Hello everyone, this will be my first time using this platform or any platform for that matter, I've got a d37ex-21 that is having an issue when shifting into 2nd gear wanting to veer to the left. When you first shift into 2nd it will veer left for about 15ft or so and then track straight as long as you dont touch the joystick, if you apply any amount of pressure to the joystick at all it will automatically start tuning left, not sharp but its enough that you have to apply a good amount of pressure to the right to correct it. I have swapped epc's I have played with swapping the epc plug ins to see if one may be crossed, I have checked the speed sensors while they are in the pump amd the numbers came back good as far as ai goes. I have checked the case drain on the left side track motor in first gear and all I got was barely a drip, but I did not try it in 2nd gear because I didnt think of it at the time. Ive calibrated the joystick 100x I've done a complete pump calibration with the machine off the ground 3x ive also swapped the potentiometers in the joystick thinking the one for the steering may have had a dead spot in it amd re-pinned it in the plug so its exactly like it was and still not difference, I've recalibrated the joystick after I did that amd 25x since then just trying to figure it out. I just got the dozer and knew this was an issue but didnt think it would be that hard to figure out but if anyone has any ideas throw them my way and I'll tell you if I've tried it or not lol it's really kicked my butt so far, thanks for any help!!
Does it do it in reverse too? Do you have the service manual? Pressure checks done? What moves the swash plates on those? Did you check the valving, hoses etc? Looks like all you did was electrical stuff.
It does it in forward and reverse. I have swapped epc's i just got done taking the housing off of the drive motor and checked the spools to make sure they were ok and they seemed fine, just recalibrated the pumps and epc's and the joystick amd it still does the same thing. I honestly do not have the equipment to checl pressure on the hydraulic system at the moment but I've also checked and swapped the speed sensors and it made no difference. If you are running the dozer and apply right track pressure it will track straight shifting from 1st to 2nd but if you just shift into 2nd it will veer to the left everytime for about 15 ft or so and then straighten up but as soon as you put the slightest pressure on the joystick it will start veering left and you have to counter that by right pressure on the stick.
Does the joy stick feel sticky at all? I have worked on other machines where the detent on the joystick was out of phase with where the stick should be for what you want to do.
It doesn't feel sticky at all but looking at the real time monitoring, if i sweep left and return to center and then sweep right amd return to center the numbers never go back to the same value I guess I should say. The numbers are in millivolts and when come back to neutral from left it is at 2575mv resting at neutral and coming back from sweeping right to resting at neutral it is 2458mv. That seems like a big difference to me but im not sure how that registers downstream. I guess there could be some play in the joystick but I dont feel much, if you didnt know any difference gettikg in it and running it you probably would never even notice it. Im wondering if I need to replace the js amd see if that fixes it, id just hate to throw 1500 bucks at it and it doesn't fix it but I have tried a ton of stuff so far and nothing has chamged at all.
Is there a way to watch what happens when you are running the machine. I don't know if your machine is digital or analog but Komatsu generally provides a way to monitor a parameter. If you can watch that when your shift into second gear and it steers off and the millivolts are wandering around then that should indicate a bad component.
I did this in the dual monitoring mode, I watched the left and right track charge pressure and the right track pressure/mpa shoots up way higher than the left track while it veers amd then slowly the numbers start to equalize and the machine will track straight with your hand off of the js. If you touch the joystick with any amount of force at all it will start the left veer immediately, it veers enough that you have to counter steer it to the right to make it stay straight. Im wondering if its in the joystick but im not very confident in that.
I'm fairly mechanically inclined and am pretty decent at troubleshooting, but this thing is kicking my behind. You can run the dozer like it is but its just a pain to run and have that veer in both directions when trying to operate it, I like for my equipment to work like it should in case someone else has to use it and dont have to fight issues and it makes my day a little easier as well. If anyone that has great knowledge of these machines is willing to talk on the phone about the machine I'll gladly pay you for your time, I just need to fix it or atleast try before I jave to get komatsu out to diagnose it and have to sell my liver to pay them
Can you watch the millivolt readings? It sounds like charge pressure is being controlled by the millivolts coming from the joystick.
On my D39px24 and D51px24, I had to replace the universal joint on the blade pilot handle. They had to be calibrated, in the monitor, afterwards. Does your dozer have a joystick for drive? Is it electric? Have you calibrated it?
How about from neutral to 1st? Something is causing a delay, if there is a mechanical link to a solenoid or stepper motor or what ever actuates the swash plate it could be a sticky something that causes the delay. Or electrical an RC time constant deal? Just brain storming here. How old is the machine? Electrical wise, electrolytic capacitors can go bad in controllers and cause issues. And can be as simple as replacing the bad one, easy to spot since the failure mode is usually they leak and make a small mess on the board some times.
From my PX24 manual
Yes sir i have calibrated it 100x probably and tried all sorts of different things to see if I can counter the problem but e everything I have tried still comes back with a veer to the left
Id also like to add that when you shift into 3rd gear it veers right, amd will straighten out in the same distance as 2nd does. But the minute you touch the stick it will continue to veer right. So when I shift to 2nd it veers left and when I shift into 3rd it veers right, I know that sound like im joking but thats what it does.
Yes sir i have calibrated it probably 100x but no difference, i may end up needing a new joystick
The machine is a 2014 model i do believe, 5300hrs on it