LMTV Transmission Issues

[Waltjg]

Anybody have any experience with this issue: I drained the transmission on my LMTV of the motor oil the Army was using, filled with Dex-III and went on a spin to flush the fluid thru the system. Then I planned to drained again, change filters and refill with Dex-III. (I have not yet done the second drain and filter change; got held up on an air brake issue--see my other post about that if interested.) On my flush-run the truck would not drive in any gear but 4th. It reverses fine, but when I hit drive it pops into reverse, shows 7 momentarily on range selection screen, then jumps hard into 4th and won't shift again. I have to shut the truck down completely and restart to get it back in neutral.

 

[swbradley1]

Not to beat a dead horse but have you looked at the manual and the huge troubleshooting section for the transmission?

 

[Waltjg]

Ya, thanks. The manual just gives a big list of fault codes, but how do I get it to give me a fault code???

 

[Suprman]

What dextron 3 did you use? If it's not the quality allison approved stuff I wouldn't use it.

 

[Waltjg]

76 Super ATF: http://petroleumservicecompany.com/76-super-atf.html

 

[Suprman]

I didn't see it on the Allison approved list. If it worked before with the military fluid and it won't work now that you changed the fluid, go back to the old fluid type.

 

[MaiNiaK]

Here is a link that has all the info you should need. Error codes, fluid type and a bunch more info.
http://www.utxchange.com/pdfs/MechanicsTips/MT2923EN.pdf

This is what Allison recommends for DexIII fluid.

Here is a good example of fluid, DexIII (C4)
http://www.oreillyauto.com/site/c/d...rcon!s!dexron_-1_4518&keyword=mercon!s!dexron


Page 18 of above pdf, starts the fluid and filter change procedure.


Good luck

 

[Waltjg]

Awesome. Thank you MaiNiaK!

 

[Keith Knight]

My M1078A1 2003yr had all the fluids drained when I picked it up from GovPlanet. So I filled my Transmission with DexIII and it ran well until my first 100 mile round trip and 1/4 mile from home it shifted into neutral and rolling to a stop. Turning it off and back on a few times I was able to get it home and it never ran properly again. Im not sure of the root cause. I was getting different trouble codes each time checking up to about 20 different codes. Change fluids twice before giving upend found this. Without listing all the symptoms leading to the final nail in its coffin here is the last thing I found. After removing a cover an the back of the transfer case gaining access to the out put speed sensor area I found two and a HALF small roller bearings measuring about 3/16in long by 1/16in diameter. With something that small I would imagine pieces could be every where and I now need a complete rebuild. But I lack transmission knowledge.
Does any have any advise or experience with this, none of the local Detroit Allison shops have any experience with this model or seem interested in helping. Allison does not rebuild this model so if anyone could point me in a direction of a company with experience or knows of a better solution I'm all ears.
I would greatly appreciate any wisdom or advise you would be willing to share!
I ended up purchasing a used one, instead of getting it rebuilt. I haven't installed the new/used one but I'm very nervous about what fluid to use not knowing what caused the problem to begin with.
Thanks
Keith
M1078A1 2003yr
M38 1951yr

 

[Suprman]

Allison lists approved fluids on their website. I go with the stuff right from the Allison dealer Transynd if I am swapping fluid. I have not changed the fluid in any of my lmtv trucks though.
Will

 

[Keith Knight]

Has anyone actually changed out to the Transynd or any other DexIII fluids and have some serious miles logged (over a 1,000) with the new fluids?

 

[Waltjg]

I'm just having a really hard time accepting that switching from motor oil to Dex-III has caused the problem. From what I understand, Dex-III is SAE-10 motor oil with many additives to make it better suited for transmission and other hydraulic applications. I didn't mention it earlier, because it was a fleeting symptom, but I did have an issue one day a few weeks ago (while motor oil was still in the tranny) were I had to shut the truck down and restart to change gears. Before changing the fluids I had only driven the truck maybe 3 miles, because I wasn't driving it until I did all the servicing. Also, I noticed when I dumped the tranny, that it was ~5 gallons low. I actually completely forgot about this because b/w the drain/refill and my "flush-run" I had about two weeks of air-brake troubleshooting before it would roll again...

 

[Waltjg]

...I checked the trouble codes last night, am getting three codes related to faulty temp sensors...

 

[Suprman]

Your best bet is to have the Allison dealer take a look at it. Also the wire harnesses can get some corrosion on contacts over time and that can create all kinds of issues. The allison dealer has plug in diagnostics.

 

[Waltjg]

Yes. I've been talking with my local Allison Service Agent about getting it in for them to look at. So he is prepared for what I am bringing him, I emailed him one of the threads on here where yourself and Tennmogger were discussing connecting the diagnostic equipment to these trucks: http://www.steelsoldiers.com/showthread.php?141873-Diagnostics-port-LMTV

 

[NDT]

5 GALLONS low???? I suspect if the Army was driving it around with that much oil missing, something got burned up.

 

[Waltjg]

That's what I am afraid of. However, there were no metal in the oil at all, was actually very clean...

 

[Overdrive]

I did the transmission fluid swap to ATF but I only have about 40 miles on the truck since. Will be putting many more miles on it once the weather warms up.

I did a complete write up on the change over and was freakishly careful with three flush and fill cycles. There was no metal found during the swap in the fluid, on the drain plugs or in the filters.

I used Mobile ATF D/M (Dex III equivalent conventional oil) which is Allison C4 approved and listed on the Allison recommended fluids page. I will switch over to Transend when its time for a fluid change.

 

[radbad]

Waltjg - I think something is wrong with the manual listing the fluid volume. I ask dumped way low on a change. I need to sort out why I expected around 11 gallons and only got like 3. We refilled all the way assuming the manual volume was correct - checked the dipstick and it was WAY high. Dumped back out until was at the cold fill line. Have taken it around the block a few times and it shifts on our truck.

I think you've overfilled.

Also, not to beat a dead horse - everyone is right when pointing out a fluid mismatch. Allison recommends some super expensive fluid now, but if what I suspect is true, you only need like there gallons of it, not the 11 gallons at $30/gallon I bought:-/. However - I agree that it's unlikely that's causing your shift in issue. The shifting may be an overfill issue.

Lastly - the reason to use the correct. Fluid is that dex3 eats through the seals on the transmission.

Gotta run. Will message you later. Let's swap numbers and chat a bit.

 

[Waltjg]

radbad, Thank you for your post! I have solved this problem, and have been planning a write up to post here, but have not yet been able to make the time to do it yet. some of your finding are indeed correct--and your idea that my problem was due to overfill was exactly correct! My truck shifts awesome now, wayyyyyy better than it did on the motor oil. The Dex-III is ok in these xmsns; Dex III is basically motor oil with some additives--mostly anti-foaming and anti corrosion. I can find the references for this and post them later. I'll have to look this up again too, but I believe it is the synthetics that are not good for the seals on these xmsns...

Regarding your comets about the fluid capacity, I had the exact same trouble, but figured it out... Was befuddled that I was only able to get less than 5 gal out of it, when the manual said I should get ~8 gal at fluid change. Again, I plan to post a write up of my findings, but there are two important things you have do to when you dump the fluid: The xmsn has to be hot--not just the engine hot, you have to drive it a few miles right before you dump. Second--you have to dump, replace the plugs in the xfr-case and the xmsn, let it set a while, open them both again, plug em and let them set, then open them both again.... Each time I let mine set, I went on to other things, and it ended up setting ~48-72 hours. Each time I opened I got about a gallon out of the xmsn, and about a quart out of the xfr-case. I was able to get over 7 gal out this way.