Caterpillar Still Won't Move!!! 951C

Our 951C won't move. Dad was pushing some brush and went to put it in reverse and it didn't move. Put a new pump on that is by the transmission. Checked all the valves we could find. Replaced some O-rings. We're stuck on what to look at next. Still only getting about 120 psi at an idle and not much more at full throttle. Does anybody know of a forum for talking about Caterpillar stuff like this? I know somebody said something before about checking a priority valve but not exactly sure what they were referring to cause I couldn't find it in the book.

Any help would sure be appreciated! Thanks!

Does the 951 have shifter cables going into the top of the trans.? If it's like a 931 with the cables going into the upper part of the trans.,underneath the top cover there's a valve body. The valve body has an plastic orfice with a screen on it and any small piece of foriegn material will plug the orfice. We had a trans. shop in Winnipeg Man. rebuild one of our's and it cost me 8900.00. When I put the tranny back in the cat we only had about 150psi of pressure. 2000.00 dollars later and 2 diffirent mechanics,we figured out that when the trans was rebuilt they were inspecting the valve body and lost the orfice. The orfice cost 2dollars and 50 cents. If yours does have the valve body on top,once it's out it's a wise idea to put air pressure through the ports underneath the valve body and make sure your clutch's are applying properly. This is probably home school mechanics, but I don't have the luxury of test benches and our local cat dealer won't put a trans on their's unless they rebuild it because of contamination reasons.

Ours has linkage that kind of goes to the side...I am pretty sure that there is a valve body up on top like you said though. I'll check into it.

Word of advice: Always start by checking screen and filter first…if clean THEN and only then should you begin troubleshooting.

If clean start with linkage to make sure you are finding neutral. Most machines have a safety feature that if started in gear the valve dumps all but enough pressure to provide lubrication (approximately 100-150psi….sound familiar?) so that the transmission doesn’t burn up while you are messing with it.

Good advice from Terex, but yours does not have the plastic screen orifice he is describing and the valve group in 951C is very basic…unlikely to be the source of your problem.

We can provide all the support you need but would rather go step by step and not get the cart too far in front of the horse.

Wont move

Clean the top of transmission real well and check the valve body..If all of linkage is OK..I would suspect the valve body is leaking or in the wrong position preventing full pressure to the transmission..I would hope the service is up to date and you don't have a plugged strainer, filter or collapsed hose. Was it overheating before it stopped..A sudden stop could also be caused by broken linkage, oil pump or drive failure, pressure modulation relief valve, stuck open or leaking, load piston or differential spool stuck, transmission failure, torque converter, pinion or bevel gears.. Try to keep it simple as most things are..KISS
Let us know

Thanks for the replys. I know the linkage is all moving but I guess I don't know for a fact that it is in neutral. I mean the shifter is in the neutral position but I'm guessing that doesn't tell me much. And yea that pressure range sounds VERY familiar. Screens and filters are all very clean. As far as we know it wasn't overheating.

Sometimes it’s best to disconnect the linkage at the transmission and shift manually with vise grips. My suspicion is that even though the selector says neutral it may not be all the way in detent and the transmission thinks it is in gear.

Here’s how to adjust your linkage:

If the linkage isn't adjusted correctly would this have anything to do with the pressure only at 120 psi?

Yes, my suspicion is that it might be actually in gear at start up which is triggering the safety feature described earlier.

Yea that would make sense I guess. I appreciate it and I'll let ya know what I find out.

Just wanted to let everyone know we figured it out finally. It ended up being the spline shaft going from the torque converter to the transmission. It was wore off almost smooth. Thanks for the replys everybody!