Sos woes

[sony224422]

I have been trying to get my SOS back together correctly. I had to remove/replace my control valve, as the one that was in it had been welded to. The cam Trunnion was welded to, to make the transmission shift with no cable. But was dangerous. With this set up I had 1st, 2nd 3rd 4th and 5th along with r2. I didn t try getting above those gears but I know r1 either didn t work or was weak.

I ended up replacing the valve, and checked all the plungers to make sure they were free. I adjusted the pressures per the manual up to 185 psi, and had it in all 3 test ports. I also adjusted the bands according to the manual.

Now I have 2nd sometimes, 3rd is the only one that will move the machine, and neutral in 5th, 6th and I think 9th. R2 works very slightly, almost like it s slipping. The other gears "hold" the tractor but don t really move it. I took the cover off and noticed the b1 plunger has oil leaking past it. I m assuming from the book this valve is shot too. I also think it might be leaking from between the halves, but I can t tell for sure. I tried tightening the bolts a little but didn t seem to change.

I did also mess with the bands again, I turned the 3 band in while in 5th and it will stop it from spinning. I don t think the bands are bad but I can t seem to get the gears back that I had. And the symptoms don t follow the book- so I am wondering if I m on the right track for the valve leaking is most likely. Hoping to have another to try soon. If that is the case that this one is bad, is there any way to repair them? Or is it not worth it? My original cannot go back in because it is cracked and the shift cam wobbles

 

[Bern]

Best I can make out based on your reports, you likely have a major leak in the direct drive clutch. If I'm
right, figure on a rear split and an almost complete teardown from the back end of the transmission.

To confirm my theory, drill and tap a cooler line banjo bolt for 1/8 pipe thread and tap in a 0-30 PSI
pressure gauge. Watch the gauge in the lube circuit as you shift through the gears. If the pressure drops
to zero or near zero in R1, 1, 2, 5, 6, & 9, you have confirmed the direct drive clutch problem.

Another way to confirm it is to take the control valve off and blow compressed air into the DDC/band 1
supply port, and compare what you hear versus doing the same with clutches 1-3. If you hear a massive rush
of air in the DDC pressure port, my theory is confirmed.

Since the second control valve has not brought you any significant changes, it's safe to say that the
control valve is not the problem here. And, it's completely normal to see oil escaping past the control
valve plungers, especially at the ends.

Check out the post linked at the end of this one. It covers some pressure testing I did with a laptop and
a video camera to try and make the pressure testing process a little easier to understand. There is a
video linked at the end of that post.

Hope this helps. Let me know if you have further questions.
SOS troubleshooting and video post from 2018

 

[sony224422]

Bern this is really good info. I think I need to elaborate more-it’s a 1964 but has a red transmission so I’m not sure it’s a direct drive either. when I first bought the tractor, it had forward gears and reverse (I can t remember which ones, but I also didn t go above 6th)

I know I had reverse, 1st, 2nd, 3rd, 4th and 5th. I don t know if they were operating correctly, but it did move in those gears. For sure 1st and 5th as I moved it around my yard. Reverse worked too as I backed up a hill. The shifter cam was welded to a ratchet to get it to work, it had no cable. I found this to be dangerous and I wanted to fix it right. When I tried to removed the ratchet part, the cam broke on one end. I removed this valve.

I put in a used valve that was freed up, and adjusted the pump pressure via the 3 ports and adjusting the screws. I got the trans warm enough and adjusted the bands, but I have seemed to not have any of the gears I did have. I took the cover off and shifted the cam manually, and I saw oil squirting out of the port on the right side if you re sitting on the machine looking straight down. I think that s the band 1 port. I also was not able to find a new gasket for the valve to the body of the transmission, they all seem sold out or on back order. I am wondering if I am not getting the proper pressure because it s blowing past the ports.

Will the test you offered show this?

This post was edited by sony224422 on 02/19/2023 at 04:43 pm.

 

[Bern]

Correction on the lube pressure gauge - better figure on a 0-100 PSI size. I see that I got up to 75 PSI during my test. It was likely pre-cooler side.

 

[Bern]

I'm wondering if you really knew which gears you were in when you had the original setup with the custom shifter. That's why I looked at your original post and concluded a likely DDC clutch failure, which is a pretty common problem with the SOS trans, especially the early ones.

I would do a lube pressure test like I suggested in my last post. Even though it's not mentioned in the troubleshooting section, testing lube pressure through the various gears is one of the most definitive and accurate ways to look for internal leaks. This is because the lube system is last in line for oil. If there's a leak upstream, the lube system suffers.

I can't help you with the gasket. I understand that all SOS parts are getting pretty rare. I have one apart myself right now, and I'm figuring I'll be busy with a scissors and a hole punch when I go to put it back together. I'd use anaerobic sealant if the internal end plays didn't factor in. Admittedly the control valve gasket would be a tough one for sure.

 

[Dieseltech]

The 871 and early 4000 SOS transmission I have, neither one has an oil cooler like my 6000 has to tap into.

 

[sony224422]

This is correct, I do not have a cooler. Is there another way to test this?

I am 100% sure I knew what gears I was in with the old shifter set up. I am wondering if I should take a video with the top cover off and post it.

A rear split would be miserable with the backhoe on it

 

[Bern]

No cooler complicates things for sure. And I really doubt that a video would be all that helpful with the
normal amount of oil that would be splashing around. You can try posting one, but I doubt it would be
conclusive.

Without a cooler circuit to look at, it all boils down to a healthy understanding of how the hydraulic
system works and making sense of the 3 different gauge needles bouncing around as you shift through the
gears. Hopefully the video I posted makes the system a little easier to understand. Even though I was
working on a 5000, the principles are pretty much the same.

 

[sony224422]

Bern when looking at the book, it doesn t say much about the lube circuit. Does it rely on something else?

Also, if I split the tractor, what should I be replacing as preventative maintenance

This post was edited by sony224422 on 02/21/2023 at 06:00 pm.

 

[Bern]

What do you mean, does it rely on something else? It still has a lube circuit, you just can't access it, at
least not very easily because it doesn't have cooler lines.

You *might* be able to access the cooler circuit at the back of the transmission, inside the rear axle
housing. If you pull off the plate that holds the traction disconnect lever and look inside, you should see
a switch screwed into the back of the transmission. Assuming you have enough room to reach your arm inside,
you *might* be able to unscrew that switch and insert a pressure gauge. Emphasis on the word *might*.

As for preventative maintenance, there really is none inside the SOS trans other than the filter.