3-Point Hitch PTO diagnosis

[bernardcuziillo]

I'm still trying to get my PTO to run. The speed selector lever is stuck in neutral, and the trouble is not the linkage, as I've lubed it and can see it straining as it tries to rotate the shift shaft. Since I thought maybe it's stuck because the PTO clutch is not engaging, I did a little more diagnostics on the PTO valve. I verified that the PTO solenoid is getting +12v properly, and the resistance of the solenoid is 7 ohms which seems right (~25 watts). But I don't hear or feel any click from it when switched on or off. (I do hear the relay clicking on and off properly.) I can see that someone has done this previously judging from the mashed release button on the connector. See the photos below.

Is the PTO solenoid supposed to click when switched on and off?

Thanks as always!

View attachment DSC07834.jpg

 

[Roadworthy]

Most solenoids or relays do click when power is applied then again when power is removed. When power is applied a coil of wire is energized and becomes a magnet. It pulls a metal piece against spring tension making a click when it hits the end of its travel. Turn the power off the magnet turns off and the spring snaps the piece to the other end of its travel. You can have burned contacts or disconnected wires but as long as you can apply and remove power to energize the thing something mechanical will move inside.

 

[ericm979]

The gears may be in a position that keeps them from meshing. Try having someone rotate the PTO stub by hand while you gently try to shift the PTO transmission. With the engine off of course.

On my 3725 when the PTO trans is in a gear (and the engine off), the stub does not rotate readily by hand.

 

[bernardcuziillo]

The gears may be in a position that keeps them from meshing. Try having someone rotate the PTO stub by hand while you gently try to shift the PTO transmission. With the engine off of course.

On my 3725 when the PTO trans is in a gear (and the engine off), the stub does not rotate readily by hand.

The stub rotates freely. Assuming that the gear train is intact, it only means that the output shaft and selector collar are free to rotate. The shifter remains frozen. The splines on the shifting parts are beveled so that they can slip easily into gear, and the stiffness of the shifter implies that the collar is stuck on the output shaft since there is some free play between engagements. See the photo below, taken from the 2014- service manual which is much better than the pre-2014 manual which is a damaged pdf file, and is not very comprehensive. In the photo, input power enters the input shaft at top right, passes through the hydraulically actuated clutch, and drives the pinion gears which are in constant mesh with the speed gears. The collar on the output shaft slides left and right under control of a fork (not shown), and links up power to one of the two speed gears.

The PTO solenoid valve is a whole different problem. Does anyone know what type and size the hydraulic flare fittings are on the PTO valve, in case I wanted to put a gauge on it?

 

[ptsg]

Yes, the splines are beveled but most of the times, it's still somewhat hard to get it into gear. Quite often there is the need to bump the PTO switch, to move things around and it then falls into gear.

Can you see the shaft that enters the transmission from the shift lever to the fork inside, moving?

Usually, if the PTO is ON but in Neutral, you can hear a slight rattle coming from the gears, collars, etc. That should give you an indicator if the PTO clutch is engaging or not.

 

[bernardcuziillo]

ptsg, I get perfect radio silence from the transmission and PTO valve when switching on and off the PTO. (And I know the electrical is switching correctly.)

Yes, I can see the shift shaft, and yes I can see it moving slightly as it strains to try and move the fork.

I'm thinking either punt on the PTO since they're dangerous anyway, use hydraulic instead, or asking Dave's Tractors whether they have pickup and drop-off service at 179 miles (2.75 hrs) one way.

 

[K5lwq]

Do you have a light in the dash that shows the PTO is engaged? Also do you have the switch that says auto and manual?

The PTO is not anymore dangerous than any other moving part on a machine. I certainly would not consider it the most dangerous part of operating a tractor.

 

[bernardcuziillo]

Do you have a light in the dash that shows the PTO is engaged? Also do you have the switch that says auto and manual?

K5lwq,
Thanks for the questions. The light does light up when the PTO is switched on. The positions are LINK, OFF, and IND. LINK turns off the PTO with the lift raised or the clutch depressed. IND turns on the PTO whenever the key switch is on. And I've verified that +12v is going to the solenoid valve when switched to LINK, and not when it's off. Also, I can hear the PTO relay clicking on and off correctly. (Also, the starter is disabled by another relay when the PTO is energized.) The solenoid shows 7 ohms resistance.

My PTO auger has no guard on the PTO shaft and nothing that prevents it from telescoping apart. I imagine a flailing PTO half-shaft must be a frightful sight. That's why I'm thinking just get a skid steer auger on the loader, or even better an auger for the backhoe using the bucket circuit for the auger. No craning around to see it, and the rotation is reversible for when it stalls downhole. Plus both the loader and backhoe can apply down force which the PTO has much less of, and I'm drilling in shale and sandstone. All the same, I'd like a functioning PTO.

Thanks again,
Bernard

 

[K5lwq]

They have not changed much then over the years. My lever sometimes will not engage no matter how hard you push on it. So I do as PTSG suggested and activate the PTO switch and then turn it off while holding pressure on the lever. It usually will fall in gear then.

Definitely one of the more Finicky designs I have ever had.

As long as the PTO shaft on your implements is not bent and slides in and out freely, there is very little to go wrong. Just do not get around one that is spinning, especially with loose clothing.

I do agree with down pressure being helpful but, a good bit and taking your time, a PTO PHD will surprise you what it will cut through.

Good luck and I hope you get it going without having to send it to a dealer.

 

[bernardcuziillo]

Problem solved. The fork shaft was seized due to disuse and too-tight clearance. The linkage was not strong enough to break it loose. But luckily, there's a back door to the fork shaft that is accessible at the rear of the tractor under a little plastic cup seal. Just take a long brass punch and 5-10 lb sledge and you can start to move it. You'll feel it bottom out, and the lever will be in the low position. Then go the lower bell crank on the linkage, remove (or break off) the zerk fitting to make room for a huge pry bar. Move the lever up with a big effing pry bar. The roll pin is pretty strong, and I was surprised that I didn't shear it, although I think it would have broken if I had not broken loose the shaft first. Run it back and forth while spraying Tri-Flow lubricant, and it should free right up for you. I'd recommend exercising the lever monthly when not using the PTO to keep your options open. Hats off to Jared of Dave's Tractors for this fix.