M916 CAT 7155 Problem

[Coldfoot Stew]

I would appreciate some Tech help in regards to M916. I own and operate a mine out of Coldfoot Alaska. I use several M35A3 with the CAT/ Allison set ups. I am sure the area I operate in would cause love at first sight for most of the owners of this type of equipment but it also brings a lot of challenges. Fortunately for me I have a friend,700 Summit, whose hobby is Deuces and he usually has or gets the answers to any problems that I run into. He has no experience with the 916 so he directed me to this thread.

I recently purchased a M916 and trailer to haul heavy equipment up river to the mine. This truck will never see the highway but It will occasionally see the haul road or Ice road as most in the lower 48 refer to it. When I picked the tractor up in Fairbanks it was below zero and after starting and warming up it went forward but did not have reverse.
We put it in a heated shop on base for 24 hrs and it shifted as it should in both forward and reverse. I moved the rig to our storage yard in Fairbanks where it sat for a few months. When we went to move it the same problem occurred. Forward shifts but no reverse. I don’t want to move the tractor north out of Fairbanks until I can find the solution because the cost of getting a mechanic into the mine would far exceed what I paid for the rig.
I have tried to find a mechanic in the Fairbanks area that actually knows what he is doing with this tranny but have had no luck. The CAT dealership warned me to not open the box as they are a nightmare if you don’t know what you are doing. Yes I could take it to CAT for service but it would end up costing as much as I paid for the tractor. Do to the fact that it had reverse when it was in a heated shop I keep thinking the problem is not a mechanical issue. Perhaps someone on this thread has run into this and would be willing to give me some direction.

 

[wreckerman893]

Contact Rracing here on the forum.....he is the Cat Tranny guru.

That transmission is air actuated and has a lot of solonoid and valves in it. My guess is that moisture is settling in somewhere and freezing up causing lack of air to the reverse......but I could be wrong.

 

[goodguyzy]

If I remember right......there is a heater in the tranny. cant tell you exactly where it is and how it works. I believe its in the tm. If you need a spare tranny let me know, i have 5 take outs for parts.

 

[R Racing]

A couple of things come to mind here. The trans has a heater that is located around the manifold. Make sure its plugged in and working !! anything below freezing and it should be on, There is a temp switch on the manifold.If it doesn't Id be looking at the relays and circuit breakers in the dash. Since these trans run off of compressed air it doesnt take much to turn that moisture into ice. If it were me Id put a water seperator on the output of the outter passanger side air tank.There are many poppet valves in the trans. All it takes is 1 spec of ice or dirt to keep 1 from seating. The problem is in the manifold. Id try that first. If it isn't the next step is to go to that same air line off of the outter passanger tank and pump it with a cup or 2 of air tool oil.this will lube up the poppets and o rings and should push out any moisture . Do a search for 7155 Cat on here. I did a write up on adding a filter and oil mister.If you still have issues your going to have to pull the manifold for servicing. I have walked a few guys thru removing them. I don't recommend doing the rebuild yourself !!

Jim