Help - TN75DA PTO Speed Problem

[ranger2166]

Hey everyone, I have a 2006 New Holland TN75DA w/ mechanical shuttle trans. The PTO speed wont get higher than 490rpm @ full throttle. Manual states 540 @ 1957 engine RPM. At 1957 the PTO is running at 360. I've verified the RPM's of the PTO shaft & engine with a handheld tach and they are within 20 rpm's +/- of the tractor display. I've tried adjusting the cable on the PTO lever to engage it more, then less, with no results at all. I don't see any adjustment underneath on the engagement mechanism. Does anyone have any ideas or input? I'm about to go crazy trying to figure this out!

 

[redman135]

It sounds like the power is not getting to the pto in the first place. Does this model have a hydrostatic powered pto or mechanical?

 

[ranger2166]

I thought that also, should have added to first post that I hooked up our 7' bush hog and mowed a few passes of some tall pasture grass with it a 490rpm and it didn't skip a beat - but the argument could still be made that it isn't getting full power... It is a mechanical pto.

 

[George2615]

If it is a mechanical PTO is it hard to believe the max PTO speed at full throttle is 490. If the tach you used is correct the tractor PTO speed has never run at 540. Have you checked the PTO RPM with a second tach. Is it possible the handheld tach you used is out of calibration. We used handheld tach's at work that had to be sent out to be recalibrated / certified once a year.

 

[ranger2166]

I agree, I am thoughtless as to what's going on. Another thing I should have added is that this has just started in the last week. Used the PTO to run sprayer pump last week and everything operated as normal, ran right around 540 on the display. I believe that it is possible that the hand held tach is off, but being within 20 rpm of the display, at any rpm, tells me that it is "close enough" to confirm an issue...somewhere...