Branson 4220 PTO shifter grinds

defranks · Oct 24, 2020

My Branson 4220 has just developed a problem, or at least I just noticed it. The gearbox grinds hard when I try to shift the PTO into the 1000 rpm position, hard enough that I cannot get it to engage. It shifts normally into the 540 rpm position, though. When I shut the engine off the shifter moves freely from neutral to 540 and to 1000. I'm pretty certain that the shifter fork is moving normally, as I can feel the detents. And if it wasn't moving, then the gears wouldn't grind.

So it appears to me that the shift mechanism itself is fine, I can feel the PTO moving into the 540 and 1000 rpm positions when the engine doesn't run.
The clutch is disengaging the PTO correctly. I can shift into 540 just fine, and when I'm powering an implement the clutch engages and disengages the PTO output as expected.

Any ideas what the problem might be? I haven't had the PTO in the 1000 rpm position in a very long time, I just happened to try to shift it there and discovered the problem.

I'm considering disconnecting the switch that prevents starting the engine with the PTO in gear, putting the PTO into the 1000 rpm position, then starting the tractor with it in gear. I assume that's purely a safety factor and that no harm will come to my tractor if I do that.

ericm979 · Oct 24, 2020

My 3725 will start with the PTO in gear. I don't know if it will start with the PTO clutch engaged (switch on). I have not tried that.

If the PTO clutch is disengaging properly the PTO gears should not be turning signficant force. They're straight cut with no synchros so they're not going to like being shifted under a load.

If the 1000 rpm gear set has been damaged, like maybe it was shifted when the PTO was engaged, then it would be harder to get the gears to mesh, making it want to grind more.

defranks · Oct 24, 2020

Thanks for your input, Eric. I think my tractor is a bit different from yours. No switch for the PTO, just a shifter and manual clutch. The clutch is dual-stage, the first bit engages the PTO and the rest of the travel engages the transmission, if it's in gear.

The 1000 rpm gear set hasn't ever been used, I don't think, beyond just trying it out to see that it works. I normally use the 540 rpm set for running my chipper or brush hog.

I looking at the manual it appears that the PTO gears are the constant-mesh variety with a fork that moves a selector from one gear to the other. I doubtful that the gears are damaged, but think that the shifter dogs may be stuck, somehow.

K5lwq · Oct 24, 2020

I would temporarily bypass the safety switch and test as you suggested. That would tell you if anything is wrong with the gears or if the clutch is just a little out of adjustment. There should be no difference between the tractor being off or clutch pushed all the way down.

ericm979 · Oct 25, 2020

With constant mesh gears the dogs can get hammered by shifting under power. It's common in motorcycle transmissions.

I'd think that the 540 gear set would also grind if the clutch was not fully releasing.

If you have to you can remove the top rear cover on the trans to inspect the gears. At least on my 3725, I'm assuming yours is similar there.

K5lwq · Oct 25, 2020

My question is why is anything turning to grind a gear if the clutch is fully released? Two stage clutches can be tricky on getting the adjustments correct.

I would think the 540 could fall in because of wear with use. The 1000 has not been used so that might explain the difference. I really have no other explanation but would be where I would start. :confused3:

defranks · Oct 25, 2020

I disconnected the safety switch and started the tractor in gear. The PTO turned correctly, and shifted correctly. Actually the first time back to 1000 rpm it ground just a little bit, but not at all after. Go figure.

I'm real familiar with motorcycle transmissions, and I think the PTO works about the same way. And even with the clutch fully disengage, the PTO shaft turns, but not with power. So maybe I do need to adjust the clutch a bit, but as I mentioned, 540 was never a problem. Honestly, I'm pretty much stumped, but what the heck, the PTO transmission is working correctly now so I'm happy. I think I just need to put the PTO into each rpm setting every time I run the tractor, or at least once a month or so.

I bought the tractor new, and it's never had the PTO shifted under power. Always while stationary and at idle with the clutch disengaged.

Thanks for the input, guys.

K5lwq · Oct 25, 2020

Great news! Glad it is working now. Probably will be fine with a little use.

bernardcuziillo · Oct 30, 2020

defranks,
I think your linkage needs adjusting. The hand lever is connected to a series of parts that eventually move a fork that slides a sleeve gear from one of three positions: High speed, neutral in the middle position, and low speed. If the adjustment is too far in one direction, neutral and one gear work fine, but the other gear only barely engages, and thus grinds. I've done all this on my 2011 4520R. The adjustment is near the hand lever below a sheet metal cover or two. It's just jam nuts and turnbuckle type rods. Get the manual on this site if you need more details. I put a photo from the manual below.

I also don't like the sound of the safety being disconnected. Also, it's just much more convenience to not have to stop and start the engine every time you need the PTO engaged. That kind of inconvenience will temp you to do things that put you at hazard.

Edit: Also, even though it's not grinding after starting with it engaged, the contact area between the two gears is much smaller that it's supposed to be. This could result in early wear out, possibly cascading into bigger problems in the gear case due to all the hardened steel debris generated in the first failure.