problems with pto my jd 790, 5' rotary cutter mower
- Thread starter ram78380
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Welcome to the forum! I assume this is a tractor you have had and the pto has worked ok, or is this tractor new to you and pto has not worked properly? I am assuming the pto clutch is not disengaging when you push the clutch all the way down. WHen nothing is connected to pto, the lever can slip in easily because the shaft can jump in with no load. When mower is connected, the pto shaft has to get a lot of weight spinning so the splines can't engage with clutch not disengaging properly. On the two stage clutch like the 790 uses, most people use the transmission clutch a lot more than the pto and they have to adjust free travel to compensate for wear. The problem is that this gradually reduces the ability to disengage the pto clutch. The adjustment to regain pto operation is inside the clutch housing on the pressure plate. Clutch replacement may be required to fix, but adjustment is possible through a hole on right side of clutch housing... at least it was possible on 70 series tractor. I believe the 790 is the same way.
I've had my jd 790 for 20 years and the pto has never engaged smoothly. Recently I had to adjust the clutch to keep the tractor moving. After adjusting it per the service manual it is harder to engage the pto. Also the pto will not stop no matter how long I hold the clutch all the way down. So far I have not been able to find anything in the service manual on adjusting the pto clutch. Yes it is a 2 stage clutch. Any suggestions would be greatly appreciated.
I've done a lot of mechanical work over the years but have never worked on a clutch. Also this being the first time I've needed to adjust the clutch should I expect a lot of life left or will I be looking to replace it in the near future.
I've done a lot of mechanical work over the years but have never worked on a clutch. Also this being the first time I've needed to adjust the clutch should I expect a lot of life left or will I be looking to replace it in the near future.
beenthere
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Sounds like adjusting the 2 stage clutch is needed to fix the problem. Will need to sort out if it is a linkage adjustment or if some parts of the clutch need replacement. Expect someone will come with more knowledge to fix you up with an answer.
Can you engage the PTO before starting the tractor? And if so, after starting the tractor, does the PTO stage of the clutch stop it from moving?
Sounds like adjusting the 2 stage clutch is needed to fix the problem. Will need to sort out if it is a linkage adjustment or if some parts of the clutch need replacement. Expect someone will come with more knowledge to fix you up with an answer.
Can you engage the PTO before starting the tractor? And if so, after starting the tractor, does the PTO stage of the clutch stop it from moving?
Last edited:
Zebrafive
Super Member
Maybe rust sticking the PTO clutch.
Yes I can engage the PTO before starting. No the PTO will not stop moving when engaging the clutch .
I've had the tractor since it was new 20 years ago and the PTO has never engaged smoothly but since adjusting the linkage which I had to do it is worse.
Is it possible to adjust to adjust the 2nd stage (PTO) of the clutch without splitting the tractor apart?
I've had the tractor since it was new 20 years ago and the PTO has never engaged smoothly but since adjusting the linkage which I had to do it is worse.
Is it possible to adjust to adjust the 2nd stage (PTO) of the clutch without splitting the tractor apart?
Someone on another post said the PTO clutch could be adjusted by removing the screen on the right side of the housing. Not easy and I'm sure it's not exactly to specs but it is much closer now. The PTO still does not stop with the clutch all the way down but it is better. Something I did discover was that when I start the PTO with no attachments it works very smooth with no grinding whatsoever. Love to hear any input as to why attaching a load on the PTO causes the gears to grind.
I would still love it if the clutch stopped the PTO completely but honestly I can't say for sure if it ever did.
Also does any one have any idea how much life is left on the clutch after you have to start adjusting it? This was my first time in 20 years I found it necessary. Hoping to purchase a bigger tractor in the near future but would really like to keep this one for those days when 2 are handy. With the cost of parts I will probably not get another Deere even thought it is a very nice unit and has served me well.
I would still love it if the clutch stopped the PTO completely but honestly I can't say for sure if it ever did.
Also does any one have any idea how much life is left on the clutch after you have to start adjusting it? This was my first time in 20 years I found it necessary. Hoping to purchase a bigger tractor in the near future but would really like to keep this one for those days when 2 are handy. With the cost of parts I will probably not get another Deere even thought it is a very nice unit and has served me well.
The pto grinds when engaging with a load because the clutch is not stopping the pto shafts entirely. Without a load, the shaft jumps right in without grinding due to no weight to spin. If you adjust the three pto bolts to spec through the screen hole, it should work properly. You need to shorten the bolts until the gap between bolt head and clutch plate is .060" which is spec. I like to adjust to about .055" to give a little more wear before it needs adjusting again. Check the gap with a feeler gauge.
It is impossible to say how much longer the clutch will last. SInce you waited until tractor wasn't driving well to adjust, it has substantial wear on it. Clutch probably should have been adjusted 2 or 3 times before to keep free travel in pedal at all times. My guess would be you have less than 1/2 of the life left, but if you keep it adjusted before it starts slipping, you will get the best service from it.
thanks for the advice. I had a difficult time adjusting the pto bolts through the screen opening. I know I am close if not right at .060" but will give it another shot and get it down to .055". There has been some grinding when engaging the pto since the tractor was new so I wasn't sure if it could be eliminated. I didn't know if I could do any harm by adjusting them tighter then the .060 so thought it best to wait for some advice. thanks again