LMTV M1078 Transmission Fluid Change To ATF Write Up

[Awesomeness]

It's in my Common Issues document, here in my signature.

 

[Asymair95]

I believe this is the relearn procedure.

 

[astacey1403]

Got a quick question for you guys thought this would be the correct thread for it.

How can you tell if a truck has already been switched to trans fluid? And is the original fluid in these really 15-40? I got my 98 M1079 running the other day and have been driving it around town. It is about 19f out this morning and the trans fluid is not on the dipstick at the moment. Before startup I checked trans fluid level and was low on the cold mark however the fluid was red in color witch I assumed was and ATF of some type.

At the moment the fluid is low enough that the truck will not go into drive or revers and I will need to add some fluid. Should I Just stick with 15-40 for now?

 

[Awesomeness]

Got a quick question for you guys thought this would be the correct thread for it.

How can you tell if a truck has already been switched to trans fluid? And is the original fluid in these really 15-40? I got my 98 M1079 running the other day and have been driving it around town. It is about 19f out this morning and the trans fluid is not on the dipstick at the moment. Before startup I checked trans fluid level and was low on the cold mark however the fluid was red in color witch I assumed was and ATF of some type.

At the moment the fluid is low enough that the truck will not go into drive or revers and I will need to add some fluid. Should I Just stick with 15-40 for now?

ATF is red, and oil is clear. The original fluid is 15W-40.

EDIT: Checked the TM 9-2320-365-10, F-3, and it's 15W-40 above 40°F, and straight SAE-10 from 40°F down to -15°F.

 

[astacey1403]

ATF is red, and oil is clear. The original fluid is SAE 40 (straight weight, not 15W-40).

These are the fluids that are available at the local Big R. I'm thinking I may just get the trans fluid.

 

[Awesomeness]

These are the fluids that are available at the local Big R. I'm thinking I may just get the trans fluid.

I was mistaken before, and corrected my post. 15W-40 will be what you want. I've found good deals on synthetic 15W-40 at Sam's Club, and Costco / BJ's may have something similar.

But if your fluid was red, don't you want the ATF?

 

[Mullaney]

Got a quick question for you guys thought this would be the correct thread for it.

How can you tell if a truck has already been switched to trans fluid? And is the original fluid in these really 15-40? I got my 98 M1079 running the other day and have been driving it around town. It is about 19f out this morning and the trans fluid is not on the dipstick at the moment. Before startup I checked trans fluid level and was low on the cold mark however the fluid was red in color witch I assumed was and ATF of some type.

At the moment the fluid is low enough that the truck will not go into drive or revers and I will need to add some fluid. Should I Just stick with 15-40 for now?

.
Another thing that you can do with these trucks is to have the oil analyzed. There are lots of companies that do that work - and it isn't as expensive as you might expect. Blackstone Laboratories, Inc. in Fort Wayne, Indiana is one place to look at. They will send you a sample bottle and instructions as well as a return mailer pre-addressed for analysis. Their oil inspection can tell you if there is clutch debris in the oil and what condition the oil is in as well.

Was your truck bought from an individual - and not direct from the military? Like @Awesomeness suggested, red transmission oil is most likely ATF. Even more likely the motorpool mechanics didn't put ATF into your transmission. Maybe in a Guard unit, but still not very likely.

There are two types of red ATF too.
Type F and Dextron.
You need to be sure you use the right stuff... Oil based or Vegetable

10wt motor oil is the right thickness AND you shouldn't mix one with the other.

 

[Third From Texas]

Yep IMO, the only way to be certain is to pull a sample from the sample port that can be tested to confirm if there is the slightest question.

It's not expensive (like $10).

 

[Mavcaster]

If sticking with motor oil, can a synthetic oil such as Rotella T6 be used in the tranny without the need for a flush?

 

[Awesomeness]

If sticking with motor oil, can a synthetic oil such as Rotella T6 be used in the tranny without the need for a flush?

Yep

 

[Mavcaster]

That’s probably what I’ll stick with then to keep things simple and considering my truck already has 54K on it…not sure the juice is worth the squeeze at this point.

 

[o.oj]

So, just to confirm, beside the nuance of sticking with motor oil or going ATF....
I'm not making any colossal mistake by using Rotella T6 15W 40 in my engine and transmission?

 

[GeneralDisorder]

So, just to confirm, beside the nuance of sticking with motor oil or going ATF....
I'm not making any colossal mistake by using Rotella T6 15W 40 in my engine and transmission?

Assuming it had 15w40 in the transmission already, then no. That should work fine. The military did switch to using Dex VI (synthetic is an option) in the 3700SP on the newer A1P2 trucks. FWIW. I switched mine over to mil spec synthetic Dex VI along with using about 3-4 additional gallons to flush it along with new filters and have nothing to report other than it's as happy as ever and the fluid looks new still several thousand miles later.

I don't know but I suspect that the C6 thrust bearing issue on these transmissions might be somewhat mitigated by using ATF vs motor oil. But that's speculation. ECO hubs to drop the transmission speed by half can't hurt either. It's a concern that's bitten more than one owner.

 

[aw113sgte]

I don't know but I suspect that the C6 thrust bearing issue on these transmissions might be somewhat mitigated by using ATF vs motor oil. But that's speculation. ECO hubs to drop the transmission speed by half can't hurt either. It's a concern that's bitten more than one owner.

Having done this, it's really easy to update that bearing on the newer trucks without the cross member on the upper frame rail (might depend on the truck designation too). Price for the plastic bearing is ridiculous though.

 

[GeneralDisorder]

Having done this, it's really easy to update that bearing on the newer trucks without the cross member on the upper frame rail (might depend on the truck designation too). Price for the plastic bearing is ridiculous though.

It looks fairly impossible on my M1079 without cutting out the frame rail and welding it back in. I'll look again though since that would be an excellent idea to do so.

 

[j_boucher]

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

 

[Gunny 0369]

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

How many miles do you travel a year in your truck?
When is the last time you changed your filters and oil in the transmission?
Do you have any shift problems now?

I have done both, change the filters and oil out in mine, which is also a 95, and it shifted so much better.
I ended up going all synthetic because I put a new transmission in mine, annd the system was broken down and properly flushed- and of course, it also shifts very smoothly, up and down.

 

[GeneralDisorder]

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

As a shop owner, professional master technician, Motorpool veteran, and LMTV owner. This is my perspective.

1. In general, most people forget about transmission maintenance unless something prompts them to consider it. This is very often some sort of "behavioral" problem they perceive (correctly or incorrectly) as a transmission problem. Their first inclination is to change the fluid and since they feel bad for neglecting it they want to treat baby to a nice steak dinner and they buy whatever flavor new/different/synthetic/additive, etc for the occasion - in the case of a transmission that's already got problems this very often makes the situation worse as the only thing making the clutches not slip worse was the thick and gritty fluid with lots of suspended solids from the worn clutch plates. Clean fluid washes all that away and opens up the clearances even more causing rapid decline in operational performance. The unsophisticated owner then blames the new fluid change for the failure. When in reality the type of fluid had nothing to do with the rapid failure as any new fluid - right or wrong - would have had the same effect and the transmission was already done for before they started.

2. You hear much more loudly about the failures than you do the successes. I changed over from 15w40 to synthetic Dex VI for no other reason than the original fluid was 15 years old - looked fine and drove fine. And I have zero problems before or after.

3. The US Army and Allison recommend ATF. 15w40 is only "acceptable" and remember the expected lifespan of the truck in military service is about 35k miles. Many get far less than this but this is the projected service life. You could probably run just about anything from a 10 weight hydraulic tractor oil to 20w50 motor oil in them for that long if you are assuming a properly built brand new transmission and have no issues. Anything that doesn't attack the seals or the clutches is going to work for that short of a life expectancy. Is it ideal? No probably not which is why it's "acceptable".

4. All of the MD3070 and 3700SP transmission found in the trucks available to the civilian market have the C6 thrust bearing lubrication issue. Allison eventually solved this by essentially removing the problem - they replaced that bearing with a plastic self-lubricating thrust spacer. But that happened after all the trucks in civilian hands were produced so in all likelihood (unless the transmission has been replaced, etc) this potential failure lurks in all of our trucks. ATF is about a 10 weight and flows better at lower temperatures meaning it's going to get up to that area faster and easier during warm-up. Synthetic ATF has even better low temperature flow characteristics. This was a major factor in my decision to go away from the 15w40. The ATF has a larger operational temperature envelope in any of the places I'm likely to be with my truck (IE not the Middle East, etc). I'm much more likely to go an play in the snow than a 130 degree desert. Low temp lubrication is undoubtedly improved with ATF and preventing that C6 bearing from being a problem is at the top of my list for things I want my transmission fluid to be doing.

Change your fluid. Put some proper synthetic ATF in there and flush it well - don't skimp on flushing volume - I used about 3-4 gallons of new synthetic fluid to flush out the system.

 

[Gunny 0369]

As a shop owner, professional master technician, Motorpool veteran, and LMTV owner. This is my perspective.

1. In general, most people forget about transmission maintenance unless something prompts them to consider it. This is very often some sort of "behavioral" problem they perceive (correctly or incorrectly) as a transmission problem. Their first inclination is to change the fluid and since they feel bad for neglecting it they want to treat baby to a nice steak dinner and they buy whatever flavor new/different/synthetic/additive, etc for the occasion - in the case of a transmission that's already got problems this very often makes the situation worse as the only thing making the clutches not slip worse was the thick and gritty fluid with lots of suspended solids from the worn clutch plates. Clean fluid washes all that away and opens up the clearances even more causing rapid decline in operational performance. The unsophisticated owner then blames the new fluid change for the failure. When in reality the type of fluid had nothing to do with the rapid failure as any new fluid - right or wrong - would have had the same effect and the transmission was already done for before they started.

2. You hear much more loudly about the failures than you do the successes. I changed over from 15w40 to synthetic Dex VI for no other reason than the original fluid was 15 years old - looked fine and drove fine. And I have zero problems before or after.

3. The US Army and Allison recommend ATF. 15w40 is only "acceptable" and remember the expected lifespan of the truck in military service is about 35k miles. Many get far less than this but this is the projected service life. You could probably run just about anything from a 10 weight hydraulic tractor oil to 20w50 motor oil in them for that long if you are assuming a properly built brand new transmission and have no issues. Anything that doesn't attack the seals or the clutches is going to work for that short of a life expectancy. Is it ideal? No probably not which is why it's "acceptable".

Change your fluid. Put some proper synthetic ATF in there and flush it well - don't skimp on flushing volume - I used about 3-4 gallons of new synthetic fluid to flush out the system.

Spot on

 

[j_boucher]

As a shop owner, professional master technician, Motorpool veteran, and LMTV owner. This is my perspective.

1. In general, most people forget about transmission maintenance unless something prompts them to consider it. This is very often some sort of "behavioral" problem they perceive (correctly or incorrectly) as a transmission problem. Their first inclination is to change the fluid and since they feel bad for neglecting it they want to treat baby to a nice steak dinner and they buy whatever flavor new/different/synthetic/additive, etc for the occasion - in the case of a transmission that's already got problems this very often makes the situation worse as the only thing making the clutches not slip worse was the thick and gritty fluid with lots of suspended solids from the worn clutch plates. Clean fluid washes all that away and opens up the clearances even more causing rapid decline in operational performance. The unsophisticated owner then blames the new fluid change for the failure. When in reality the type of fluid had nothing to do with the rapid failure as any new fluid - right or wrong - would have had the same effect and the transmission was already done for before they started.

2. You hear much more loudly about the failures than you do the successes. I changed over from 15w40 to synthetic Dex VI for no other reason than the original fluid was 15 years old - looked fine and drove fine. And I have zero problems before or after.

3. The US Army and Allison recommend ATF. 15w40 is only "acceptable" and remember the expected lifespan of the truck in military service is about 35k miles. Many get far less than this but this is the projected service life. You could probably run just about anything from a 10 weight hydraulic tractor oil to 20w50 motor oil in them for that long if you are assuming a properly built brand new transmission and have no issues. Anything that doesn't attack the seals or the clutches is going to work for that short of a life expectancy. Is it ideal? No probably not which is why it's "acceptable".

4. All of the MD3070 and 3700SP transmission found in the trucks available to the civilian market have the C6 thrust bearing lubrication issue. Allison eventually solved this by essentially removing the problem - they replaced that bearing with a plastic self-lubricating thrust spacer. But that happened after all the trucks in civilian hands were produced so in all likelihood (unless the transmission has been replaced, etc) this potential failure lurks in all of our trucks. ATF is about a 10 weight and flows better at lower temperatures meaning it's going to get up to that area faster and easier during warm-up. Synthetic ATF has even better low temperature flow characteristics. This was a major factor in my decision to go away from the 15w40. The ATF has a larger operational temperature envelope in any of the places I'm likely to be with my truck (IE not the Middle East, etc). I'm much more likely to go an play in the snow than a 130 degree desert. Low temp lubrication is undoubtedly improved with ATF and preventing that C6 bearing from being a problem is at the top of my list for things I want my transmission fluid to be doing.

Change your fluid. Put some proper synthetic ATF in there and flush it well - don't skimp on flushing volume - I used about 3-4 gallons of new synthetic fluid to flush out the system.

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