I have a strange problem that has started recently, about every 2-3 hours the right side track all of a sudden starts running at top speed. while the left hand track keeps running at the speed it was set at. The only thing that really stops it is speeding up to max speed, so the way i normally do it is lift the dozer off the ground with blade and ripper and speed up, as speeding away from where i am working over bumpy ground is a waste of time and uncomfortable. Anyone got any idea what causes this?
Had similar problems with 750 and 850s. It was the track speed sensor or something like that. It wasnt reading the track speed right and would speed one side up or down, never knew when it would do it. Just would do it every once in awhile and eventually got a lot worse.
Usually a bad speed sensor causes the opposite side track to lock up or studder. When the TCU loses the signal from a speed sensor it interprets it as 0rpms it will then stop the opposite track to match it causing a quick 90deg turn. I would take the cover off the TCU and leave it off so you have quick access to it, when the machine acts up raise it up like you've been doing. Scroll through the tcu monitor and see what the track speeds are reading. also could note the pcp, steering, and shift solenoid voltages. This will go a long way toward diagnosis.
Sounds reasonable. I recall a paver that would not travel straight. Could find nothing wrong with the slow side but found the fast side signal regularly combined 3 square waves into 1 and as it did the computer interpreted it as a slowing travel and bumped up the speed on fast side. This was caused by a damaged trigger wheel. Look for insignificant damage these sensors are very sensitive and make glitches easily. Later Bob
On the H & J series dozers they always try to slow the faster track down during a mistrack event. The nice thing about the J speed sensor is they are idiot proof for the most part, they only go in one way and there is no adjustment. Plus, they don't fail nearly as often as the H sensors did. The H series you had to adjust the depth and clock them. I don't know how many I worked on that were screwed in too far and damaged the speed ring. Quite a few though. Those were the guys that denied even touching them.
Seconded to check the speed sensor. Try swapping the sensor from left/right motors and see if the problem switches sides. Only other thing may be the motor shift spool sticking, but that doesn't happen as often on the smaller Dozers
this may be beyond my level of technical expertise, i dont know where or what the speed sensor is or how to swap it, and i dont know what the TCU is or what it stands for!
The TCU is the transmission controller. It is under the black cover behind your left elbow when in the seat. If you take the cover off you will see a small display and buttons. You can very easily check the TCU fault codes which might be a good way to start. I'm not sure I'd worry about the speed sensors yet unless you have diagnosed it further. They are easy to change but are not cheap. I'd hate to change one that isn't bad.
Heres where the tcu is and screen for reading codes as long as it is an older j. The new ones can be read on the monitor.
I just replaced a speed sensor on my 700J, it was doing what Deeretracks described. It would lock up one track and do a 90 deg turn, but it only did this with-in the first couple of minutes once you started to work. If you let it go (as long as you had room) it would straighten itself out,it would then show a 372(miss-tracking) code on the TCU. You could still operate the dozer but it steered a little weird. If you shut the dozer off and started it back up it would do the same thing. Yours sounds like something different, then again if you look in your operators manual there are at least six different codes for miss-tracking. If you get a code that would sure help track it down.........Oh by the way those speed sensors are about $250.00 ec for a part you can put in your shirt pocket.
Got it figured, it was showing an error code, F383 which means right side speed sensor. and that there is a circuit problem. i took the chair and floor pan off and cleaned it all up and checked all the wires which seemed to be all good. and made sure all the plugs were nice and tight and correctly connected. put it all back together and ran for a few mins and the error code didn't show and the right track didn't take off, but i really have to go run it for a few hours to see if it works.
started it up this morning and it was displayting the code F382, which is basically the same thing as the f383. and the right hand track was randomly taking off at top speed. the nearest Hitachi technicians are 3 hours away, charge $90 per hour for travel and $120 per hour for work. so it looks like to get a tech to haev a look it will cost nearly double what a new speed sensor will cost
Double check your wiring as that code could be wiring or sensor. I've seen those 3 wire duetsch connectors pull out of the pins a bit and cause intermittent codes. Rather than flipping the seat up depending on your rear attachment I find it easier to squeeze into the rear of it with the cover off. To see if its is the sensor or wiring cut the zipties and you should have enough wire to connect the left wiring to right sensor and right wiring to left sensor. If it still throws the same codes for the right side then you know it is the wiring and if it moves sides then you know it is the sensor.
I've done the wire swap lots of times on H's. Aren't the pigtails a lot shorter on the new style sensors for the J's? Not sure they'll reach. I was capstone certified on the J's when they came out but haven't worked on one in a while. All we have are 750's/850's. The h models had all kinds of issues with the harnesses rubbing thru where they are zip tied to the frame not as much of an issue with j's though.
It has rippers on the back of it, I don't get what you mean by squeezing into the rear, I didn't actually find the sensors when I took the floor pan off. I was just checking through the loom in the middle of the dozer. I'm not sure how to access the sensors, or the wiring near them. I don't actually even know where they are.
The cover Im talking about is on the back bellow the fuel tank depending on whos ripper is on it depends if they cover it or not with the mount. You can also remove the lower panel and still access them. The speed sensor is on the motor at the back and should be pointing to the rear of the machine. Should have a pigtail with three wires and a triangle connector. I'm pretty sure they are the same length as the h series but as you say its more common to work on the 750j/850j series. Ill have a look at my capstone course book sometime. Where are you located thetabop?
If you can't squeeze through the back of the ripper, you can access the drive motors through the plates in the bottom of the machine. There should be 3 under there in the very back. One sensor will be easy to get to the other you may be working blind. They are only held in by 1 allen head bolt each. And from the looks of the pic they do still have the long pigtail on them that will be all bundled up. I would still like to see what the sensors are reading when it happens. I attached a print of the TCU tree hopefully you can read it. You'll want to go into DIAG and scroll thru to Lmtr and Rmtr to see the motor speeds. Also write down and other codes you see in there. View attachment 20140311082409296.pdf Andrew, are you still a dealer tech? Can you do a DTAC search and see if anything pops up? I don't remember coming across this issue before and I've worked on a ton of JD dozers.
I live in Victoria, Australia. We have a large modified ripper on the back that is too heavy to move around on my own, so I got in under the dozer. I found the right side sensor, all the wiring looks good. It however doesn't seem to have the pigtail of wire there, and I don't think there is enough wire to swap sides, I could take the sensor out and swap it with the left one? but i'm a bit worried about damaging them as I haven't handled them before.
You can't really mess them up on a J. Just remove the 1 allen bolt and pull straight out, you may have to twist it a bit to break the oring loose. You will see the flange the bolt goes through is an odd shape so it will only install 1 way. Make sure to relieve the air pressure in the hydrostatic oil tank and be prepared for oil to flow out of the hole when you pull the sensor. I'm pretty sure if you follow the wires you will find an extra 10" or so of wire bundled up with zipties. It's no fun changing them on a dozer with a ripper or winch. But the ripper makes it way easier to recalibrate it later.
I think the wire swap will work. I can't find anything with the same symptoms but I would chase the codes first which according to the book can be a speed sensor. First thing id do though would be the wire swap and go from there.
Just a little bit of LOL... OCR...
Well i got the wiring switched. took me a while the get the damn plugs out, spun off 2 bolts when trying to get he covers off, then spun off 2 more putting it back on lol. Managed to get most of them out and bought a tap and die set and chased the threads, put some new bolts in. Stupidly i decided while i was under the dozer in the much i might as well take out the bolts on the other inspection plates and rethread the holes and put new nuts in. spun one bolt off, another is jammed and looks like it will spin its head off too, looks like ill have to buy a bolt removing tool lol. also found out that it is indeed the sensor and not the wiring that was causing the problem, so looks like ill have to shell out $500 or somthing for a new one :\
Got the new sensor, and got it in, had some difficulty getting the old one out but eventually got it with a small flat head screw driver using it as a wedge tapping it in with a small hammer. went out and used it for around 4 hours and no problems. learned a lot while doing it i must say. thanks to everyone for their help lots of the people on here seem to know more then my local Hitachi service center, as nice as they are.