I am new to this forum so be patient with me. I have a 1998 750C series ii, with around 8000 hours on it. It starts and runs like a champ. It pushes dirt like it should. BUT somewhere in the electronics there is a demon. YES a demon. When it's traming or pushing dirt it will all of a sudden go into crawl mode and barely move. Shut the key off and restart and it is back to normal. It makes no difference what speed setting it's in. It had developed a track controller problem and I replaced with a reman unit at $3,600.00 USD. It was the only unit that Deere had in the USA. It had this problem before and after replacing the track controller. The pump speed sensor was replaced too along with the FNR switch. All connections have been cleaned along with the fuses. If you turn the key off and back on quickly without stopping the engine it will straighten up. And it doesn't flash any codes either. It does this sporadically, may one in an hour, or once a day. The track controller was replaced because the machine all of a sudden would not move. I despise this electronic bs.
Maybe a moderator will move this to the dozer section for you. You will get better replies if you post up the serial number.
Ok, thank you. Serial number T0750CX940403.
Our resident Deere God can fix this. Do everything he says, and he will have you on your way. When you were checking wiring, did you notice cracks or missing insulation? I also believe when you replace major parts the system needs calibrated which may also be the problem.
I had the TCU calibrated by a tech that worked for Leslie equipment, a Deere dealer. It had this problem BEFORE we changed the TCU. WE ran it today, no problems. Also, we found no loose, broken, or cracked wires. Different techs have worked on it, but no luck. I'm an old school type, I hate electronics on heavy equipment. Big money for the dealers and manufacturers.
Welcome to HEF Old school Jim ! Do you know how to access codes in the monitor? If not, check your messages. Post them if there are any.
There are no stored codes. Very frustrating.
I believe you have an issue with the anti-stall circuitry on the machine. If there are no codes, then the TCU thinks the engine rpm's dropped to a point it needs to dial back the transmissions. When the machine slows down, what is the engine speed in the monitor? When you key on, what numbers appear across the monitor until bulb check is over? I am looking for the software version. When the pump speed sensor was replaced, how did you adjust it? In until it touched, out 1/2 turn? Was the speed ring inside the pump checked to see if it was centered? You said the wiring and connections were checked. Was that visually only, or were voltage measurements made? Wires load tested? Wiggled while testing? Also, is the serial number you provided correct? It is not in the system.
The serial number should have been T0750CX840403. When the tech installed the sensor he did it the way you explained. The speed ring was NOT checked for being centered. As far as the wires go, the plug-ins were cleaned with contact cleaner. I did not get the software version, I'll get that tomorrow.
I have also noticed that when i encountered a problem with pump speed sensor circuit sometimes the speed display on dash would not respond to speed up or down buttons until i key off back on than would start same thing again in a few seconds.