Allison MT654CR problem

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Codyofok

New member
5
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Location
Oklahoma
I think I am having an electrical issue with the Allison MT654CR in my 5 ton. I was working on pulling a semi out of a shallow ditch on a muddy road when the issue arose. The truck was pulling good but had gotten to a point where it was just spinning so I got out to unchain and get in position to try again. When I got back in and shifted into forward there was nothing, like I had not taken it out of neutral. The yoke on the back of the transmission was not spinning no matter which gear it was in and the engine did not lug like when put in gear. We drug it to level ground and checked the transmission fluid but it was in the operating range. I took apart the panels around the gear selector and pressed the ball switch by hand and it went into gear like normal. I made it 2 miles to an intersection and stopped but when I attempted to go it went into a false neutral. From that point it wouldn’t move itself. The transmission would engage and disengage at random, before I could give it any throttle, almost like something electrical was shorting out. I can hear the engine change tone and feel what I assume is the torque converter locking and unlocking but never for more than a second or 2. I cut the wires to the ball switch and spliced them together but it didn’t seem to help like pressing it did. Has anyone else had this happen? Thanks in advance for any advice/help.
 

simp5782

Feo, Fuerte y Formal
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I think I am having an electrical issue with the Allison MT654CR in my 5 ton. I was working on pulling a semi out of a shallow ditch on a muddy road when the issue arose. The truck was pulling good but had gotten to a point where it was just spinning so I got out to unchain and get in position to try again. When I got back in and shifted into forward there was nothing, like I had not taken it out of neutral. The yoke on the back of the transmission was not spinning no matter which gear it was in and the engine did not lug like when put in gear. We drug it to level ground and checked the transmission fluid but it was in the operating range. I took apart the panels around the gear selector and pressed the ball switch by hand and it went into gear like normal. I made it 2 miles to an intersection and stopped but when I attempted to go it went into a false neutral. From that point it wouldn’t move itself. The transmission would engage and disengage at random, before I could give it any throttle, almost like something electrical was shorting out. I can hear the engine change tone and feel what I assume is the torque converter locking and unlocking but never for more than a second or 2. I cut the wires to the ball switch and spliced them together but it didn’t seem to help like pressing it did. Has anyone else had this happen? Thanks in advance for any advice/help.
There are no electrical parts internally.

Did you remove the modulator cable from the injection pump and pull on it to see if it snapped?
 

Codyofok

New member
5
1
1
Location
Oklahoma
Did you use low range transfer? Check the button on the handle of the transfer case lever to make sure that it has returned out.
I was pulling in low but switched to high before I drove those 2 miles. I’ll mess with the button and see if I can detect a short in it though. Thanks!
 

Codyofok

New member
5
1
1
Location
Oklahoma
There are no electrical parts internally.

Did you remove the modulator cable from the injection pump and pull on it to see if it snapped?
No, but the throttle response is fine. I did check the cable that connects to the arm on the side of the transmission to make sure that it is moving the arm with each gear selection and it is fine.
 

simp5782

Feo, Fuerte y Formal
Supporting Vendor
8,808
1,411
113
Location
Memphis, TN
No, but the throttle response is fine. I did check the cable that connects to the arm on the side of the transmission to make sure that it is moving the arm with each gear selection and it is fine.
Nothing to do with throttle response. The modulator cable pulls when throttle increases or you left off and tightens/loosens a spring in its base to increase and decrease fluid pressure to upshift/downshift.
 
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