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Discussion Starter #1
Hi guys. I am having a problem with my x748. If I attempt to mow long grass (7 iron deck), the PTO shaft will slow to a stop. Once out of the long grass the PTO will spool up again. Seems to be load related. The greater the load, the quicker the PTO shaft will stop spinning. The PTO light on the dash stays illuminated the entire time. Belt has been replaced on deck, belt tensioner is fine, blades spin freely. Any ideas? PTO clutch?
 

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That would be my guess. Might be Transmission Oil related in that the pressure is not high enough to fully apply the clutch though I think other hydraulic problems would be evident like the steering would be harder to turn.
 

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Discussion Starter #3
Steering can be stiff at idle... I have replaced oil and filter. Could it be the PTO solenoid?

If clutch, would this be a doable DIY fix?
 

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I don't know your skill level though I did a complete disassembly and differential gear replacement on my 445 a few years ago. I would not attempt anything on the tractor without the service manual though. The solenoid would be a simple replacement, though I think JD wants a stiff price for the part. Tough Torque would be a place I would call and get some advice on what is required and for a service manual for the unit. I believe the X7series uses a slightly different TT unit than my 445 though not that much different. Unfortunately, I don't remember the model number of my TT Unit.
 

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I assume you are running full throttle?

Sent from my SM-G900R4 using Tapatalk
 

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I am pretty sure you have the Tufftorq K92 in that. Do you have the John Deere Technical Manual? If not the Tufftorq K92 factory service manual is out on the web if you search for it. This is where I would start.

It could be solenoid but I kind of doubt it. I would think that is going to be a situation where it just won't turn on. Not slipping under load. Fluid level or type could be an issue. You used the correct fluid right? Did this start before or after the fluid change?

Anything can be DIY. It really comes down to your skill level, shop and comfort level.
 

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From the K92 Factory Service Manual. The following are all the troubleshooting items related to Mid PTO. Many don't apply from your description but I am including all of them as maybe you left something out or maybe you didn't think it was related.

Mid PTO Engagement Problems PTO will not engage
  • Check engagement solenoid circuit
  • PTO switch not working
  • PTO lube reduction valve orifice plugged
  • Engagement valve installed incorrectly
  • PTO pressure control valve faulty
  • PTO clutch piston leaking, input shaft seal leaking or clutch disk worn
  • Low charge pump output
  • PTO shaft, gear or bearing failure
Engine stalls when PTO is engaged
  • Excessive load on PTO output. Remove load
  • Use higher engine rpm. Check engine performance
  • Hydraulic circuit in relief. Remove restriction or load
  • PTO brake is not releasing. Check brake piston, Orings
  • PTO shaft, gear or bearing failure
PTO will not stay engaged
  • Check engagement solenoid circuit
  • Engagement valve installed incorrectly
  • PTO clutch piston leaking, input shaft seal leaking or clutch disk worn
  • Low charge pump output
  • PTO pressure control valve faulty
Gear or bearing noise with PTO engaged
  • PTO brake is not releasing. Check brake piston, Orings
  • PTO brake springs faulty
PTO shaft slows down
  • Excessive load on PTO output. Remove load
  • Use higher engine rpm. Check engine performance
  • PTO lube reduction valve orifice plugged
  • Low charge pump output
  • PTO pressure control valve faulty
  • PTO clutch piston leaking, input shaft seal leaking or clutch disk worn
PTO Shaft will not stop, or slow to stop
  • Check engagement solenoid circuit
  • Engagement valve installed incorrectly
  • PTO brake is not releasing. Check brake piston, Orings
  • Excessive load on PTO output. Remove load
  • PTO brake springs faulty
 

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Discussion Starter #8
The problem was there before fluid change. I bought the machine sight-unseen. The machine had done only 100hrs in the last 6 years, but also hadn't had new filters changed in that time also. Machine has 980hrs total. New fluids and filters have been completed and levels are correct. Problem still exists. There is a leak somewhere back there also. Perhaps the machine had sat for a period of time and I'm dealing with a shot seal?
 

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Discussion Starter #9
To back my theory the machine had been sitting for a while, it had recently had a new battery installed, and one of the front tires has that dried out rubber look. The other front tire had been replaced.
 

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You stated that while mowing the PTO shaft / deck slows down and when out of tall grass the PTO will pick up speed. It's rare that any K90 series transmission has a problem, and you're being able service the unit without the service manual is slim to none. So.......

Start by calling the Kanzaki/Tufftorq service group and ask for their suggestions. Then consider that one of the items below will be the problem.

  • PTO lube reduction valve orifice plugged
  • Low charge pump output
  • PTO pressure control valve faulty
  • PTO clutch piston leaking, input shaft seal leaking or clutch disk worn
You also didn't say if you had changed the fluid and filter. I would start there.
 

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Discussion Starter #11
I said in my previous message that I have changed the oil (correct JD oil) and filter, and level is correct.

The transaxle is wet, so perhaps the input shaft seal has deteriorated through lack of use?

Maybe a pressure test through the transaxle test ports may help diagnose?
 

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Discussion Starter #12
Here are some pictures of the transaxle. Appears wet on the bottom half around PTO shaft? Dry up top.
730859
730860
730861
 

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Discussion Starter #15
Not sure whether this has anything to do with my problem, but should that pin on the forward control valve spring back out if pressed in? The reverse control valve does.

730930
 

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Yes they both should. That bar that passes next to them is moved from the side of the frame to push down on those buttons so that you can push the tractor. When you move the bar back out of the way the pins should pop up to allow the tractor to be driven.
 

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I doubt it. It looks like it was up in the earlier photo.

It could be the issues with the leak. As I mentioned earlier the troubleshooting for this is as follows.

PTO shaft slows down
  • Excessive load on PTO output. Remove load
  • Use higher engine rpm. Check engine performance
  • PTO lube reduction valve orifice plugged
  • Low charge pump output
  • PTO pressure control valve faulty
  • PTO clutch piston leaking, input shaft seal leaking or clutch disk worn
Charge pump is on the list so it could be that. Also the last item talks about leaks which you have.

As I mentioned this is from the K92 Tuff Torq Service Manual. You can do a quick search for this on google and will find it. Since it isn't posted by them direct, I don't know what the copy-write status is on it to post a link.

That said I have the TM (John Deere Manual) for the X585 which uses the same transmission and I will say their manual is more detailed on this. Sometimes it is sometimes it isn't. However much of what it talks about and tests are involving test equipment that you might not have.

What is your intent with this machine. Did you buy it to fix and flip? Is it something you plan on using for many years to come. If the latter, I would get the TM.
 

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Discussion Starter #20
I bought it to keep for a long time...

As for the leak. I think it may have been coming from the filler neck. The two bolts were a bit loose...
 
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