Ok fellas, my 1996 John Deere 750C SN(TO750CX815491) has another issue. When it’s I pull my park lever down into the release position, the right track will creep forward while the left track sits still. If I’m traveling forward and press the decelerator pedal down the left track will stop and the right track still creeps forward. If I’m traveling in reverse and press the decelerator down the right track creeps in reverse while the left track stops. Moral of the problem, if the park lever is down (released) the right track always creeps. Only way to get it to stop creeping is to put the park lever back up. Any thoughts? Thanks in advance.
I believe there is a pump adjustment for that but its been too long for me to remember for sure. You need to talk to MG. He will show up soon.....I think
I’m searching through my tech manual as we speak. Thanks for your input. I’m hoping it something as simple as an adjustment instead of replacing parts.
Do you have the operation and test manual (TM1588)?
Also, are there any codes?
Yes I do have the TM1588 test manual. It has a lot of info, it’s my first time getting into this manual and it’s taking a little time to navigate. Every now and then I get the code F629. I’m looking into that issue as well. I would like to fix the parking lever issue before I move on to the F629 code. My F629 code doesn’t always show up.
The code is for mistrack, but is not the cause of your creep. Most likely it is contamination or a PCP problem. First thing you need to do since it will creep in forward and reverse is perform the hydrostatic pump flushing procedure found in section 9026-25. Make sure your machine is blocked up off the ground with the tracks completely off the ground before performing any tests or procedures on those machines (the flushing procedure will have you do this).
Ok, thanks a bunch. I will start with the flush procedure first. I will get back with you and let you know the results.
Ok MG, I done the hydrostatic pump flush procedure with no success. While I got the cab tilted, I went ahead and actuated the manual bypass levers on the PCP’s on the front and rear pumps and the tracks worked just fine I’m forward and reverse when I done that. What would be your next check? I would like to fix the issue with the right track turning forward when I release the park brake lever first. Thanks!
Did it still creep after moving the levers on the PCP's? If it still creeps (I bet it did) then the next thing to check is the Pump PCP Internal Adjustment pressure (section 9026-25). Has to be 0 - 5 psi Δ (delta or differential pressure in some circles) maximum. Let me know the results then we'll move to the next step.
Yes, it would still creep with the even after I moved the mechanical bypass levers on the pump pcp’s. I will check the pump pcp internal pressures next and get back with you. Thanks again MG!
Hey MG, got a question. With the park brake lever down in the released position my right track creeps forward. When I actuate the manual overrides on both pump pcp’s both tracks work correctly in forward and reverse. So I went to the motors and activated those manual overrides on the pcp’s and nothing happens and the right track still creeps forward. Is this normal for the manual overrides on the motors to not do anything? I’m thinking it’s normal because the pumps aren’t sending and flow to the motors when doing this test.
Correct. Don't bother with the motor's PCP's. Won't do anything if the pumps aren't sending flow. Perform the PCP internal pressure check and report.
I know I probably sound like a pain in the butt, but I’m having a hard time coming up with the test harness and the differential gauge setup to check the pcp’s. I had no luck with my local John Deere dealer trying to come up with that stuff. It says in the book that I cannot just use 2 different gauges. If I knew how the differential gauge setup was made I would make one myself. And I may be able to look at the schematics and back probe the plugs with a needle to get my electrical readings. It’s a pain in the rear doing these test procedures without the special equipment. Sorry for the inconvenience but do you have any options or information on the differential gauge setup or test harness’s? I’m very mechanicaly inclines as I am a heavy equipment mechanic. Just don’t have the special tools.
To check the PCP internal pressure no wire harness is needed. You are looking at the PCP test. Move down one step to the internal adjustment. Follow that procedure and just check the pressure without making any adjustment. For the pressure, you can use one gauge (0-300 psi). For the cheapest route, just get a Tee fitting with the gauge connected to the center, a ball valve on each side of the tee with hoses from the ball valves to the test ports. With one ball valve open and one closed measure the pressure on one side then close ball valve for that side and open ball valve for the other side and measure that pressure. Subtract the difference and that will be your Delta pressure. Or if you want to spend some money this would work. https://www.amazon.com/OTC-3492-Hea...t=&hvlocphy=9007201&hvtargid=pla-433892704262 At our shop we use a Parker Serviceman setup....$2500+....OUCH! But it is real sweet.
This is one I put together.
Ok, yea I’m totally fine with making up my own. I actually have two 0-15 psi gauges if I just wanted to test each port. I was planning to hook one up to each port until I read where it said not to in the book. Thanks guys. I will probably make one up like parts and service did.
Make sure to use the 300 psi gauge like in p&s's picture. Transmission charge pressure is what feeds that PCP although the actual pressure you read per side in the test should be much lower due to the orifice effect from the internal flapper.
Ok fellas, my front pump pcp tested bad. The pressure delta was 40psi. This is what was causing my right track to creep when I released the parking brake lever. I ordered one today. There not cheap ($1,216 before tax). Once I get the new pcp installed I will re null the pump and then do the calibration procedure and see if all is well. I was getting a F629 code for left track misstracking. Do you think this bad pcp causing the right track to creep is the reason I’m getting the F629 code for the left track? Just curious. If not I will have to move on to that problem next. Thanks for all of your support and help so far!
Get your PCP fixed first (make sure the Delta pressure is good). Make sure the null adjustment is good, then calibrate. Lets worry about the F629 if it returns after that.
Ok, that’s the same thinking I had. I will get back to you with the results as soon as I get the all this done. Thanks again..
Hey MG, while waiting on my 750c parts to come in, I decided to go ahead and service my other dozer (2000 John Deere 650H SN T0650HX888572) while its home from the job. When checking my final drives, my right side had excess oil come out. I just changed the oil 655 hrs ago. So I’m pretty sure the hydro motor is leaking into the final drive gear case. Do I have to replace the hydro motor assembly? Or can I replace seals in it? Machine has 8318 total hrs on it. I don’t have a tech manual for this machine but I’m looking to purchase one. Not sure if I can remove this motor from the rear access cover or possibly have to remove the cab. My luck isn’t all that great lately... haha
Yes the shaft seal can be replaced. The motor comes out the back through the rear access cover. With 8300 hrs I would be concerned that the motor may have excessive leakage causing the seal failure. If you get a manual (I would recommend both the repair manual (TM1744) and the operation and test manual (TM1743). Then the transmission efficiency test can be performed to determine if there is excessive internal leakage in the closed loop. Or if you have a reputable hydraulic shop nearby who can test or inspect the motor I would have that done. By the way your serial number is not in the system, is it correct?
My bad. The serial number is T0650HX888562
T0650HX888562, that's better.
MG, I replaced my pcp on my front pump today. I started the machine and released the park lever and the right track still creeps forward. According to the mistrack flow chart, after I replace the pcp it says to renull pump pcp and calibrate. Is this telling me to renull the new pcp valve? Or renull the pump itself? I assumed that the new pcp valve would come set to neutral.
Hey MG. I think I got it figured out. I checked my new pcp valve and the differential pressure was exact. So I moved on to the pump null adjustment and once I completed that it seems to do what it should. Now when I release the park brake, both tracks don’t move. Only move once I put the FNR lever in forward and reverse. My next step is to calibrate the Transmisson controller tomorrow after I replace a speed sensor on the right rear motor. Will keep you updated!
MG, before I do my calibration procedure I was performing the pcp manual override test on both motors. I released the park brake, put the FNR lever in forward with engine idling, both tracks rotate but when I move the manual override lever on either pump nothing changes. My test manual says that one way should be no change in track speed and moving the lever the opposite direction should increase track speed. Any helpful tips on this?
Did you mean the motor PCP? My suggestion is to ignore that and just perform the calibration. If there are any issues with the transmission circuit it will show up during calibration and also give you a calibration DTC.
Yes, my mistake. I meant the motor. I’m headed home from work this morning and it’s supposed to be get up to 67 degrees here In Sourhern Indiana. I’m going to do the calibration procedure today
Ok, so I attempted the calibration procedure. My machine has the 800 program and shows machine number 03. So according to my manual, the 700 or higher program number has the single lever steer with speed in grip. Mine is single lever steer with speed control lever. I tried to calibrate with the 556 program which matched my serial number but when I got to the step where 45E was supposed to be displayed it only showed 4E. So I went onto the calibration procedure of single lever steer with speed in grip prog. Number 700 or higher. Only issue using this procedure is when I get to step 3 is says to push the buttons up and then down on the FNR handle. I don’t have the speed in grip control on my machine. I’m confused what to do. I was told this machine had series 2 updates when I purchased it. I’m guessing this 800 software is part of the updates. I would like to switch this machine over to FNR with speed in grip but I’m not sure if it’s possible.
Check your email.
Hey mike, I finally had some more time to work on my 750C. I did go ahead and purchase a 2012 750K a few weeks ago because I was in need of a machine and 750C is still not right. So, I ended up replacing both pcp valves on the hydrostatic pumps, and have also replaced both speed sensors on the hydrostatic motors as well as the speed sensor on the hydrostatic pump. I did get my mistrack issue solved. Only issue I’m having now is that once I get through the whole calibration process I get the code “fr” which means that it didn’t calibrate maximum ground speed. And it’s like the machine goes to a default setting because it won’t go any faster than the 1.5 speed setting. My speed setting goes ahead up to 3.0 but the machine doesn’t go any faster after 1.5. Do you think this may be a controller issue? Is there anyway to test these transmission controllers. A new one is $4000 tax included. I hate to spend that much money when I’m not 100 percent sure if that’s the problem.
I do not think your controller is the issue. If it is a single "Fr" and not 2 "Fr's" that indicates one side did not pass the calibration. Check your PM's.