LMTV Transmission Issues

[radbad]

Walt,

Thanks for the reply! I wish there was as much info on this forum about trans fluid changes when we changed ours as there is now!

We did an initial warm drain, got out about 4 gallons, then filled up to what we thought capacity should be (so we overfilled). Took it for a spin - much better shifting. Got back, checked transmission fluid level and found it was very high. We drained a bunch out to get back to the right level, and now we have some sort of mix between the original motor oil and the Transynd.

Our plan now is to drive it for a while at the correct level and see how it drives. Any indication of unfavorable performance, and we'l re-visit another drain/replace cycle.

Cheers,
Brian

 

[Overdrive]

I did a whole write up on this and precise measurements on what fluid came out during each drain & fill. Really have to be careful about overfilling a transmission...

http://www.steelsoldiers.com/showth...ssion-Fluid-Change-To-ATF-Write-Up&highlight=

 

[radbad]

Overdrive - just saw that i never got back to you on my earlier thread. Thanks for bringing the various threads together here. Seems like the next person to do a transmission fluid change will have a much easier time with the background here!

 

[Waltjg]

Overdrive,

Thanks. Nice write up. Now I don't have to do one. I did basically the same process; except I removed the drive shaft. One thing you did that I did not, was put the xmsn in learn mode when I was done. Where did you find the procedure for this?

Thanks again,
Walt

 

[Overdrive]

Overdrive,

Thanks. Nice write up. Now I don't have to do one. I did basically the same process; except I removed the drive shaft. One thing you did that I did not, was put the xmsn in learn mode when I was done. Where did you find the procedure for this?

Thanks again,
Walt

it was in the same TM TM 9-2320-365-20-3 as the trans filter change. Learn mode is talked about when changing the trans shifter dash thingy. It is mentioned several times after procedures in that -20.

 

[MaiNiaK]

The other day I put my M1078 in a ditch trying to back up around some other vehicles on my property. The ditch was about 4 feet deep and I left my truck there overnight, till I could get my other truck with ice chains there to help pull it out.
The truck started a little hard because it was cold out and I wasn't near a plug to plug it in. I let the truck run 20 minutes before we even tried to pull it out. It shifted into gear and drove right out with my other truck helping (no yanking or hard shifting just a nice easy drive out).
I then drove my M1078 back to its normal parking spot and let it run a little while longer, to make sure the battery's were topped off. I then shut the truck off, walked around the other side and saw I was parked on my extension cord. So I got back in the truck fired it up and put it in drive. It went right to 7th gear but was still in nutral and the buzzer was buzzing quietly. So I tried revers, still nothing, it was still in nutral. The only thing I touched before parking the truck was I put the CTIS back in highway and deployed the parking break.
I know I didn't beat on the transmission at all, so I checked my fluid. The fluid was at the right level.
I didn't have my iPad with me, so I was unsure how to check the trouble codes. I will be checking my codes tomorrow first thing.
There has to be some sort of safety features that shut these transmissions down.

 

[Suprman]

Sounds like an electrical gremlin if the low air buzzer was buzzing quietly. Bad grounds bad connections. The trans ecu does not do well without proper voltage.

 

[Overdrive]

Overdrive,

Thanks. Nice write up. Now I don't have to do one. I did basically the same process; except I removed the drive shaft. One thing you did that I did not, was put the xmsn in learn mode when I was done. Where did you find the procedure for this?

Thanks again,
Walt

Waltjg, thanks! Do you have any advise, info on your front driveshaft removal? I would like to have any tips you may have for when I replace the u-joints.

 

[Suprman]

Get the tool. OTC 5190A. Army mechs keep the same style in their tool kit thats what they use to pull the driveshafts. Its too easy to cause damage hammering the ujoints out.
Will

 

[Overdrive]

Suprman that's CRAZY!!! I have that tool in my wishlist on Amazon. I took a guess a while ago before I tried the trans filter change without removing the driveshaft. Weird coincidence. Plan is to get that tool at some point...

When I took my LMTV in for the state safety inspection I was talking to the heavy equipment mechanic doing the inspection and brought up the difficulty removing the u-joints and he also suggested getting a bottle jack under the joint with the caps off and a few pumps would loosen the joint without any damage. Of course you would need a platform to get a jack that high but I thought it was interesting. If anyone has that OTC tool it would be nice to see a write-up with pics.

Thanks!
OD

 

[Suprman]

I have the tool I am working on pulling a trans from one of my parts trucks. Its been snowy the last week or so and its really cold so maybe late next week if it warms up. Its shown in operation online.

 

[MaiNiaK]

Sounds like an electrical gremlin if the low air buzzer was buzzing quietly. Bad grounds bad connections. The trans ecu does not do well without proper voltage.

I had the hand throttle on a little bit, so the tires would air up faster. Transmission works fine with the hand throttle off.

 

[Waltjg]

The other day I put my M1078 in a ditch trying to back up around some other vehicles on my property. The ditch was about 4 feet deep and I left my truck there overnight, till I could get my other truck with ice chains there to help pull it out.
The truck started a little hard because it was cold out and I wasn't near a plug to plug it in. I let the truck run 20 minutes before we even tried to pull it out. It shifted into gear and drove right out with my other truck helping (no yanking or hard shifting just a nice easy drive out).
I then drove my M1078 back to its normal parking spot and let it run a little while longer, to make sure the battery's were topped off. I then shut the truck off, walked around the other side and saw I was parked on my extension cord. So I got back in the truck fired it up and put it in drive. It went right to 7th gear but was still in nutral and the buzzer was buzzing quietly. So I tried revers, still nothing, it was still in nutral. The only thing I touched before parking the truck was I put the CTIS back in highway and deployed the parking break.
I know I didn't beat on the transmission at all, so I checked my fluid. The fluid was at the right level.
I didn't have my iPad with me, so I was unsure how to check the trouble codes. I will be checking my codes tomorrow first thing.
There has to be some sort of safety features that shut these transmissions down.

I know this is obvious, but it got me one day moving one of my trucks around the yard--if the transmission fill cap is not tightly installed, the truck will drive like it is stuck in high gear. It will shift, but the tranny can't build pressure, and all of your power will literally go right out the fill tube. Worth a check...

-Walt

 

[Waltjg]

Waltjg, thanks! Do you have any advise, info on your front driveshaft removal? I would like to have any tips you may have for when I replace the u-joints.

Drive shaft removal/reinstall and/or U-joint replacement is actually pretty easy on these trucks. Only one that I have done was stuck good, and it didn't take too much persuasion. Most tap right out. I always clean off EVERY SPEC of old grease everywhere, and repack full of new.

Advise:
- Most LMTVs have had the drive line upgrade--new style drive shafts and u-joints--but if you happen to have one that has not had the upgrade, make sure you match-mark on each side of the slip joint (the upgraded trucks have a master spline, so marking is not necessary). Check your data plate for a D stamped after the SN; this indicates the upgrade has been done. Even if you have the D, its best to make sure you have a master spline before completely separating the slip joint.
- Remove the dust seal and slide it up beyond the splines BEFORE attempting to disassemble the joint. Inspect your dust seal, if any dry-rot, cracks, or other defects--replace. If it appears to be in good shape, clean it thoroughly; then give it a good going over with pure silicone gel. Make sure to then wipe off all the silicone. This will extend its life. But again, don't leave any excess to get mixed up in the grease. Don't forget to install it before reassembling the shaft. Slide it up beyond the splines, and install it place after the joint is together.

When replacing U-joints, I have been really happy with Newstar S-7434. They are engineered in the US, but manufactured in China (I know, I know...). I've found them to be good so far. Attached is the spec sheet.

I've also uploaded the IPB and instructions. I know everyone has these, but just for ease of reference...

Hope this helps.

-Walt

View attachment S-7434,_UniversalJoint.pdfView attachment TM 9-2320-365-20-3, 9-2.pdfView attachment TM 9-2320-365-24P, Fig. 131.pdf

 

[Overdrive]

I recall reading a few posts about having the RPMs too high (hand throttle on) and the trans not shifting into gear as a safety feature... MaiNiak are you saying that with the hand throttle off, all the way down, your truck shifts just fine?

That being said, when my LMTV was driven off the flatbed on delivery the hand throttle was in the first throttle up position (higher RPMs) and still shifted into gear so who knows.

 

[Waltjg]

Drive shaft removal/reinstall and/or U-joint replacement is actually pretty easy on these trucks. Only one that I have done was stuck good, and it didn't take too much persuasion. Most tap right out. I always clean off EVERY SPEC of old grease everywhere, and repack full of new.

Advise:
- Most LMTVs have had the drive line upgrade--new style drive shafts and u-joints--but if you happen to have one that has not had the upgrade, make sure you match-mark on each side of the slip joint (the upgraded trucks have a master spline, so marking is not necessary). Check your data plate for a D stamped after the SN; this indicates the upgrade has been done. Even if you have the D, its best to make sure you have a master spline before completely separating the slip joint.
- Remove the dust seal and slide it up beyond the splines BEFORE attempting to disassemble the joint. Inspect your dust seal, if any dry-rot, cracks, or other defects--replace. If it appears to be in good shape, clean it thoroughly; then give it a good going over with pure silicone gel. Make sure to then wipe off all the silicone. This will extend its life. But again, don't leave any excess to get mixed up in the grease. Don't forget to install it before reassembling the shaft. Slide it up beyond the splines, and install it place after the joint is together.

When replacing U-joints, I have been really happy with Newstar S-7434. They are engineered in the US, but manufactured in China (I know, I know...). I've found them to be good so far. Attached is the spec sheet.

I've also uploaded the IPB and instructions. I know everyone has these, but just for ease of reference...

Hope this helps.

-Walt

View attachment 607914View attachment 607915View attachment 607916

...Oh, one other thing: These shafts are heavy, it is very helpful--almost essential--to have a second person to help when separating and assembling the slip-joint.

 

[MaiNiaK]

I recall reading a few posts about having the RPMs too high (hand throttle on) and the trans not shifting into gear as a safety feature... MaiNiak are you saying that with the hand throttle off, all the way down, your truck shifts just fine?

That being said, when my LMTV was driven off the flatbed on delivery the hand throttle was in the first throttle up position (higher RPMs) and still shifted into gear so who knows.

Yes. My truck is fine now. The rpm's must have been to high for it to shift into gear. The truck is fine now that my hand throttle is all the way down and not up at the low throttle level.

 

[5tonmog]

98 % of shifting problems are from improper fluid levels. Trust me I am 74 years old and know my stuff!

 

[FSRD]

To remove the caps on my U-joint I popped the top caps off breaking the weld and use a steering wheel puller to press out the U joint. The bolts that come with a steering wheel puller thread perfectly into the holes on the shaft. Make sure you thread them in all the way cuz you don't want to risk stripping them out. This is definitely one of the cheapest ways to go that is an effective and gets the job done easily. I'd much rather play 20 bucks for a steering wheel puller to take care of the issue then to pay $300 for the proper cap puller tool.

 

[samsneed]

I'm at the end of my rope on my transmission also, thinking about either taking it in for service at the Allison dealer or swapping the transmission with a good one I have in another truck. Can the transmission be pulled without jacking up the truck? I'd be doing this in my driveways....

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