MF 165 PTO jumps out of gear

This message is a reply to an archived post by Walt in Iowa on November 16, 2010 The original subject was

"Re: MF 165 PTO jumps out of gear".

This is a continuation of a post dated 11-16-2010. My MF 165 tractor PTO would jump out of gear when running under load at engine speed with the posthole digger or brush cutter. It’s got the live PTO. I had to use a bungee cord to hold it in. The PTO problem first showed up after I had the hydraulic pump rebuilt including a new shaft. I finally solved the problem, and maybe this will help someone else. First some background. A spline on the end of the pump shaft drives the PTO in these tractors. The dealer who rebuilt the pump put in a new aftermarket shaft that had a different shape spline, and I thought that was the problem. So I switched to a new OEM pump shaft, installed new detent pin and detent spring, but none of that helped, it still jumped out. The machinery in the tractor is in good shape -- no obvious wear in the female spline, new pump dowels, all the bearings are tight, the PTO shift lever shaft has a good fit to the hole in the side cover, the pump shaft and PTO shaft are aligned properly, etc.

Finally I discovered the real problem. The spline in the sliding sleeve was engaging the pump shaft only about 1/8 of an inch. THAT'S ALL! As long as the original pump shaft was in the tractor, the problem did not show up, but when the pump was rebuilt with a new shaft, the wear pattern on the tips of the splines evidently no longer matched up, so the sleeve would get pushed off the shaft. Although the short engagement is enough to transfer power to the PTO shaft, it is obviously not normal, since the shaft spline is about 3/4" long. The tractor had always been that way. It must have been a defect from the time it was new in 1967 - possibly all the part tolerances stacked up the wrong way - and it finally showed up after the pump was rebuilt.

If you think you might have this this problem, you can measure your spline engagement this way: 1) Put the side cover on with only two bolts; 2) Shift the PTO to the engine drive position; 3) Carefully take the cover off without moving the sliding sleeve/gear; 4) Mark the shaft with a magic marker at the edge of the sleeve; 5) Slide the sleeve rearward away from the shaft; 6) Measure from the mark to the end of the shaft spline.

To get more spline engagement, the solution was to increase the travel in the PTO shifter. The PTO lever normally travels 10 degrees rearward when shifting to the engine speed position and 15 degrees forward when shifting to the ground speed position. I increased the travel to 15 degrees on the engine drive position, which gave me about 1/2" of spline engagement, and now the PTO doesn"t jump out. To do that, I had to modify the shifter fork in three ways. 1) Fill in the detent hole at the 10 degree position with weld and make a new one at 15 degrees, on the same radius as the other holes. I used a carbide drill because the steel is really tough and hard to drill. 2) Grind off some of the end stop, so the fork will travel far enough for the detent pin drop into the new hole. Do NOT grind the whole thing off. 3) I had to grind some off the side of the fork arm so the sliding gear doesn't hit the fork as it follows the fork forward. I ground on a 5 degree angle tangent to the fork pin and up the arm 2 1/2". That doesn't take away enough material to weaken the fork. I attached pictures of the modified fork.

Now the PTO stays in just fine, no more bungee cord holding the lever back. There was some work involved, but at least it can all be done through the side cover without taking the rest of the tractor apart.

Hi Walt,
Seem to remember your original posting on this problem Normally replacing the pump shaft and/or coupler will solve the problem. Difficult to believe that there was only 1/8" of engagement. How big was the gap behind the pump shaft to the front of the PTO shaft. It should be almost negligible as long as there is clearance.. Its a radical solution but good for you as it seems to have worked.
DavidP

Hi David,
I appreciate your reply. I know it seems strange that there was such little spline engagement, but it's really true. It was surprising to me too, but I was actually relieved to find this condition, because I had been pulling my hair out after eliminating all other possible causes I could think of. Where the two shafts come nose to nose there is not much gap, about 1/16" or so. When in ground drive, the gears lined up fine, but in engine drive the sleeve wouldn't come far enough forward, so I added more travel in the forward position. Having been around engineering and manufacturing for many years, I've seen how design and/or manufacturing mistakes can get out, and I'm convinced that's what happened here. From the parts book, apparently there were some changes to the main case on early tractors.

The PTO output shaft is located axially from the rear of the case, and the pump locates from the dowel holes in the sides, and since the two shafts meet properly, it seems the relationship between these is okay. But I've been suspecting that the side cover hole in the case may be mislocated, but in any instance, I'm thinking there is something dimensionally off in the relationship between the shift mechanism and the shafts. I'd guess my tractor probably isn't the only one with this issue, so I'm hoping my experience can save someone else some hair pulling. At least it's another thing to look for if the PTO won't stay in. Thanks, Walt

Hi Walt,
We could speculate for ever and a day on what differeces in spec might have caused the problem.
The main thing is that you have found it and rectified it without too much expense.

Cheers

DavidP