850j calibration failure

[Robert Rdz]

Currently have a 850j SN T0850JX143077. At initial start up and after warming up when you place the transmission in forward the will turn a little more than 90 degrees to the left and then start tracking correctly. We tried calibrating it and it failed. Now unless you are in service mode and run the TCU procedures it will not move. Attached at pictures of the codes I have and what it is doing once the TCU procedures. I have 0psi on the left side. Something is wrong on the left side because even during calibrations the pressures mA are less than the right side. If someone can just point me in the right direction to get this thing going. Thank you in advance!

 

[Robert Rdz]

I also have this code stored. TCU 908.7

 

[mg2361]

I believe your issue starts with the right side speed sensor. A typical symptom of a speed sensor failure is a 90* turn before. It then straightens out because the TCU sees an error, sets a DTC, then goes into a default mode to straighten out the travel

I say the right speed sensor (or its wiring) because of the sharp left turn. The TCU is looking for track speeds, sees none on the right side, auto-tracking kicks in stopping the left track (the TCU will always slow the fast track in auto-tracking).

So when calibrating, the TCU is not seeing track speed as it ramps up the mA's during the threshold calibration of the right side, causing the calibration codes.

 

[Robert Rdz]

Thank you. I downloaded the manual and did a lot of reading. I will stop by John Deere today and purchase the sensor. I will let you know what happens afterwards.

 

[Robert Rdz]

Another question we changed out the hydraulic and transmission systems oil and filters. During our last job we noticed that right side hydraulic oil reservoir was close to the top of the sight glass and the left was close to the bottom. We siphon oil out of the right side and filled the left side to the middle and again it did the same thing. Any idea what could be doing that? Thank you in advance

 

[Robert Rdz]

Thank you we replaced the sensor and no more crazy turns. Any idea what would cause the oil on the transmission side to move over to the hydraulic side?

 

[mg2361]

The only place for oil transfer that I can think of is the connection between the hydraulic pump and the hydrostatic pump.

 

[Robert Rdz]

Would that be a seal or something?

 

[mg2361]

Yes. The seal on the hydraulic pump input shaft.

 

[Robert Rdz]

Thank you I will take a look at that. Sucks that I have a busted hand but will figure it out!

 

[Robert Rdz]

So looking at the parts breakdown there is no seal kit for the pump. Do I need to get the entire assembly or do you know if that is a seal kit for that? Thanks in advance

 

[mg2361]

 

[Robert Rdz]

My apologies, what I meant to say once I remove the pump I don’t see a break down of the pump and what parts are needed to fix it.

 

[mg2361]

All that is needed is the shaft seal ("if" in fact that is the issue), but unfortunately, you have to buy the whole kit to get it. It can be replaced without disassembling the whole pump.

Check your messages.

 

[Robert Rdz]

Thank you

 

[Robert Rdz]

So I pulled the pump and sure enough the seal was rolled. Thank you again for all the help. The only thing is that the parts breakdown you sent me that pump looks nothing like my pump

 

[Robert Rdz]

So I pulled the pump and sure enough the seal was rolled. Thank you again for all the help. The only thing is that the parts breakdown you sent me that pump looks nothing like my pump

My bad just noticed it you sent the correct one.