in the correct hot range.

View attachment 928721View attachment 928723View attachment 928722

My dipstick only had the hot level marks. But since the driveshafts are out being balanced, I can run the trans easily enough.

 

[MatthewWBailey]

It likely won't take it all. You'll have to run it briefly to pump it through the cooler, and filters, etc before it will take the rest of the fluid.

I had the "to cooler" flex line open and stuffed in a 5 gal bucket during todays 1st run. Only took 90 seconds to flush 5 gallons lol. Coming out full red now. Thanks for the direction on that technique. That was really easy.

 

[MatthewWBailey]

First test drive. Shifting is noticeably smoother especially during the exhaust brake downshift as well as 2-3 up shift. I was a couple quarts low after the drive.

 

[aw113sgte]

I had the "to cooler" flex line open and stuffed in a 5 gal bucket during todays 1st run. Only took 90 seconds to flush 5 gallons lol. Coming out full red now. Thanks for the direction on that technique. That was really easy.
View attachment 928922

Link to technique? Does that include shifting through gears? Better option than drain plugs?

 

[MatthewWBailey]

Link to technique? Does that include shifting through gears? Better option than drain plugs?

I don't think it's posted. He just told me to pump it into a bucket using the "to cooler line" until it came out full red. I actually pumped out 5.5 gallons bc I was busy watching the oil psi gauge. It was in drive during this bc my driveshafts were off, so it was spinning in 2. As a flush it makes more sense to me than the drain plugs bc the flow was substantial, based on the video time it was about 3gal/min. I can't see how any old oil would not go thru the pump.

 

[aw113sgte]

I don't think it's posted. He just told me to pump it into a bucket using the "to cooler line" until it came out full red. I actually pumped out 5.5 gallons bc I was busy watching the oil psi gauge. It was in drive during this bc my driveshafts were off, so it was spinning in 2. As a flush it makes more sense to me than the drain plugs bc the flow was substantial, based on the video time it was about 3gal/min. I can't see how any old oil would not go thru the pump.

I've heard people doing this and running till it sputters(runs out of fluid). Then refill and run till you see fresh, then fill to appropriate level.

 

[GeneralDisorder]

I've heard people doing this and running till it sputters(runs out of fluid). Then refill and run till you see fresh, then fill to appropriate level.

Yep. I pulled the line off the cooler and I ran about 4-5 gallons through it. Filled the pan twice IIRC and basically ran it till the pump emptied the pan and then shut it down. After installing the new filters and draining the pan.

 

[aw113sgte]

Yep. I pulled the line off the cooler and I ran about 4-5 gallons through it. Filled the pan twice IIRC and basically ran it till the pump emptied the pan and then shut it down. After installing the new filters and draining the pan.

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.