Approved Transmission Fluids

[Elijah95]

Hey guys, considering transmission fluid is a fiercely debated topic in the M939 and M35A3 trucks I figured I’d go ahead and start a thread concerning it for us.

All MTVR variants current as of this posting utilize the Allison HD 4070P , a robust 7 speed automatic. Here is a list of Allison Approved fluids you can use in your truck.

Please note where it says “off-highway fluids” and keep in mind that if your truck is going to be used at any point off-road, at speeds below 30 mph for more than 5-10 minutes anytime during the life of the truck you fit the qualification for using these fluids. The military has had excellent success with these transmissions running motor oil.

I do not recommend converting these transmissions to ATF for any reason, you will never get all of the old motor oil out and the cost to rebuild one of these is significant if you cause any damage in the process. The motor oil in this approved list will protect your transmission on and off-road with the small catch that if you’ll warm up your truck for 10 minutes before departure at the start of the day you shouldn’t experience any accelerated wear from being a higher viscosity lubricant.

In summary, one of the best things you could potentially do for your truck after initial inspection and subsequent recovery is to change all fluids, including the transmission oil. Oh and don’t forget the filters





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[sue]

Hey guys, considering transmission fluid is a fiercely debated topic in the M939 and M35A3 trucks I figured I’d go ahead and start a thread concerning it for us.

All MTVR variants current as of this posting utilize the Allison HD 4070P , a robust 7 speed automatic. Here is a list of Allison Approved fluids you can use in your truck.

Please note where it says “off-highway fluids” and keep in mind that if your truck is going to be used at any point off-road, at speeds below 30 mph for more than 5-10 minutes anytime during the life of the truck you fit the qualification for using these fluids. The military has had excellent success with these transmissions running motor oil.

I do not recommend converting these transmissions to ATF for any reason, you will never get all of the old motor oil out and the cost to rebuild one of these is significant if you cause any damage in the process. The motor oil in this approved list will protect your transmission on and off-road with the small catch that if you’ll warm up your truck for 10 minutes before departure at the start of the day you shouldn’t experience any accelerated wear from being a higher viscosity lubricant.

In summary, one of the best things you could potentially do for your truck after initial inspection and subsequent recovery is to change all fluids, including the transmission oil. Oh and don’t forget the filters


The way we read it is, if you “only use it below 30
mph” because spec TES 295 calls out for conventional or synthetic ATF?
Not to argue because we’re looking at a friends truck and he wants to pull it in our shop and change
trans fluid filter etc. was looking at the Allison web
and please correct us if we are wrong.


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[sue]

We were looking at a friends truck and he wants to pull it in our shop and change the trans fluid and filter.
looking at the Allison web site we read it like” if your only going 30 MPH or under”?
Because the TES 295 spec calls out conventional or synthetic ATF.

 

[sue]

We were looking at a friends truck and he wants to pull it in our shop and change the trans fluid and filter.
looking at the Allison web site we read it like” if your only going 30 MPH or under”?
Because the TES 295 spec calls out conventional or synthetic ATF.

 

[sue]

TES
TES 439 is for 5000, 6000 series transmissions

 

[Elijah95]

We were looking at a friends truck and he wants to pull it in our shop and change the trans fluid and filter.
looking at the Allison web site we read it like” if your only going 30 MPH or under”?
Because the TES 295 spec calls out conventional or synthetic ATF.

What I’m saying in short, stick to motor oil 100% of the time. There is zero reason to convert an MTVR to ATF


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[MAdams]

I agree, leave the 15w-40 in there. The trans in the 7 ton runs WAY cooler than a M939 and I think ATF would be fine in the Allison 4000 because it runs so much cooler BUT its a complex trans and you'll never get all the motor oil out if you switched to ATF.

 

[MrMikey4026]

Didn't the spec for 15/40 change in the last few years, I thought the zinc content was greatly reduced?
Possibly this might create issues, as it is not the same as it was 20 years ago.
My Allison expert says use DEXRON3. He said that Transynd was the best choice, but far to expensive.
I doubt if my truck will get more than 1000 miles a year.
I have not serviced mine yet, but he said to drain and over fill, remove cooler return line and let it spew, that would get 90 % of the old stuff out.
The little bit left would not hurt anything.

 

[Elijah95]

MrMikey this is an article taken straight from Allison as of 2-2020.

If it works, why change it?

Our trucks aren’t like the m939 series that frequently had a improperly adjusted and/or rusty throttle cable controlling the transmission line pressure. Many changed to try to obtain smoother shifts, others thought they were improving the transmission, but nonetheless it’s a proven fact that soft shifts are slower shifts, meaning more slippage during the shift equaling advanced wear while quicker-firmer shifts net less wear during the transition giving better service life. Our transmissions are expensive and precise, and reliable per what USMC and Navy mechanic sources are stating.


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[MrMikey4026]

MrMikey this is an article taken straight from Allison as of 2-2020.

If it works, why change it?

Our trucks aren’t like the m939 series that frequently had a improperly adjusted and/or rusty throttle cable controlling the transmission line pressure. Many changed to try to obtain smoother shifts, others thought they were improving the transmission, but nonetheless it’s a proven fact that soft shifts are slower shifts, meaning more slippage during the shift equaling advanced wear while quicker-firmer shifts net less wear during the transition giving better service life. Our transmissions are expensive and precise, and reliable per what USMC and Navy mechanic sources are stating.


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I am good with that,

 

[Coffey1]

The very important reason I would not use DeX in my truck is it has a lower boiling point than oil or 10 weight oil

 

[Elijah95]

Great point Ken, also a point to keep in mind for those that are unaware; transmission fluid starts to turn into carbon at sustained temps above 200, some may resist more than others but you’d be shocked at the temperature observed straight off the torque converter. Heat kills



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[Floridianson]

I can not find the Allison article now but it said 20 minute warm up on transmissions using motor oil. Or when the transmission temperature gage says 100*. With as much engine oil as some of our engines hold I let my engine oil limber up for at least 10 minutes. If I am using the 915A2 that still has engine oil in the transmission then it is closer to 20 minute warm up. Old thread think is was a Deuce A3 with engine oil in transmission OP did not do a good warm up very cold day winter day and took off right away. Yep transmission did not like it and it oops R&R time.

 

[fasttruck]

Anybody read the applicable LO ? I see no reference to it in the above posts. I recall when the 900s first came out around 1988 either DEXTRON or OE 10 was authorized but one or the other: no mixing. Anyone seen changes in the LO ?

 

[Coffey1]

Most of mine had OE 10
The fmtvs have all had motor oil.

 

[Elijah95]

Anybody read the applicable LO ? I see no reference to it in the above posts. I recall when the 900s first came out around 1988 either DEXTRON or OE 10 was authorized but one or the other: no mixing. Anyone seen changes in the LO ?

This is thread is started and concerning the MTVR family of vehicles


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[Coffey1]

Elijah can you tell what's in your truck.
OE 10, motor oil, dex.

 

[Elijah95]

Elijah can you tell what's in your truck.
OE 10, motor oil, dex.

I’m going to pull a sample and send to black stone


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[MAdams]

The TM says 15/40 and I used Delvac which is approved per what Eli posted

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[JonM934]

On my second truck I am thinking of trying a different fuild in the tranny. It is a parts truck so I will not be putting a lot of miles on it but i would be interested to see if it shifts differently.

My truck shifts hard now although it shifts better now that the weather is a little warmer.

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