M936 not shifting out of first

[K5Cruz]

Looking to buy a M936a2. Looked at it last week, got approved for a loan saturday. Went to drive it today and it wont shift out of first. Guy says it did this once prior when the CTIS stopped working and shifted normal with CTIS brain unplugged afterward. I looked through the trouleshooting in the OM and didnt see anything that addressed this issue. The fluid level is good. With the CTIS plugged in the lights all flash. Unplugged the cannon plug on the unit and restarted the truck with no change.

I guess my question is this. Does the CTIS have the ability to keep the truck from shifting, or is there a transmission issue here? I havent had much time to do anything other than check the fluid. While driving I let off to try to encourage a shift, ran the rpms up trying to get it to shift, and drove it normally. The trans got up to 190 degrees and remained there. Reverse worked fine.

Any first hand information, tips, or troubleshooting literature would be greatly appreciated. Thanks.

 

[kblazer87]

Did you try shifting through gears manually?

 

[K5Cruz]

Yes sir I did.

 

[98G]

I can't think of a way for CTIS to interfere with the transmission.

Presume you have a transmission problem. I'd have thought maybe the fluid was cold, but you said you got it warm so that rules that out.

The wreckers are heavy, and go through transmissions faster than the cargo variants.

 

[simp5782]

Put transfer case in low range and see if it will shift thru the gears. If it does then you have a pressure problem. So its internal transmission.

Check the modulator cable to ensure it is not broken or the spring came apart.

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[K5Cruz]

I did not think about trying low. Good idea. Where is the spring located?

 

[simp5782]

I did not think about trying low. Good idea. Where is the spring located?

Spring is inside the modulator base on the transmission...you simply replace the whole unit.

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[NDT]

I thought I read this has something to do with converter lockup switch?

Edit: No, that is Stalling in first.

 

[K5Cruz]

He mentioned on the phone that he was able to get it to shift into second on his property, but wasnt able to go much faster. He didnt specify what, if anything, he did. He said low did not make any difference. I'm going to run out there tomorrow and check the modulator and clean the governor filter per the troubleshooting info from allisonparts.net. Hopefully its something simple, but I'm afraid I'll be walking away from this one due to a bad trans.

 

[Trailboss]

Kinda basic, but make sure the PTO is not engaged. When I picked up my wrecker at the base, the PTO was engaged and I couldn't go faster than 15mph. Took a few minutes of checking everything to find it and take it out of PTO, then it would drive normally.

 

[K5Cruz]

He did engage the PTO to run the crane and winches, I did not double check that it was disengaged when I took it for a drive. Would it not shift out of first? Thank you for the suggestion!

 

[Scar59]

He did engage the PTO to run the crane and winches, I did not double check that it was disengaged when I took it for a drive. Would it not shift out of first? Thank you for the suggestion!

Take note, the front winch pto and the crane pto are separate controls. The crane pto lever is on the floor, left side of the drivers seat. Sounds like the crane pto is engaged. Reference the operators hand book (-10).
It is a tricky sequence of control manipulation.

 

[74M35A2]

Tell him to call you when he has it driving correctly.

 

[162tcat]

He mentioned on the phone that he was able to get it to shift into second on his property, but wasnt able to go much faster. He didnt specify what, if anything, he did. He said low did not make any difference. I'm going to run out there tomorrow and check the modulator and clean the governor filter per the troubleshooting info from allisonparts.net. Hopefully its something simple, but I'm afraid I'll be walking away from this one due to a bad trans.

Hopefully the price is good since it seems this guy doesn't know much about it and is trying to make a quick buck. Probably still has the auction stickers on the window.....


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[74M35A2]

Yep, tell him the trans is lunched, and offer him half.

 

[K5Cruz]

He's an acquaintance. He bought the truck from his employer 4 or 5 years ago and it just sits on his property. He doesn't know much about it but I really feel like he isnt out to screw anyone over. He was up front about it having the problem once in the past. The price is great, and honestly would still be a deal with a bad trans.

He worked on it yesterday, said it shifted. I drove it again today, it did shift to 4th. Made an odd downshift to 3rd, and refused to come out of first. The modulator looked fine as far as I could tell. He mentioned bringing a mechanic out to look at it, or just parking it back under the tree and keeping it for use around the house. So nothing useful to add, just a quick update.

 

[Mrsbryner]

Hopefully the price is good since it seems this guy doesn't know much about it and is trying to make a quick buck. Probably still has the auction stickers on the window.....


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I don’t know what gives you the right to say that we are just trying to make a quick buck! For your **** information none of the auction stickers are on it. If you have no helpful information you need to keep your mouth shut!

 

[Mrsbryner]

How do you know the transmission is supposedly lunched? It’s me and my husband selling this. Either have helpful information or stay off the thread.

 

[162tcat]

I don’t know what gives you the right to say that we are just trying to make a quick buck! For your **** information none of the auction stickers are on it. If you have no helpful information you need to keep your mouth shut!

Easy now! I have issue with people buying, driving and selling a huge price of equipment that can kill people when they know very little about it and how to operate it safely. Based on the info so far, you both don't seem to know much about it. Second, this guy is getting a loan to buy this piece of equipment (bad idea in my opinion) so I'd hate to see him buy something that has known issues and get hosed. Best thing you can do is get to know the piece of equipment your selling for your (and the buyers!) Safety.

The military doesn't just throw the soldiers the keys and say good luck.

Commercial drivers don't just jump in a semi without training and hit the road.

All I'm saying is get informed so nobody gets hurt and gives us all bad name!

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[74M35A2]

MrsB, your potential buyer came here and posted asking if we think the truck has transmission issues. Maybe you would be interested in answering the question.