Dead Transmission on M923A1

KaiserM109 · Jan 6, 2014

I just finished (almost) driving the M923A1 823 miles from Dublin, to Denver, CO. For the last two days it showed symptoms of trouble in low gear. It would buck and jump until it got into second. Because of logistic issues, we left it 16 mi. from the storage yard and came back 2 days later, yesterday, to finish the trip.

This time it wouldn’t start moving until the RPMs hit 2200 and it only started forward slowly. I pulled over and checked the transmission fluid again, but, as it was at the start of the trip, it was at the top mark. It started working a little better, so I pulled out onto the street and got into the turn lane. When the light changed, it wouldn’t go forward at all, only reverse. It was like it was in neutral. Just to try anything, I tried shifting the transfer into low range and now I seem to have that in neutral for real; no forward, no reverse. I had it hauled to the storage yard.

The last part of the trip has been cold and the truck spent the last two days before the failure parked at below-zero temperatures. There were no bad noised, no leaks or any other indications of trouble. The transmission temperature has stayed in the nominal range all the way.

Anybody have suggestions? I am going to wait for warmer weather to mess with it. I am hoping against hope that it is temperature related, but even if it starts working, I doubt that I will be willing to trust it off-road.

Questions:

What kind of fluid should I put in it and how much does it take?
What is the civilian equivelent filter for the transmission?
Where do you get a transmission like this rebuilt and what is its civilian model number?

Arlyn

5tonman1971 · Jan 6, 2014

Sounds like you lost first gear or the torque converter went out. The high rpms almost make it sound like it's not building enough pressure to engage the gear. Before ripping the trans out try changing the filter and putting in new fluid. This will A. Verify a blown first gear with all sorts of fun stuff in your pan, or B. You will see a very clogged filter and a simple fix. But I can almost guarantee that you will be looking for a new trans out of a donor truck or forking out the big bucks to have that rebuilt. It might be in your best interest to look for someone parting out a 923 and snag the trans.

5tonman1971 · Jan 6, 2014

Heres a link to a guy in the classifieds parting out a m923a2.

http://www.steelsoldiers.com/showthread.php?117492-Parting-out-another-m923a2

KsM715 · Jan 6, 2014

I would check with BFR Metals (91W350, aka Glen) in Salina KS. They had been scrapping out quite a few of the M939 series of trucks. He may have a trans at a reasonable price. (probably much less than you can get that one rebuilt for)

jasonjc · Jan 6, 2014

Just put a rebilt in a bus last week it was $1350.

DRW1090 · Jan 14, 2014

jasonjc said:
Just put a rebilt in a bus last week it was $1350.

I just bid on one that only drives in reverse. I figured worse case a rebuilt transmission in the future, having an idea of the cost let me decide if worth bidding on. Thanks for the info!

KaiserM109 · Jan 15, 2014

DRW1090 said:
I just bid on one that only drives in reverse. I figured worse case a rebuilt transmission in the future, having an idea of the cost let me decide if worth bidding on. Thanks for the info!

I'm figuring that by the time I get it freighted here and installed it will be around $1000, plus a lot of work. I estimate the transmission is in the 400 lb. weight range and that is a serious piece of equipment to lift. Furthermore it doesn't look like it is possible to go inside the cab with an engine hoist to do the job.

Good luck!!

Does anybody else have comments on swapping transmissions?

Carlo · Jan 15, 2014

KaiserM109 said:
I just finished (almost) driving the M923A1 823 miles from Dublin, to Denver, CO. For the last two days it showed symptoms of trouble in low gear. It would buck and jump until it got into second. Because of logistic issues, we left it 16 mi. from the storage yard and came back 2 days later, yesterday, to finish the trip.

This time it wouldn’t start moving until the RPMs hit 2200 and it only started forward slowly. I pulled over and checked the transmission fluid again, but, as it was at the start of the trip, it was at the top mark. It started working a little better, so I pulled out onto the street and got into the turn lane. When the light changed, it wouldn’t go forward at all, only reverse. It was like it was in neutral. Just to try anything, I tried shifting the transfer into low range and now I seem to have that in neutral for real; no forward, no reverse. I had it hauled to the storage yard.

The last part of the trip has been cold and the truck spent the last two days before the failure parked at below-zero temperatures. There were no bad noised, no leaks or any other indications of trouble. The transmission temperature has stayed in the nominal range all the way.

Anybody have suggestions? I am going to wait for warmer weather to mess with it. I am hoping against hope that it is temperature related, but even if it starts working, I doubt that I will be willing to trust it off-road.

Questions:

What kind of fluid should I put in it and how much does it take?

What is the civilian equivelent filter for the transmission?

Where do you get a transmission like this rebuilt and what is its civilian model number?

Arlyn

i agree with 5tonman and ask did the oil smell burnt? Did you check it at the hot check level? Or cold check level?

Carlo · Jan 15, 2014

KaiserM109 said:
I just finished (almost) driving the M923A1 823 miles from Dublin, to Denver, CO. For the last two days it showed symptoms of trouble in low gear. It would buck and jump until it got into second. Because of logistic issues, we left it 16 mi. from the storage yard and came back 2 days later, yesterday, to finish the trip.

This time it wouldn’t start moving until the RPMs hit 2200 and it only started forward slowly. I pulled over and checked the transmission fluid again, but, as it was at the start of the trip, it was at the top mark. It started working a little better, so I pulled out onto the street and got into the turn lane. When the light changed, it wouldn’t go forward at all, only reverse. It was like it was in neutral. Just to try anything, I tried shifting the transfer into low range and now I seem to have that in neutral for real; no forward, no reverse. I had it hauled to the storage yard.

The last part of the trip has been cold and the truck spent the last two days before the failure parked at below-zero temperatures. There were no bad noised, no leaks or any other indications of trouble. The transmission temperature has stayed in the nominal range all the way.

Anybody have suggestions? I am going to wait for warmer weather to mess with it. I am hoping against hope that it is temperature related, but even if it starts working, I doubt that I will be willing to trust it off-road.

Questions:

What kind of fluid should I put in it and how much does it take?

What is the civilian equivelent filter for the transmission?

Where do you get a transmission like this rebuilt and what is its civilian model number?

Arlyn

i agree with 5tonman and ask did the oil smell burnt? Did you check it at the hot check level? Or cold check level?

BKubu · Jan 15, 2014

jasonjc said:
Just put a rebilt in a bus last week it was $1350.

Where did you find a rebuilt transmission for an M939 series truck for that price? That is a great price. If you can share the source (maybe through a PM), I'd be grateful. Thanks.

tstates · Jan 17, 2014

This may be a long shot, but that cold weather can do strange things to transmissions. I was up In Sparta WI. last week, when it was about -10F Jeff L and I managed to start 5, 900 series Rigs. But one, a M925A2 would not even move for about 2 hrs. It did not like the cold at all. It finally warmed up enough to free up something in the tranny, and it worked fine. Maybe some sticky valves?? Then as we drove it off the lot, the fuel was gelled up and it craped out, and would only run at low RPM. We forgot to treat the fuel. LOL Good luck.

steelandcanvas · Jan 17, 2014

KaiserM109 said:
Questions:

What kind of fluid should I put in it and how much does it take?

What is the civilian equivalent filter for the transmission?

Where do you get a transmission like this rebuilt and what is its civilian model number?

Arlyn

Arlyn, Straight out of the Operator's Manual:

TM9-2320-272-10 July 31 2012 Revised M939 Operator's Manual

Table 9. Automatic Transmission Data.
TRANSMISSION
Oil Type:
OE/HDO 10 -4°F to +55°F (-40°C to +13°C)
OE/HDO 15/40 +10°F to +110°F (-12°C to +43°C)
OEA -65°F to +40°F (-54°C to +4°C)
Oil Capacity--MT654 Transmission:
WO/PTO (drain and refill) 4.25 gal (16.1 l)
W/PTO (drain and refill) 4.25 gal (16.1 l)
WO/PTO (dry) 5.75 gal (21.8 l)
W/PTO (dry) 6.25 gal (23.7 l)
Oil Temperature:
Maximum 300°F (149°C)
Normal Operating Temperature 120°F to 220°F (49°C to 104°C)
Power Takeoff Converter driven

Here's a link to the TM: http://www.steelsoldiers.com/showth...0-July-31-2012-Revised-M939-Operator-s-manual

Gunzy · Jan 17, 2014

I have had a trans guy tell me that he does not recommend a multi-weight oil in the tran(15W40). I am just going to stay with the 10W oil. It has worked fine in service for 30 years and that makes it good enough for me.

KaiserM109 · Jan 18, 2014

tstates said:
This may be a long shot, but that cold weather can do strange things to transmissions. ...

I'm still holding out for long shots. Last Saturday we had to move the truck from its temp spot in the storage yard where the tow truck dropped it to my own little strip. It wasn't warm, but it wasn't so bone chilling cold, either. I was able to get the transfer back into gear and the symptom persisted; reverse worked (which really helped get it into its spot) and forward did not.

I'm still hoping, hoping that it will start working.

KaiserM109 · Jan 26, 2014

Dead Transmission Part II

I am trying one last attempt to fix my failed transmission in my M923A1. In the morning after sitting 36 hr. in relatively cold weather, (~5 degrees f.) the forward gears, possibly only low gear, failed completely, but reverse continued to work. It sounds like my transmission is a goner, but there is still one thing I am hoping for which is contamination, possibly water since the truck was sitting for a year or two in a humid climate, which is to drain and replace the oil and filter. In a search I found this thread:
http://www.steelsoldiers.com/showthread.php?118871-M923a2-oils&highlight=transmission+capacity+m939
There were all kinds of discussions about which is best and it seemed to boil down to this reply near the end:

BKubu said:
I liked your disclosure. I should have used the same thing.

That 10W and Dexron are listed because I was told that the former is basically the latter minus the additives.

All that being said, I am considering draining all the oil and inspecting it for contaminates. I am hoping to find water. If I do, how do I purge it? I will either replace the oil with 10W or put it back. Any suggestions? Either way I will probably replace the filter.

What oil filter should I buy?

doghead · Jan 26, 2014

If you have water in it, you'll also be fighting the cold weather to get it out.

Inside or a week of above freezing would be best.

doghead · Jan 26, 2014

What's the back history on this truck? Did it work beofre the cold weather?

See why continuing one thread is best?

KaiserM109 · Jan 26, 2014

doghead said:
If you have water in it, you'll also be fighting the cold weather to get it out.

Inside or a week of above freezing would be best.

doghead said:
What's the back history on this truck? Did it work beofre the cold weather?

See why continuing one thread is best?

In Nov of 2012 I drove the truck from Ft. Benning, GA to Dublin, TX, 80 mi. south of Ft. Worth. Because of family issues and tire issues with the truck we left it there. Occasionally when starting up from a dead stop it would shudder before engaging.

We left the truck there for 13 months and went back in Dec., 2013 to drive it home to Aurora, CO. On the trip it got real cold and the shudder seemed to increase. A large part of the trip was in temperatures around 10 degrees, f. We left the truck in a Walmart parking lot while we finalized storage arrangements. Thirty six hours after shutting it off, it was about 5 degrees, f and it shuddered bably. In a turn lane right outside the parking lot it failed completely in forward gears.

RE warming it to purge water, I will probably have to wait for good weather. If there is water, where will it accumulate? In the bottom of the transmission? Does it have a pan? Next Saturday I am probably going to drain it and see what I have.

Coffey1 · Jan 26, 2014

I would suspect in oil cooler and trans pan pull oil filter at trans cooler and take inside pour oil out in container and let warm up correct me if wrong if water is in oil would it not seperate.

Ddmk18 · Jan 26, 2014

Yes water is heavier than oil so it will go to the bottom. But if it keeps getting mixed by starting the truck and trying the trans it will take a little while to separate again.

Dead Transmission on M923A1

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