I’ve been clearing brush on a steep lot for the past week and a half and noticed some weird action while tracking around. I’ve noticed that every once in a while a track will act like it’s jammed. Motor lugs down, motor goes full relief but it barely has any power. If I let off the pedal and then press it down again the motor has power. When both motors are used it has plenty of power but if you let off on one to gradually turn it just become anemic. All 3 track speeds work fine and in a straight line it’s just fine. I recently replaced the seals in the center joint. That’s the related thing I can think of. There are no leaks anywhere.
Have you checked the case drain on the weak motor?
Have you pulled the oil plugs on the final drives? Bob
Pulling the hose to check for excess flow? It's both motors and sporadic to each side.
Yes, oil is right at the proper level and clean.
I haven't had much time to wrench on this thing. I'm building a rock wall and my tracking has been minimal so not a big deal right now. I did notice that the top roller on the side that is typically weaker is quite sloppy. I ordered a new one. Also I ran the tracks and counted 3 revolutions and they were spot on the 12.5 second standard. Here is a video of what's going on. If I press the pedal down slowly it will often slightly load the engine and barely do anything. When I let off I feel some very slight shuddering. Usually only 2-3 distinct vibrations. If I stomp the pedal quickly it more often than not has power and the motor bears down like it should. If I run both tracks at the same time I always have full power. Could it be the flow combiner or a sticky relief? It just feels like it is not loading down like it should. I apologize for the video quality. I realized it was almost black after I took the video and had to push the brightness way up. You'll get the idea.
Here is the order of operation for the flow combiner valve. My hunch is that something is bypassing when only 1 track is used and when both are used there is nowhere for it to bypass so it works as it should.
I took out both relief valves and disassembled them to look for wear. There was a slight marking on the cone shaped plunger but you couldn't feel it with your fingernail so I don't think that could be the issue. I cleaned and put them back and it seems the same. It's hard to diagnose because the issue is not consistent. The machine tracks straight when operating any function while tracking so I think the FCV is operating as it should. I have a pressure test kit coming and I will check the pressures and hopefully that will lead me in the right direction.
I got my pressure test kit and did some diagnosing. I hooked up my gauge to the test port as it states in the manual and was puzzled that boom down, bucket and right track didn't show pressure when operating. The other functions were fine. It doesn't say anything about another port for those functions although I found one easy enough near the other main supply outlet. This might be useful info? I am only getting the pressure that is spec'd for the boom/swing which is 3700ish when running the tracks where it should jump to 4100. Adjusting the Travel relief valve does nothing other than drop the pressure for the functions on that pump (arm, boom up and left track). I assume that the Travel relief is set higher than the overload reliefs for the individual functions and those bleed off the pressure. I don't think the shuttle valve (E) is switching from the low pressure main relief to the high pressure when traveling since the pressure for both tracks no matter what you do with the travel relief stays the same as the relief valve 26 is set to (Other than Travel). What causing the selector to not switch? Broken spring? It's too late to go tear back into it but that will be the next thing I pull out and look at.
I pulled the shuttle valve out and it looked just fine. No marring and the spring was good too. Any ideas?
So I figured out the Main and Travel relief issue. The shuttle valve is working fine. The manual has diagrams that swap the location of the 2 relief valves. I was using one of the diagrams and nothing was working correctly. When I realized the discrepancy I was able to adjust the pressures correctly and everything worked as it should. I still have the travel issue though. I was able to set the travel relief pressure using the left motor to 4150psi but while tracking around I sometimes only see 1500psi with it stalling out. What's weird is I sometimes notice it start at a low pressure and jerkily creep up to 3500ish. It's still not enough to get the motor to move. I usually rock back a few inches and then step on the pedal and it goes just fine. I can't test the right motor with the same test port so I'm usually just testing the left track. The right track seems to be more reliable. Could the relief valve on the travel motor be an issue? I could try swapping these I suppose.
My title must not be that catchy or I have a unicorn of a problem? If anyone has any ideas of what might be going on I'd be glad to hear it.