Allison converter locked up

[TTdogs]

I am having an issue with my M923A2. When shifting from Neutral into Drive or Reverse the converter is locked up some of the time. Reverse is worse especially in low range. If it doesn't kill the engine, it will then start working fine until you stop and sit for a bit in Neutral.

This started after we repaired the Hi/Lo lock out switch wire and did some work on the bed. It had not done this prior to that. I changed the fluid to Synthetic Dexron 3 but, I have not changed the internal or external filters since I did not have them.

I use this truck every day and the nearest Allison repair shop is 100mi. away. I am hoping someone has some ideas of some things to look at.

 

[5tonman1971]

Huge mistake on the dexron synthetic without changing the filters.

the military used 10w40 I do believe and if you did not change the filters or get all the old fluid out your gunna have issues, as stated above. Motor oil and transmission fluid don't mix well inside your transmission

 

[TTdogs]

The manual lists Dexron 3 as well as several others all selected by ambient operating temperature range. I will be using this truck in cold months which fits the Dexron 3 temp range. Allison's website recommends TES 295 or TES 389 for the MT series transmission. The fluid I am using is actually Schaeffers 204SAT All-trans supreme which is recommended for use in Allison transmissions specifying TES 295 or TES 389! I pulled the external filter and drained it and blew air thru the cooler to remove additional oil. The oil remaining in the converter is more of an issue than any oil remaining in the filters I would think. I will change the fluid again when I have the filters to further flush the system.
Although this is all separate from my immediate issue. I

 

[bchauvette]

follow

 

[Suprman]

Maybe some gunk in there. I believe the Allison dealer can do a system flush

 

[73m819]

The lock up is electrical controlled, since things worked FINE before you messed with the wiring, I would start there, maybe a loose wire, a shorted wire, WRONG wiring.

 

[DJones]

The lock up is electrical controlled, since things worked FINE before you messed with the wiring, I would start there, maybe a loose wire, a shorted wire, WRONG wiring.