M1079 Transmission Fluid Question

[jkronuch]

I have a 1998 M1079 that I picked up to build into a camper. I am going through the whole truck performing all the needed fluid changes. Now its time for the transmission.

From reading various threads about this, I am thinking of making the switch to ATF, and using Dextron III. I do live in NH, and do plan to put some miles on the truck. Would this be the best way to go, following the procedure of the flush as outlined in other threads? Or should I stick to 15-40? I am not 100% sure whats in there now, seems to have slight red tint, versus just regular 15-40.

The truck seems to shift decent, but I would like to get the fluid and filters changed just so I know its good.

And any decent places to purchase the full service kit with the needed filter and o-rings?

Thank you for the advice.

 

[Awesomeness]

I have ATF in mine, but I don't think you should believe the hype. There are lots of arguments why to change to ATF, but none of them are really a technical/scientific explanation.

The justifications mostly revolve around "I changed it, and it seemed better, or didn't blow up" or "Other similar transmissions run ATF". Both of those are not actually proof of anything, and nobody around here really uses the trucks in extreme enough environments to push the limits of pretty much any fluid you could put in there.

The real question to answer is "Why DIDN'T the Army use ATF?" It doesn't seem likely that it's because they didn't have ATF around or didn't want another fluid... other vehicles use ATF and they have it, plus they can get anything they justify wanting. So there was a specific reason they chose not to, and nobody has offered a good theory.

 

[Floridianson]

I am still running 15w40 in my MTV and not going to get into the oil thing again. I will say I found the man that approved engine oil to be used in the MV and posted his response on the board. He said at the time no transmission had failed because of the engine oil while in service.
Yes ATF will warm up faster and feel better on the shifts. Even my 915A2 still has engine oil and she shifts just fine when the fluid is brought up to temp. Now just for smitts and giggles I started my Allison with ATF in my GMC and the trans. temp. was 53* this morning. I let it idle for ten min. and the fluid temp came up to 68*. With still having engine oil in my MV's I let them have a 30 min. or longer warm up. I do not have a trans. gage in the MTV but if I remember Allison want to see the engine oil in the trans. brought up to close to 100* before putting it to work. Now the 915 has a trans. temp. gage and she always seems to be in the green but I am not pulling what it really could pull. Myself I like the idea of a temp. gage on any automatic.

 

[Mullaney]

I have a 1998 M1079 that I picked up to build into a camper. I am going through the whole truck performing all the needed fluid changes. Now its time for the transmission.

From reading various threads about this, I am thinking of making the switch to ATF, and using Dextron III. I do live in NH, and do plan to put some miles on the truck. Would this be the best way to go, following the procedure of the flush as outlined in other threads? Or should I stick to 15-40? I am not 100% sure whats in there now, seems to have slight red tint, versus just regular 15-40.

The truck seems to shift decent, but I would like to get the fluid and filters changed just so I know its good.

And any decent places to purchase the full service kit with the needed filter and o-rings?

Thank you for the advice.

.
There is another possibility - since you are not sure what is in the transmission: There are companies who specialize in testing motor, transmission, gearbox, and hydraulic oil. You can order a testing kit and know what is in your transmission. Especially if what you have today IS working and has been working. IMO, there is no need to fix something that isn't broken!

Blackstone Laboratories, Inc. in Fort Wayne, Indiana has been used by several members here. You can search for them online, fill out a form and they will send you sample bottles and instructions on how to return them for examination.

To find threads about the process and others experience with their service, search with just the word "blackstone" in the SS search.

Just to make sure it is clearly stated: I am not an employee of that company. I get nothing for the recommendation. Just something I discovered in discussions here and have used in the past. They will evaluate motor oil, transmission oil and gearbox oils. THIS IS NOT A SOLICITATION nor ENDORSEMENT.

 

[Awesomeness]

To rephrase my "don't believe the hype" statement, it doesn't seem like switching to ATF does anything significant. Does it shift a little better, or is that placebo effect? The oil has a higher boiling point, but will you ever reach it? Trivialities! So it ends up largely being a waste of $250+ to do the fluid and filter changeover.

There are a lot of other things I would spend $250 on first. Perhaps rebuild the hydraulic pump, replace the cab latch seals, get new diaphragms for the wheel CTIS valves, get the driveshafts balanced (DEFINITELY!), get a new spare tire, replace some air hoses, have new fuel lines made up, ... the list goes on and on. And then, a couple years down the road, if I'd taken care of all that other stuff (which probably would have failed on its own and forced me to replace it by then), I'd worry about transmission fluid.

I found the man that approved engine oil to be used in the MV and posted his response on the board. He said at the time no transmission had failed because of the engine oil while in service.

I'll have to look for that post.

 

[Third From Texas]

Pull a sample from the sample port under the cab.

You should be able to tell what's in there.

As to what to use, I live in the south where it's hot year-round. My trucks have all run 15w40.

 

[jkronuch]

I was thinking of sending a sample off to Blackstone anyway.
Looks like i will stick with the 15-40. Is there a preferred oil to run? And a good source for the filter kit?

Driveshaft balancing is on the list, was planning on pulling the shafts when servicing the transmission and bringing them to a local shop.

Thank you for the replies!

 

[Moorinsky1]

I was thinking of sending a sample off to Blackstone anyway.
Looks like i will stick with the 15-40. Is there a preferred oil to run? And a good source for the filter kit?

Driveshaft balancing is on the list, was planning on pulling the shafts when servicing the transmission and bringing them to a local shop.

Thank you for the replies!

So I've found everything I've needed for my M1088 at the local napa dealership. There's threads out there with spreadsheets for your filter kit. I'm attaching my screenshot. I hope this helps you out.

FYI: The filter kit runs about 400, but my local napa store got it down to 220ish and some change.
be sure your running that 3070PT transmission too!

 

[Skyhawk13205]

I sourced my filter kit from Allison dealer, it ran about $70. once they have your transmission SN they can lookup your kit number.

my filter kit number was

29558328 - ALLISON TRANSMISSION FILTER KIT, 2" SUMP - Pacific Power Group

Genuine Allison Transmission OEM Part Twin transmission filter kit 2" sump

www.pacificpowergroup.com

Per Allison service letter 10-TR-99, fluid and filter change interval for non tes 295 fluid is 6month to a year depending on severe or general use. Tes 295 fluid is 2 year filter general and severe and 2 to 3 years for fluid dependent on severe or general. Allison service letter notes that oil analysis should be main factor for fluid changes.


My opinion is that the important thing is the oil is changed frequently and properly monitored. To me the tranmission on these trucks are most likely to fail due to heat exchanger failures drive line failures, low fluid and water contaminated fluid.

It is also important to note your temps for cold starting per Allison service manual 15w-40 is operable down to 5F but it requires preheat and warm up to operating temperature before range select.

 

[Moorinsky1]

I sourced my filter kit from Allison dealer, it ran about $70. once they have your transmission SN they can lookup your kit number.

my filter kit number was

29558328 - ALLISON TRANSMISSION FILTER KIT, 2" SUMP - Pacific Power Group

Genuine Allison Transmission OEM Part Twin transmission filter kit 2" sump

www.pacificpowergroup.com

Per Allison service letter 10-TR-99, fluid and filter change interval for non tes 295 fluid is 6month to a year depending on severe or general use. Tes 295 fluid is 2 year filter general and severe and 2 to 3 years for fluid dependent on severe or general. Allison service letter notes that oil analysis should be main factor for fluid changes.


My opinion is that the important thing is the oil is changed frequently and properly monitored. To me the tranmission on these trucks are most likely to fail due to heat exchanger failures drive line failures, low fluid and water contaminated fluid.

It is also important to note your temps for cold starting per Allison service manual 15w-40 is operable down to 5F but it requires preheat and warm up to operating temperature before range select.

That HURTS. Hahaha I'm glad you got a great price. Will definitely be doing this next service.

 

[Awesomeness]

That HURTS. Hahaha I'm glad you got a great price. Will definitely be doing this next service.

Always check the surplus places and eBay too. Those kits are on eBay right now for $25. (You have to use some judgement with NOS stuff so that you don't get old rotten rubber, but for a transmission filter you should be fine.)