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720 clutch problem...I think?

O

old fashioned farmer

Member
Howdy,

I am having an issue with my 720 diesel clutch. When I go down a hill the clutch seems to let go and the tractor will roll down the hill until it reaches the bottom at that point the clutch will grab again with no interference from me and the tractor will continue on at the same speed as the top of the hill. I have re-worked the crankshaft endplay to it's correct setting, replaced the clutch dogs, t-bolts, and springs, re-adjusted the clutch (which pops in and out and engages great). I am about to pull my hair out on this one. I appreciate any ideas.
 

If the clutch is toggling over-center, it should have no way of slipping..

Are ya sure it is not slipping out-of-gear..?? That 720 D engine is pretty good a holding-back on a down-hill...

Ron.
 
Any chance the over/under drive shifter is kicking out? Just an idea...of course for it to come disengaged and then engaged without any grinding would be near impossible. If your clutch engages fully and stays snapped over center it wouldn't be physically possible for it to be the issue you describe.

Does the issue present in all forward gears?

How about reverse?

Tyler in IL...scratching my chin too...
 
What condition is the clutch adjustment plate? I rebuilt one about 2 years ago that slipped as you describe. Found it to be a dirty aftermarket friction disk on an oily plate. Replaced the wearable parts, springs, disks, ect. Cleaned with acetone and brake cleaner, reassembled with new plates from Deere. Put just a film of graphite on the dogs. Adjusted properly. Problem was solved.
 
Plates all look good. No oil or anything like that. Just the usual dust found in a clutch like that. I get good contact when I snap her in. It's just like when you
are going down hill things get to turning too fast for it to hold the tractor back but when it slows down the friction comes back. I would think that it would slip at
other times if it were a disk issue. I can pull a good load with it and no slippage at all. Just going down hill.
 
I know I've seen you post on your problem before but I can't remember if I'd said anything.

I don't know if you really have a problem. My 70D and 80D both don't have much "hold back" when going down hill. Once at the bottom, travel continues as normal. I know it was discussed way back when on the now defunct Green Magazine board, and others noted the same thing, saying that diesels don't seem to have much hold back. They are easy to over rev and throw governor weights if you don't throttle down soon enough and be ready with the brakes if you are going downhill with a bunch of weight.

Brandon
 
Thanks for the reply. I had not heard that before. Unfortunately, this old bird didn't used to do that. It is better now since I have totally rebuilt the brakes. My wife had a bad run with it last year baling straw when it did its thing going down hill and I hadn't yet rebuilt them. I am wondering if it is in the transmission. I had to do some work on it a couple winters ago and that problem started afterwards. I need to study my shop and parts manual to see what in there could possibly do it. My first thought after it started was the crankshaft endplay was off since I had to remove the flywheel (taper loc) to get in the tranny. I have since found that the collar on that flywheel was bad and replaced it along with fixing the endplay issue. That still did not stop my problem. I moved on to the clutch and found worn parts in there that needed replacing. I just finished that yesterday and the problem is still there. So, I guess now I go back to the transmission and see if I screwed something up in there during re-assembly. Grrr.
 
Don't know anything about a 720 but gear slipping I do. All it takes is matching engine speed to the drivetrain speed and your little finger will pull it in with no resistance at all. That's how we used to drive vehicles in when there was a clutch issue. IF this is your problem it will be the one common drive gear since it's doing it through all of them. Good luck.
 
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