transmission oil change for HEMTT

[Floridianson]

Since you've mentioned engine oil at least twice, make sure that the multi-grade 15-40W is out of the engine; use only straight-grade SAE40 (or 30W in cold weather) LOW-ASH, DETERGENT-TYPE oil in your 2-stroke Detroit. Otherwise you'll score your liners, among other things. Shell Rotella makes a nice compatible oil that is widely available.

Yep very important.
Also one would think how was the machine to be used in the case of the transmission. Going down a highway at speed plenty of air flow and cooler transmission. Mud pits and mountain climbing would be low ground speed, high rpm and little air flow. Good luck with what happens.

 

[2deuce]

For the engine I changed it to straight 40wt Delo 100 which is specially formulated for Detroit diesels. The truck hasn't been driven off road since it was rebuilt. It is very clean on the underside and I plan only on road use.
I somehow missed Swamp Donkey's post until now. He hit it on the head when he said you have to feel good with what your running, that is what it ultimately comes down too. If you have strong feelings with what you are running you may get upset trying to keep that good feeling by reading here, I hope not. Burning the oil to find out what is in there is also something I will do, and didn't think of before. Wear patterns are something to weigh in my decision, but heat is what I see as a bigger concern and if TES295 can lower heat generated that would be a consideration depending on amount. I think I read somewhere that a drop in temps were noted. I hope others who have done the switch will provide their results.

 

[JDToumanian]

Jon, did you change your oil more than once? If not the percentage of old to new is still high since only about half drains each time you change it.

No, just the one change when I got the truck last year. I want to do it again and I have the oil, but not the time at the moment...

Jon

 

[Gunzy]

I run Delo 100 40wt in my M985 engine and will stay with what is in the trans from the military for 2 reasons, the trans is wear conditioned to the 15w40 or 10 wt that is in there and the engine oil handles higher temps better. I have seen 220 on trans on paved roads running hills. I don't 100% trust my temp gauges and that is another Item I need to look at in the future.

 

[2deuce]

Gunzy, is your M985 engine any different than a M977 engine? also if your transmission fluid is low, what will you add? One thing I don't understand is the wear patterns or wear conditioning that is purported to be going on with different oils. It would seem to me at least from a logical standpoint that the transmission is going to wear in the same places no matter which oil is used, but the amount of wear accelerates as temps rise, as oil loses it's properties as it gets older, or gets contaminated. An oil that requires less frequent changes would seem to suggest that it retains it's properties better. An oil that runs cooler suggests less friction, or has better heat dissipation, or both, and the wear that is going on has to be lessened. Now I can see where a heavier oil would have different properties and abilities at different temperatures than an oil that is the same but only a lighter weight, but a totally new oil like TES295 compared to the best option oil available before it is harder to compare, except where heat is generated. If heat is less it should be considered an improvement, if it is claimed to lubricate better at higher temperatures that is something that we would have to trust from the builder of the transmission who recommends.

The way I'm trying to decide whether to switch or not is hinged on what Allison approves. TES295 is what is approved today. !5/40wt motor oil was approved long ago, because it was the best option back then. The politics that went on between the military and allison will never be known and always debated. Back when detergent oil came out it was not a good option if your engine had run a long time on non-detergent. The tough decision is whether the transmission will like the change, like my cat when I changed his litter type and decided not to use it.
I would say it is likely that the way I drive my truck is going to be different than the prior driver. That in itself would create different demands on the transmission and affect wear and tear, and should be a big factor in transmission life. When everything is added up I feel that transmission longevity should be improved with an improved oil, if everything remains the same. How much is the improvement and is it worth it if there are risks. That is where we will make different decisions.

 

[2deuce]

JDToumanian, by changing it one time that left probably 10 to 15 qt of original oil in the transmission. Did you notice any change in transmission temperature? Have you put many miles on it since the change and did you notice any other characteristics that changed?

Thanks

 

[Gunzy]

I have a simple philosophy about my MVs, if it isn't broke don't fix it. Now, if I lose a trans and have it rebuilt I may change over to a "Trans " fluid. But until then, if ever, I will run what came in it as I don't see the expense of changing it to be any advantage. I have discussed this with a couple trans builders and they tell me to stay with what is in it or face a possible failure. But, in the end it is your rig and you can do what you feel is best for you.

 

[2deuce]

Gunzy, I can relate to your philosophy for sure. Did you change your transmission fluid when you got your truck? I just mean a change not a switch. I think the military lists a change of fluid every year. I will have to double check that. Once that cost factor is added in, then the initial cost of TES295 becomes a savings because it isn't required to be changed as often. The cost of oil isn't really a factor for me. It is the cost of a new transmission. And the down time. If the transmission fails it could have a tree growing up through the frame before I get to it.

I hope more guys that have done this switch let us know their feedback.

 

[JDToumanian]

JDToumanian, by changing it one time that left probably 10 to 15 qt of original oil in the transmission. Did you notice any change in transmission temperature? Have you put many miles on it since the change and did you notice any other characteristics that changed?

I picked up my truck in Louisiana and drove it home to CA, over 1,700 miles. I changed all the fluids there in LA, and I only drove the truck for a 1/2 hour or so to warm it up beforehand, so I have no real basis to compare to. In general, it runs quite cool, the only time I see it rise is pulling long grades, like my local Cajon Pass, at which point I find the engine putting out near max horsepower and starting to get hot as well (both are related I'm sure, since the trans cooler is in the bottom of the radiator). I don't like things to run hot, so I quickly learned that when the engine is near max HP, it's time to back off and downshift. I pull Cajon Pass at 40 mph in the truck lane, it's not worth blowing head gaskets, liner seals, or transmission just to get up the hill at 55. My intention was to change the trans oil again when I got home from the recovery trip, but I moved last summer and have just been too busy renovating my 'new' 60-year-old house.

 

[2deuce]

One thing that has been pointed out to me is the clutch plates are saturated with 15/40. How does that work with a switch to TES295? That seems to be a major concern. That leads to the next question. How do the 2 oils mix? How well do they mix in that small area between the plates?
I think that the life of the transmission will be impacted with 15/40, but there is also a risk with a switch. That risk is probably greatest a short time after the switch. As you can see I haven't made up my mind yet, and still sitting on the fence.

 

[JDToumanian]

I hear ya... I knew I wanted to switch but I was worried about making the transition as you are. That's why I bought the new spare transmission in the can. I'd hate to push my advice and have it fail on you.

Have you read the factory Allison operator's manual? That's another factor that heavily influenced my decision to switch. In my copy of Allison's OM1334EN dated Feb. 2001, it shows TES295, DEXRON III, and C-4 as approved fluids, yet does not recommend DEXRON III or C-4 for any application... GONE is the wording allowing C-4 for "off highway" or "severe service". Instead, it says, "TranSynd is a fully synthetic automatic transmission fluid that meets new Allison specifications for Severe Duty and Extended Drain Interval."

As for mixtures of TES295 and either C-4 or DEXRON III, I don't think it's too much of an issue. The manual even has an oil change interval chart for mixtures, and defines "mixture" as "... the quantity of fluid remaining in the transmission after a standard fluid change combined with the quantity of TranSynd that is required to fill the transmission to the proper level." Exactly our scenario.

Regards,
Jon

 

[2deuce]

I'm going to go back and thank everyone that has tried to help me with this decision. One good thing is I've learned quite a bit about oil, about approved oil, and it surprises me that these ratings and specs change, but what is printed on the label may not, making the value of these ratings very questionable, even meaningless.
I'm going to go with my gut feeling on this issue. Something Swamp Donkey alluded to when he said you have to feel good about what your running. I just don't feel good with the military's decision to run 15/40 in my Detroit Diesel. I don't feel that their objectives match mine. I don't trust that the transmission fluid they chose was the best they could do for their transmissions either. They had other reasons for running what they do. What contributes to my gut feeling without knowing much about oil is that motor oil is for engines and atf is for automatic transmissions. The best atf for our transmissions would seem to be what the manufacturer approves. Why wouldn't they approve the best choice. I'm not trying to persuade anyone else to switch, I'm just trying to explain why I intend to tomorrow morning. I drained about 10 gallons out tonight.

One last thought... If I was to keep the same oil in my transmission, I had made up my mind to put in fresh oil and to keep it fresh. I already have what I drained out tonight in the tank of my Deuce.

Thanks again

 

[Elideclan2]

I have done both. I have drained the transmission and replaced only what came out with transynd on my m983.
I have also just topped off the fluid level with oil in my m977.
Both ran the same. No appreciable difference. Last fall I sold the m983 and it drove from Massachusetts
to south Florida with no issues ( other than kidney failure)

 

[2deuce]

Update... We(my son and I) did the drain and fill. It was a little more than 8 gallons that came out. We added 8 gallons to get in the cold range. The transmission had an annoying habit of shifting up to the next gear then immediately shifting back down before shifting back up. It did this between 1st and 2nd and also between 2nd and 3rd, not between 3rd and 4th where it shifts normally. The transmission continues to do this after the change. We haven't done the 2nd change yet thinking that if this shifting abnormality is something that requires another fluid drain we would waste fluid by finishing the switch over now.

Anybody have their HEMTT shift like this? We have a 300 mile trip planned next Thursday. The truck has not been used much in the last few years so maybe a trip like this is what it needs. I hope somebody has some experience with this.

Thanks

 

[Elideclan2]

When I first got my truck from gov planet it slipped something awe full. I actually bought another transmission it was so bad.
Upon purchasing another trans the trans in the truck started working!
Driving them sometimes does help. I find it shifts better when the transmission is at running temp ~180ish~

 

[2deuce]

I'm hoping that a good long drive will help. This transmission is not slipping in the sense that the engine speed increases but the road speed does not in the same gear. I have had turbo 400's do that at the end of their life, before rebuild. This one gives the extra shift up and down and locks in when it does, it effectively jerks us around. If I let up on the throttle at the shift point it doesn't shift back down and stays in the gear and I then can accelerate. It's like using the throttle as a clutch. My son thinks that I'm trying to accelerate too fast,because the engine in the 2 stroke detroit sounds like it's really reving, but I'm only about half throttle. Possibly if I were to accelerate harder it wouldn't do this but I think it might be worse. That's the way it feels. I've thought about buying another transmission too.

 

[2deuce]

The other thing is the truck has less than 7500 miles on it, which I believe is from the last rebuild. It had new batteries put in that have a charged on date of sept 2010. This makes me think that date may have been the rebuild date. I know the truck was not run or moved for a year at least when I bought it. I'm the 1st civvy owner.

 

[dk8019]

Mine shifts like this some times. I have a spare transmission in a can just in case too!

I've got another drain/fill cycle coming this fall as well. Maybe it will improve. It does act far better when it warms up.

 

[Floridianson]

Possibly if I were to accelerate harder it wouldn't do this but I think it might be worse. That's the way it feels. I've thought about buying another transmission too.

Well when the transmission fluid is up to temps try a full peddle run up. The motor has a governor so you won't hurt that and that Allison will handle just about anything you can throw at it. I don't know what transmission is in there so I ask you is it the computer or transmission governor that tells it when to shift.
Mine is the HT740 governor controlled and it drives so much nicer if I control the rpm/shift using the shifter and I run it up to 1800 / 1900 rpm for the shift. Governor is 2100 rpm. Mine is a series 60 four stroke not a two stroke but I bet if you wind it out more it will feel better. Also my lockup comes in second gear so I don't let off the throttle or try and force a shift just keep on adding throttle.

To add to this post if the Allison spec is correct then your trans could go from 1st unlock to first lockup then 2nd unlocked then to 2nd lockup. Do you think that is what you are feeling? Maybe you letting up it is unlocking and locking. I still feel you need to lay into it and maybe even see how it preforms when you manual shift it. You should feel the shift lock up in first and second by manual shifting it and will be noticed because you are not shifting the shifter but holding the next gear shift back with the shifter but not the lock up. Again don't be afraid to wind that motor up to maybe 300 rpm before the governor when manual shifting for a test run. The thing I found on mine if I half throttle it shifts different as it should than full throttle. When I am driving in town I sometimes lock it in 2nd or 3rd because of stop and go to stop any up shifting and that also keeps the rpm higher if I need engine braking. These are heavy machines and sometimes I find the trans. want to shift to a higher gear but the rpm drop just a bit and the trans. then down shifts if I don't keep on the throttle and feels like it is lugging. Then it down shifts again and no more lugging. I like to get the machine up to speed so as said I can lock in a lower gear to keep the rpm up in town or on the open road I don't let up on the throttle till its up to highway speed. These trucks when everything is working right do not drive or act like a pickup truck.

 

[bigred350]

I dont know if my tranny is 10wt or 15/40 but from the dip stick its definitely oil. so my question is will i hurt anything by adding 10wt to 15/40 or vise versa?