Dead Transmission on M923A1

[rtk]

If anti-freeze mixed with the trans. oil because of a bad cooler , the trans is probably NG . The anti-freeze takes the friction material off the clutches and bands . The shudder maybe a loss of pressure issue . I would do a fluid and filter change and see what you find , it's the easiest and first step . I would also get a pressure gauge and learn how to check the trans. pressures , it will tell you quickly what is going on in the unit . good luck

 

[Ddmk18]

I know your probably looking for a used trans if yours is bad but my dealer cost at napa is $2300 for a rebuilt with warranty unit. I didn't think that was to bad for what it is.

 

[5tonman1971]

I think that's what I suggested in the first post to drain the fluid to check for contamination or a bunch of friction material. If it has 10wt oil in it I would replace with 10wt oil. If you want to have it changed to dexron please take it to an Allison dealer Becuase trying to do it your self WILL cause 100% failure if all the 10wt oil is not removed first.

 

[wreckerman893]

If you want to have it changed to dexron please take it to an Allison dealer Becuase trying to do it your self WILL cause 100% failure if all the 10wt oil is not removed first.

How do you purge all the 10wt out? I replaced my 10wt with Dextron but have not driven the truck much because the transfer case is bad. When I drained the 10wt I let all of it drain out (kept the plug out a long time until nothing was coming out of the drain hole).

Insight please.

 

[162tcat]

Why would having the 10 weight and the dex mixing cause a complete failure?

 

[5tonman1971]

How do you purge all the 10wt out? I replaced my 10wt with Dextron but have not driven the truck much because the transfer case is bad. When I drained the 10wt I let all of it drain out (kept the plug out a long time until nothing was coming out of the drain hole).

Insight please.

How much came out? A dry system takes about 4.75 gallons so anything less then let's say 4.5 gallons you didn't get it all out. If you do not have a pressure filling Machine where it pumps old oil out and replaces it with new at the same time.

but you will have to drain all the lines to the cooler and figure out a way to drain the torque converter and yea so on and so on

 

[5tonman1971]

Why would having the 10 weight and the dex mixing cause a complete failure?

transmission fluid such as the synthetic dexron and 10wt oil do not mix and will cause the friction material be wiped out and will not build correct pressures.

theres many, many posts where people have tried to do it them selves and they get in the truck and boom nothing.

 

[doghead]

A coolant system pressure test may be helpful.

 

[162tcat]

How would Dex and 10W not mix? I've never heard that before. Dex should have a similar viscosity as 10w and both are "oils" so I don't see why this would cause harm.

 

[Coffey1]

OK this is what I read on Allison web and a couple other places .

Dex is find for hi way use
Oil is for off road use (heavy ) due to dex has a lower boil off point.
Allison recommended rotella t 6 for off road use.

 

[162tcat]

I understand that either can be used in the transmission. I'm just trying to understand how they won't mix and how they would cause damage to the clutches.

 

[TXFirefighter]

The fluids do mix! I flush older fire truck transmissions and convert them to the Transyn synthetic fluid all the time. I do this because the synthetic fluid change is worth 10 to 20 degrees of operating temp reduction.
Anyway, for Allison to consider the trans fully converted to synthetic, you have to do an oil and filter change twice. This flushes the torque converter. There will still be some of the old oil in there but not enough to worry about.

Now, back to the NG Transmission. If there was water in the fluid, it would have boiled off during the trip from GA to TX. If the trans cooler was leaking coolant into the trans, it only takes 2 tablespoons of coolant to wipe out ALL of the clutch packs. Straight water will do this too. This is because the glue used in the clutches is a water based glue.
Find a local allison man to come out and do some system pressure checks. With a pressure gauge he can tell you real quick if it is the governor not holding pressure, valving stuck or bad clutch pak.

 

[KaiserM109]

Probably gonna have to wait; we are getting new snow and I have to work outside in a gravel lot. About water boiling off during the drive from GA to TX, I have my doubts that it would because the tranny temp never got that high. I watched all the guages carefully.

Lots of information, thanks everyone. What I have taken from all this is

1. Dextron is10W with additives
2. The Army recommends 10W for off-road use because it has a higher boiling point than synthetics
3. Leaking intercooler could be contaminating the transmission oil (hmmm!)

I have been losing coolant BUT I have a leaky heater core. During my wait for warmer weather, I may pull out the core and see what it is going to take to fix it.

While I have your attention: I also have a short list of missing or damaged parts to replace or fix:

1. Front axle switch: Broken housing
2. Whatever belongs under the 2x3x2 (approximate) box at the bottom of the steering column, something to do with the horn, I believe because my horn doesn’t work)
3. Windshield washer bottle and whatever else goes with it

I’m looking for one person with all the parts so that he/she can stick them in one box and ship it.

PS I also need 1 or 2 of the knobs off of either the blower switch, the battery switch or the starter switch.

 

[wreckerman893]

I’m looking for one person with all the parts so that he/she can stick them in one box and ship it.

PM CSMDavis in Hattisberg, MS. He usually has a lot of parts kicking around.

 

[smittyjr355]

Probably gonna have to wait; we are getting new snow and I have to work outside in a gravel lot. About water boiling off during the drive from GA to TX, I have my doubts that it would because the tranny temp never got that high. I watched all the guages carefully.

Lots of information, thanks everyone. What I have taken from all this is

1. Dextron is10W with additives
2. The Army recommends 10W for off-road use because it has a higher boiling point than synthetics
3. Leaking intercooler could be contaminating the transmission oil (hmmm!)

I have been losing coolant BUT I have a leaky heater core. During my wait for warmer weather, I may pull out the core and see what it is going to take to fix it.

While I have your attention: I also have a short list of missing or damaged parts to replace or fix:

1. Front axle switch: Broken housing
2. Whatever belongs under the 2x3x2 (approximate) box at the bottom of the steering column, something to do with the horn, I believe because my horn doesn’t work)
3. Windshield washer bottle and whatever else goes with it

I’m looking for one person with all the parts so that he/she can stick them in one box and ship it.

PS I also need 1 or 2 of the knobs off of either the blower switch, the battery switch or the starter switch.

I have all these parts pm me if your interested..