M920 7155

[dugger82]

Have m920 with cat7155 transmission it's having shifting problems only way to get it go in to gear is put in a grear then push the black button then it goes in to gear then if you want to change gear pull black button out then change gear and push button back in it just started doing this any help would b great

 

[DJGerry]

Have m920 with cat7155 transmission it's having shifting problems only way to get it go in to gear is put in a grear then push the black button then it goes in to gear then if you want to change gear pull black button out then change gear and push button back in it just started doing this any help would b great

problem is in the shift tower block. there is a carbon fiber plate that has steel rings in it. The carbon fiber plate wears out and allows the air to escape. Take the shift tower apart carefully and see if there is play in the steel rings.

 

[DJGerry]

problem is in the shift tower block. there is a carbon fiber plate that has steel rings in it. The carbon fiber plate wears out and allows the air to escape. Take the shift tower apart carefully and see if there is play in the steel rings.

if there is play in the rings, you can epoxy the steel ring into place as long as it is centered and then sand the block smooth.

 

[dugger82]

problem is in the shift tower block. there is a carbon fiber plate that has steel rings in it. The carbon fiber plate wears out and allows the air to escape. Take the shift tower apart carefully and see if there is play in the steel rings.

U are talking about the shifter in the cab if I move the shifter with the black button in it does make any air sounds at all I u put it 2nd gear push in the black button the start move about 45 seconds later sounds like it's starts making noise like it's shifting and keeps moving

 

[DJGerry]

Definitely check the shift tower first

 

[dugger82]

Definitely check the shift tower first

Ok can u buy new ones some where

 

[DJGerry]

Last I knew even the military was having issues in getting the shifter. best to take it apart carefully and inspect the plate.

 

[dugger82]

Last I knew even the military was having issues in getting the shifter. best to take it apart carefully and inspect the plate.

Just so I'm on same page the shifter in the cab is what I need to look at thanks

 

[DJGerry]

yes its the shifter gear selector

 

[simp5782]

The cat manual is available on here. https://www.steelsoldiers.com/threads/m915-series-trucks-cat-7155-service-manual.201375/

There is a trouble shooting guide in the back of it.

Shifters are generally the first culprit with valve bodies being 2nd and the dreaded broken center gear being the 3rd.

Shifter failures are usually a continuous cycle mode where it just keeps shifting repeatedly.


For your case:
You can try to put some air tool oil into your umbilical cord lines to see if that will loosen stuff up that could be stuck.

Also;

Check your vents on the valve body thru the floor access panel. If any of these are clogged up from debris or critters the transmission will not shift properly or choose a gear either

 

[DJGerry]

Cat-7155-Transmission-Shifter-Assembly

Cat-7155-Transmission-Shifter-Assembly

www.easternsurplus.net

I found this one on line