Cat 7155 in my M917....

[Abrant23]

Is RRacing still around these forums?!

Got a 7155 transmission that won’t engage. By all my searches he seems like the guru on these units.

I’ve done all the oiling and such that I have read about but I still cannot get it to engage. When I push the air button in on the side of the shifter it continually makes the same noise as it does when it disengages and engages when shifting. I assume something is stuck and I plan on doing some light TM reading this evening, but I figured I’d toss out a feeler here in the forum for some additional assistance

I can try to upload a video once I get out of the woods and have good service.
Thanks!

Alvin.

 

[simp5782]

Shifter is bad and is the first step in the parts replacement. They are cheap. Mine has done this in the past. Replace the shifter. You can try to take it apart and clean it but I have never been successful even swapping the poppets out.

Member Suprman has some shifters for sale. His email is will at pawning. Com. Do not buy the Ebay ones as some of them came from Ft. Polk and were underwater at some point

Nothing internal on the transmission can cause the issue you are having. Worst case part replacement is a valve body. It your umbilical was bad you would hear the air leak

You can take your new shifter apart and do this modification to it that will allow you to jump 2 gears all the way to 16th rather than just to 10th gear.

https://youtu.be/3p2vVF2ybN8

 

[Abrant23]

Thanks for the reply

I’ll give that a shot. I was hoping for a quick fix as the truck is sittin in the middle of the woods at the moment and it’s gonna be a messy walk back and forth to fix it! Murphy’s law always gets ya!

Thanks again.

Alvin.

 

[simp5782]

Thanks for the reply

I’ll give that a shot. I was hoping for a quick fix as the truck is sittin in the middle of the woods at the moment and it’s gonna be a messy walk back and forth to fix it! Murphy’s law always gets ya!

Thanks again.

Alvin.

Buy 2. I keep a spare shifter in my truck. I know member ponway does as well.

You can try getting the truck to full air pressure. Putting the shift lever in like 4th or 6th gear and repeated slap the shifter or pull on it hard do this very hard and repeatedly and see if itll go into a gear eventually. Sometimes the poppet can stick and the little pivot movement just needs a little more force to get it to work right. A shim under the pivot may have broke. Doubtful but maybe you can get it to lock.

 

[Abrant23]

Buy 2. I keep a spare shifter in my truck. I know member ponway does as well.

You can try getting the truck to full air pressure. Putting the shift lever in like 4th or 6th gear and repeated slap the shifter or pull on it hard do this very hard and repeatedly and see if itll go into a gear eventually. Sometimes the poppet can stick and the little pivot movement just needs a little more force to get it to work right. A shim under the pivot may have broke. Doubtful but maybe you can get it to lock.

Ha! Slapped it into 6th and she caught long enough for me to get it back onto high ground!

Ill be buying a new shifter or three here shortly.

This is why I love this forum. Always someone willing to help a fellow enthusiast out.

Thanks again!!!

Alvin

 

[Abrant23]

Shifter is bad and is the first step in the parts replacement. They are cheap. Mine has done this in the past. Replace the shifter.

Replaced the shifter and she’s going through the gears like a champ! Just loaded up the excavator and Fixin to hit the road

thanks again!

 

[37Foxtrot]

Hi,
I am suddenly having a similar problem with mine. If anyone can help, I'd really appreciate it. It is cold and this truck has never liked getting rolling in cold weather, once warmed up, no problems though. I woke her up and swapped trailers, stopped at the fuel barrel, popped the brakes on and heard some air coming from the foremost vent on the transmission. It ran the transmission low on air which disengaged the transmission while I was filling up. I've put air tool oil in the umbilical cord in the cab periodically and I put a lot down the line here but to no avail. It still leaks air at the transmission. The truck barely rocks but won't move in any gear fwd or reverse. I was starting to smell the clutch so I quit. Is this a shifter problem as well? That'd be a real blessing as I am worried it is much worse. Thank you so much for all the posts you all have made with great information in them.

 

[simp5782]

Hi,
I am suddenly having a similar problem with mine. If anyone can help, I'd really appreciate it. It is cold and this truck has never liked getting rolling in cold weather, once warmed up, no problems though. I woke her up and swapped trailers, stopped at the fuel barrel, popped the brakes on and heard some air coming from the foremost vent on the transmission. It ran the transmission low on air which disengaged the transmission while I was filling up. I've put air tool oil in the umbilical cord in the cab periodically and I put a lot down the line here but to no avail. It still leaks air at the transmission. The truck barely rocks but won't move in any gear fwd or reverse. I was starting to smell the clutch so I quit. Is this a shifter problem as well? That'd be a real blessing as I am worried it is much worse. Thank you so much for all the posts you all have made with great information in them.

Does your transmission have a valve body heater on it? It was designed for cold weather use with the 7155.

 

[royalflush55]

I might still have some of these shifters, but I will have to check.

 

[simp5782]

I might still have some of these shifters, but I will have to check.

Worst case Roy he will need a valve body. I don't think he has a shifter problem

 

[royalflush55]

Worst case Roy he will need a valve body. I don't think he has a shifter problem

Yeah I got one of them too!

 

[37Foxtrot]

I'm no expert on mechanics so please bear with me. It has some of the heater parts, but not everything so isn't functional. It has the heating elements mounted on the transmission but not the winterization kit. I did add an a/c heating element in the transmission itself which has helped, however I tested yesterday and the cord has failed. Valve body sound like the culprit?

Thanks again!

 

[37Foxtrot]

What all could it be? If there’s a simple (less expensive) to complex rundown... where should I start? Thank you everyone

 

[Gralmk]

Hi all, recently acquired a M915 with a trans control issue. I've read everything so far on the trans. Working on getting service manual. My question now is whats the bolt torque pattern. Haven't seen anything except the spec, or do you just pick a bolt and work opposites?

 

[simp5782]

Hi all, recently acquired a M915 with a trans control issue. I've read everything so far on the trans. Working on getting service manual. My question now is whats the bolt torque pattern. Haven't seen anything except the spec, or do you just pick a bolt and work opposites?

4 corners first. Then work your way in alternating X pattern

 

[Gralmk]

Thank You!