Calling the SOS gurus...

[wp6529]

~65-66 4000 SOS, I think Super/major with all the options. PTO only working in ground speed mode. I finally got around to taking the trans cover off (in 105F heat) and find the PTO control linkage is ok and working fine with the new control handle I previously made.

Some more fiddling and I find the issue seems to be with the 540/1000 selector. I got it engaged and did a test with a brush hog which did fine until the speed selector seems to have slipped out of gear. I shut it down, fiddled some more and got it to engage again.

When engaged it seems to run smooth and with suitable power so I think the gears are ok and the issue is with the shift linkage. The manuals I have give a lot of detail on the drive sections of the SOS but almost no detail on the PTO speed selector linkage and mechanism.

It seems the is not much accessible without splitting, which sucks since I have plenty of tools but am severely lacking on shop space to fit a tractor in.

Thoughts on likely issues, anything accessible without splitting, etc?

Thanks,

Pete C.

 

[Bern]

I just happen to have one of those transmissions apart right now, so I hope the photos are of some help.

The first pic shows some of the parts mocked into the front of the case. I left the forward drive gear off of the input
shaft so you can see the shift fork more clearly.

The second pic shows the input shaft and the two drive gears, along with the shifter mechanism exactly as they would be
installed in the case.

The third pic shows an exploded view of the shifter mechanism. Note the very narrow machined slot that holds the external
handle (in blue) to the internal shaft. Make sure the bolt that holds them together is tight, maybe it came loose.

If the problem is internal (say, a broken shift fork or sheared clevis pin), you should be able to remove both of those
parts through the front cover opening after splitting the tractor behind the engine. It's not a bad job, better than
disassembling the entire trans, which you'd have to do if you wanted to remove the PTO clutch pack itself. Just MAKE SURE
that the input shaft stays put when you pull the front cover off. If the shaft comes out with the cover, that will make for
a bad day.

 

[wp6529]

Beautiful, very clear. I'll look at it further tomorrow and start planning the split if necessary.

Thanks!

 

[Bern]

Let us know what you find, because I'm curious as to what happened here.

 

[wp6529]

First check - The operating lever is connected securely. No damage to the slot on the lever or the flats on the shaft.

Is there any way to get an inspection camera into the area to view the shift arm and fork? I have a nice small 3.9mm one, but I'm not seeing a way into the area short of drilling a hole and then tapping for a plug.

From the feel of it, I'm suspecting the pin may have come out and the shift arm is just moving on friction.

This post was edited by wp6529 on 08/21/2023 at 07:08 am.

 

[Bern]

About the only way of getting a camera in there short of drilling a hole would be to remove the steering box, which is not a
fun proposition just for the sake of inspection.

Will the handle rotate farther than the 3 slots in the case? In other words, could you rotate it say 180 degrees or so? If you
can, you either have a sheared or missing pin, which you won't be able to access through the steering box hole. Instead you'll
need to split the tractor behind the engine and come at it from the front.

 

[wp6529]

It will rotate somewhat past the three holes, but not 180, probably about 90 degrees overall.

 

[Bern]

Something is wrong inside then. It shouldnt rotate much either side
of the arc of the 3 holes, because the shift collar should be limiting
the travel internally, as I hope you can tell from the pics I sent
yesterday.

Im guessing the pin is partially sheared. If the pin had fallen out it
would spin until the outside lever hit the case.