Deere 7600 tractor (1993) I had to replace the park pawl and gear so I had the powershift transmission out. Its all back

Gina,

Yes, I am okay with waiting.

Thank you,

Harvey

Hi Kevin,

I do not have computer access at the shop so I am not there now. I would prefer to do this on Monday am if that will work for you, but if today is better I can made it work.

I did verify the tow release and it is engaged because when I disconnect it the tractor does not move at all.

Harvey

Hi Kevin,

I was able to get a code, thanks to your instructions, and it is 051. I cancelled it and it came up a second time too.

This time the tractor moved ahead about 6" before it cancels, goes into N and rolls back after approx. 5 sec. The same is true for reverse.

Hopefully the code can help.

Harvey

I did have that sensor out to change the park gear. I visually checked it and the wiring a second time but will check it more thoroughly tomorrow. Your answer sounds logical.

Harvey

Actually, the speed sensor is not sensing wheel speed because there is no speed - the tractor is not moving. My question is way is it not moving?

But this morning I did a though check of the speed sensor and wiring. I jacked the wheels off the ground and when I put it in gear the wheels turn a bit and it shows on the dash - up to .17 mph. before it defaults to N. If I phisically turn the wheels in N it also registers mph. Can I assume the controller uses the same sensor as the dash? When I was doing this another code came up -066. Might that tell us something?

Then I went to the trans again. On the bottom of the trans. value housing are 3 test ports. I tested them:

LUB port shows about 25psi in N & 12psi in F and R.

SYSTEM port shows about 248psi in N and 245 in F & R.

CLUTCH port shows 0psi in all positions.

All of the above test were the same whether the clutch pedel was up or down. The only difference the clutch pedel makes is that the trans does not default to N with the pedel down.

I am questioning this 0psi. I think there should be pressure there sometime otherwise the port would not be on there. It makes me wonder if there is anything relating to the clutch linkage or internal valving. I double checked all that and spring. It seems properly connected.

I am lying awake at night wondering what I did wrong. It worked when it came in the shop. Human errors are often the hardest problems to solve. I might have to take it all apart again and retrace each step. I really appreciate your expertise.

Harvey

Thanks Kevin. The tractor came in because the park brake did not hold, so that is what I replaced - the pawl, gear, cam and all related parts. To do this the rear housing, gear box (I forget the actual name),and transmission had to be removed from the tractor as a unit. Then I separated the transmission from the gearbox and set it aside until the repairs were done at which time I reattached it to the gear box, and assembled the tractor.

To do all this I had to disconnect the engine/trans. drive shaft, the clutch linkage, the main wiring harness plug on top of trans. and all related oil lines. The ones I can think of right now were - the two lines to the oil cooler, ps return line, inlet line from rear housing, and several others from the rear housing. All lines and ports were cleaned and capped,idendified and numbered on removal.

My biggest fear of capping the lines (with plastic caps to keep dirt out and from dripping) is forgetting to remove them before installation so I payed extra attention to that.

I also replaced the oil filers, cleaned the inlet screen and bottom of rear housing and put in new JD oil. As I said earlier, the trans filter was only half full when I removed it which I thought strange. I prefilled the new one.

I hope this helps, thanks again,

Harvey

An operators manual did not come with the tractor but I will try and get one and try the "Come Home Mode". It sounds like a good idea.

Harvey

Finally got an operators manual and tried the come home mode. It did not come home. The tractor did not move any more than before. The trans. did not default to N so it obviously did something to the controller.

I was able to do some diagnoistic pressure tests on the trans. that are from the JD service manager. They all seemed to be okay.

I am now wondering if there is some kind of a problem in the drive line between the trans. and gear box, but I know for sure the tow mechanism works, park works, and PTO works, plus it drives a little bit when put in gear. I am wondering this because I hear a faint rattle in the back of the tractor when idling. I didn't think it an issue before but now I am questioning it.

Thanks in advance for your expertise.

Harvey

Thank you, Kevin for your response. I will recheck the harness again. If that doesn't help I will order the manual and learn every intricate detail as to how that trans mission works and take it apart again to retrace each step.

Harvey

I'm back again, Kevin.

I split the tractor again. When I removed the transmission from the gear box the PTO shaft and trans output shaft stuck temporarily in the gear box and came out of the trans. Before I put them back in the trans I looked inside and saw what looked like an O ring inside. We fished it out and it was not an O ring but looks like part of a seal. It fits nicely on the smooth surface of the trans output shaft inner end. Looking inside there is a seal that has rough edges and looks like no lip or garder spring and the same light brown color. It also is located about 10'' from the back of the trans about the length of the output shaft.

Could this be the cause of our problem? What does that it seal? What is involved to change that seal?

I know these are loaded questions but I appreciate your help.

Yes, Kevin that is the shaft. The part of the seal that was loose fits on the left end or inner end of that shaft. It goes in the back of the trans. about 8".

Thanks for your continued help.

I hope you are back well in commission again.

Harvey

Good Morning Kevin,

I did not stand the transmission on end or roll it - kept it the proper way. There was lots of junk and fillings in the rear housing by the inlet screen but none noticeable by the output shaft.

I found the seal on the web parts book and bought it from the dealer. The inside edge looks the same and is the same color. It is #4 on page 307 in the 7600 tractor manual. The picture shows it as a bushing like #3 but the listing call it a seal so we think a print error.

Regardless if this fixes our problem I think the seal should be changed. How much of the transmission needs to be disassembled to change that seal?

Since the trans does not work properly in either forward or reverse which clutch must be engaged in both directions? I am guessing the output planetary so would that be a logical place to look first? Can that be taken apart without disassembling the entire trans?

Thanks,

Harvey

Hi Kevin,

I am so excited! I think I found the problem - a broken spring pin in the clutch linkage in the valve housing! About a 25 cent part causing so much grief!

It has been a long journey to get here. I finally ordered the manuals on CD ( a lot less costly than the parts people told me originally) and I studied them for hours and hours to learn every detail I could.

Since the transmission was already out I decided to replace the seal before assembling the tractor to do detailed testing. And since the seal was near the back I realized I could disassemble that part only to get at the seal. As I did that I found the B4 clutch discs very damaged, one broken in half, two with no teeth and the third with hardly any teeth and damaged splines. I thought maybe that was it until I found out B4 only engages in reverse. Disheartening! I did not want to disassemble the front part but since I was this far and found some damage I had to do the whole thing. I visually checked every disc, piston, oil galley, valve, every part and finally found the broken pin.

So far it makes sense - the clutch linkage triggered the engaged and disengaged switches so it told the controller (and me) that the clutch was working but it did not move the valve to engage the necessary clutches, thus no movement.

I am wondering if the pin broke because the cable was a too tight. I simply reconnected it the way it was since I did not have a manual at that time. I will be studying that part to properly adjust it.

I need to order all the needed parts so the transmission is still all in pieces. I am "cautiously optimistic" and will really celebrate when everything works.

You helped me a lot to bounce ideas off of and gave me good tips. I talked to three other JD mechanics as well and all of them were stumped too.

Harvey

John Deere call it a spring pin. I call it a roll pin. It is R107252, item #20 in the parts book.

I will keep you posted when it is finished.

Meanwhile, since we have "talked" so much I am interested in knowing a bit about you and how you come to do this work - if that is possible.

I am a 59 year old mechanic who has run my own business since 1985. I have a shop in the rural area in central Alberta, Canada. Most of my work is on farm tractors and trucks that are 20 years and older. I try not to get into computer stuff unless I have to - like this job. There are lots of old 4020's and 9N's that still need fixing and I don't plan on doing this too many more years.

Thanks again,

Havey

( I hope Gina-Mod will let me say this to you.)