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'66 Powershift PTO won't stop at 1900 RPM


 
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Dweitzel
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PostPosted: Mon Jan 28, 2013 4:28 pm    Post subject: '66 Powershift PTO won't stop at 1900 RPM Reply to specific post Reply with quote

Just read through 1500+ posts about the PTO and could not find my exact problem.

I have a recently split/repaired 1966 Powershift 4020. After warming up, at any RPM under 1500, the PTO shuts off correctly. At 1500 RPM, it takes 20-30 seconds for the PTO to stop. At 1900 RPM, the PTO will not stop unless I use a 2x4 to put pressure against the PTO and the drawbar and it will chew up the 2x4 a bit so there is pressure on the PTO to make it turn and not just drag.

I tested the "BR" port on the side and I get 150 psi at RPM"s below 1500 and I get between 155-160psi at 1900 RPM. The gauge shows no residual pressure when the PTO lever is pulled toward me.

Almost seems like there is pressure bleeding past something at 1900 RPM, like a check valve is being held open.

The mechanic that split the tractor replaced the front main seal and said when the front clutch assembly was out, he could look back into the case and the PTO brake lining looked "great".

Do you think I could possibly take one of the washer "shims" off the pressure regulator below the PTO valve? I"m assuming I can get to this easily from underneath the right side of the tractor?

The 3-point operates correctly. I only loose about 10-15 psi momentarily from the CL port when the inching pedal is pressed. Steering works fine.

The PTO will not stop at 1900 RPM, takes 20-30 seconds to stop at 1500 RPM, and pretty much works correctly under 1200 RPM.

I also backed the "stop screw" out from the PTO linkage under the dash to make sure it was not being held open by the stop screw. I have not checked the lower portion of the lever.

Any ideas?
 
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WTW
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PostPosted: Mon Jan 28, 2013 6:02 pm    Post subject: Re: '66 Powershift PTO won't stop at 1900 RPM Reply to specific post Reply with quote

Sir,
The pressure on the PTO BR (BRAKE) test port should be more than adequate to stop a normal PTO clutch from coasting. If clutch pressure is zero when the brake pressure is applied you have one of two possibilities causing this condition. First possibility is the PTO clutch is dragging due to too many plates installed or warped plates and disk. This should not be the case if clutch pack/PTO element was serviced when removed. Second cause is that the PTO brake anchor pin has sheared/broke and PTO brake shoe and piston is spinning in bore when applied against turning PTO idler gear. When the mechanic was inspecting the brake shoe lining he should have checked to see if it would turn. If it did the anchor pin holding shoe from rotating has failed. This is not that uncommon on the older PowerShift transmissions. Good Luck, DW
 
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Dweitzel
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PostPosted: Mon Jan 28, 2013 7:06 pm    Post subject: Re: '66 Powershift PTO won't stop at 1900 RPM Reply to specific post Reply with quote

Maybe I did not explain correctly. The test port "BR" is zero psi when the pto lever is off, and 155-160 at 1900 RPM when the pto is on.

The "CL" port is a constant 155-160 psi at 1900 rpm. The "CL" port fluctuates only slightly when I press in the inching pedal.

If the pin is sheared, why does the pto work correctly when the rpm is less than 1200? at 1200 RPM and below, the pto functions normally?
 
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Dweitzel
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PostPosted: Mon Jan 28, 2013 7:08 pm    Post subject: Re: '66 Powershift PTO won't stop at 1900 RPM Reply to specific post Reply with quote

I'm calling the "BR" port the one to the right and the "CL" is to the left or front of the tractor. I do not have my manual in front of me. I hope I'm describing them correctly.
 
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Tx Jim
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PostPosted: Tue Jan 29, 2013 4:41 am    Post subject: Re: '66 Powershift PTO won't stop at 1900 RPM Reply to specific post Reply with quote


I agree with WTW.
 
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Dweitzel
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PostPosted: Tue Jan 29, 2013 2:28 pm    Post subject: Re: '66 Powershift PTO won't stop at 1900 RPM Reply to specific post Reply with quote

Ok, did some more testing today. Decided to pull the oil pressure regulator from the bottom of the transmission, below the PTO valve. Found 8 shims in the assembly. Removed all the shims, tested the PSI at about 120 and PTO would not shut off at any RPM.

Replaced the 8 shims and inserted about 4 more shims (washers) and that brought the PSI to 180-185 and the PTO now works correctly.

Now the question is why do I need the PSI on the clutch port to be 30 PSI above the specs called for? Is this going to hurt anything to leave it this high? I guess I could remove a few washers and maybe set it down to 170-175 and see if that works. I could live with some no load rotation and set the PSI down a bit.

One other question, would setting the PSI up this high cause any leaks from the front of the transmission input shaft? I have drips about every 8 seconds coming out the weep hole in the bottom of the bell housing now? :(

Anyone with a powershift care to chime in. How much spin is normal after turning off the PTO at high RPM"s? At 185 PSI, the pto shaft without anything hooked up stops immediately after shutting off the PTO lever? Am I expecting too much from a 46 year old tractor?

Thanks.
 
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Dweitzel
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PostPosted: Tue Jan 29, 2013 4:57 pm    Post subject: Re: '66 Powershift PTO won't stop at 1900 RPM Reply to specific post Reply with quote

Looked at one more thing this evening. Apparently I've been testing the "clutch" and the "PTO" ports. I did not realize the "BR" port is up higher and below the inching pedal. Guess I need to get the snap ring off the pedal and get a gauge on the BR port to see what the brake is actually doing. Stay tuned.
 
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Dweitzel
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PostPosted: Tue Jan 29, 2013 5:02 pm    Post subject: Re: '66 Powershift PTO won't stop at 1900 RPM Reply to specific post Reply with quote

Guess I missed something. Looked at the manual and it appears I've been testing the "Clutch" port and the "PTO" port. I did not know the "BR" test port is up higher and behind the inching pedal. Guess I need to get that snap ring off and get my gauge on the "BR" port to see what the pressure there is reading. I'll put the correct shims back in the pressure regulator and pull the inching pedal and test the "BR" port. Missed that one. Stay tuned.
 
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