766 clutch

My 766 was badly in need of a new engine clutch, which I have successfully installed. It also had a growing difficult gear shifting problem. After installing the new clutch I've adjusted the clutch linkage (hydraulic assist), the transmission brake and the dump valve according to the shop manual. Clutch, of course, performs well but the difficult shifting remains. Now, this is a 40-year-old tractor, so could it be possible that adjustments compensating for 40 years of wear need to be made different from the manual specifications? Could the dump valve itself be failing? Or, could the PSI sensing unit be faulty? Thanks in advance for any suggestions!

Linkage wear could be a factor.

When you say it's difficult to shift, do you mean it grinds or hard to move the shift lever out of gear?

If grinding is the problem, you will need to adjust the trans brake to be tighter when clutch is depressed.

If it is hard to move shift levers, first thing to check is dump valve adjustment. When you depress the clutch pedal, the oil light should come on as the dump valve will also release lube pressure on the transmission.

The next thing to check is the trans brake might be too tight. I would say the proper adjustment for the brake is with trans in neutral engage the clutch(engine about 1,000 r.p.m.), depress clutch fully to apply the brake and count 3 seconds and shift it into a gear. The trans should just be stopping(goes over one or two gear teeth).

Drive the tractor and try shifting it out of gear(on fairly level ground), it should shift fairly easy. Once you get the "feel" for it you can do minor adjusting of the brake until you get it where you want it.

If this doesn't help, it might be the rollers in the shifting cams in the top covers of the range and four speed.

Hope this was helpful.

Brian

YEP . Now i will give you the quick start here , As long as you have 5/8ths free travel on the clutch pedal Your good to go there and since it is 12:30 AM and i am setting here enjoying three fingers of C/R Black i am NOT going to type out the WHOLE adjusting set up that i use that works on i don't care how wore out everything is . So you just do a search in the archives on this page on T/A & clutch adjustment by me or it may be under dump valve adjustment as i have covered this sooooooooomany times over the years , i have it all layed out so throw the bood away and do it this way and your tractor will shift like new.

Thanks, Tractor Vet! Actually, I had your adjustment process copied and printed before I started. It seemed to me that your instructions applied only to the mechanical linkage. Do you apply this process to both the mechanical and the hydraulic assist alike? The manual outlines two totally different adjustment processes.

Yep , the only thing the hyd assist clutch does is make it easier to push down and really was made for the heavier pressure plates . On the 66's with the stubby clutch pedal when you got up to the stock plates on the 14's you better have a strong left leg the 10's were bad enough , then along came heavier pressure plates . Now normally on 766's i have not seen any with the hyd assist around here . and of the five that i bought to resell they did not have one . Hard shifting is all in the dump valve setting and that can be a fine line setting if it is set to tight then ya get a double shift was the clutch is let up and the tractor starts to move , if not set tight enough then you have a hard time getting it out of gear. On ce you have your free travel of 5/8ths inch on the clutch pedal and you get the trans brake set then go to the dump valve and back it off six seven turns , make sure the tractor is in neutral and in PARK . Now start the tractor and at and idle deprees the clutch pedal all the way down till the stop lug on the pedal makes contact with the deck plate and hold it there , the tell tale light should be out at this time if not back the bolt off a couple more turns . Then you start turning the dump valve bolt back in slowly until the lite just comes on . NOW stop and let the clutch up shut off tractor and ADD ONE MORE FULL TURN and lock the lock nut down . NOW you should be good to go .