656 weak pto pressure

Yellott Canby · Oct 7, 2011

Hello,
Was wondering if anyone had any experience with the pto clutch unit on a 656. I had mine rebuilt and got it back on but when I checked it with the pressure gauge it read only 170 psi or so. If I pry up the actuator all the way up I can reach the desired 210 psi. However when the pto linkage comes over center to lock in the "on" position the pressure falls back to the 170 range again. That 1/8" inch fall reduces the pressure that much. The thing is designed to drop slightly when it comes over center. I just was thinking that perhaps the pto pump gears are worn to the point that in order to reach the needed pressure the linkage must be fully extended. Hate to burn up the new pto clutches for lack of pressure.
I appreciate any thoughts on this.
Thanks,
YC

Janicholson · Oct 7, 2011

Use a shim on the stop on the over center control. Make sure it goes over center and is not in danger of "falling" out of engagement. A flipper and notch could be installed with a rod to lift it when disengaging the PTO. See the lever on a 400 Farmall. I think it will work. The Vet said bend the rod some, maybe this allows it to pull after over center (just thinking out loud) Jim

LarryT · Oct 7, 2011

That is adjustable. If you will look at the parts breakdown on that unit (I am attaching the url to the web page below) you will get an idea of how it goes together and where you can make the adjustments. The spring tension may be off a little but that's easily adjusted. Hope that this will help. LarryT
Case international 656 drivetrain

Yellott Canby · Oct 8, 2011

Thanks for the help.
I believe that all the adjustment is out of the factor actuator rod. When we put it together we tightened the the square head piece all the way down on the rod. I think the only thing left to alter is the piece from the square head up to the pivot piece. It is the slightly curved piece that has a welded pin on the lower end and a hole at the upper. I drilled a hole right under the factory hole and tried it, but it was too low and could no loger get it to come over center.
Then I filled the holes in with weld and drilled one mid ways between them and it was close to being right. Very stiff to engage and disengage, but nearly right on the pressure. Perhaps a strong spring needed pivot piece and the square head.

the tractor vet · Oct 8, 2011

IF ya got the valve stem SCREWED INTO THEW NUT AS FAR AS IT WILL GO THEN YA NEED TO RAISE THE LINKAGE UP ON THE MOUNTING BOLT HOLES .

pete 23 · Oct 8, 2011

Original 806 was set to 185 psi with little problem. Most 656's were hard to get to that point due to the type of linkage they used but I never saw one slip or cause problems at 165 psi. You could go to a heavier spring on the lower end of that valve(the spring that you need to take out that tiny pin to get apart) to get more pressure easier than redesigning the linkage. They changed the valve and springs on larger tractors to accomodate a lock nut and increase the pressure to 235psi . Don't remember if they did that to 656 or not. Many are set higher of course as personal preference. I always liked to see the pto slip before it tore the center section out of clutch backing plate myself.

656 weak pto pressure

Yellott Canby

Member

Janicholson

Well-known Member

LarryT

Member

Yellott Canby

Member

the tractor vet

Well-known Member

pete 23

Well-known Member

Similar threads