SOS Trans Work

jaluhn

Member
How much of a PIA is it to work on one of these? How many special tools required?

The unit in my backhoe (65(?) 3500) seems to have a broken or disconnected forward band - about 1/2 of the gears don't work. Those that do work seem to to work properly and there doesn't seem to be any other issues. However, having all of the gears working would be nice, and I can't imagine that having that band flopping around in there is doing much good.

The question though is how much of a pain is it likely to turn into trying to take the unit apart? I've done a lot of mechanical work and have a decent tool setup but haven't done much trans work.

Thanks,
~John
 
Before you touch that tranny or lay a wrench on it get a good shop manual that has complete coverage of the SOS. Be sure it has a troubleshooting section. Then find an experienced Ford tractor mechanic and pick his brain.
 
Get the manual, the trouble shooting section might very well tell you what's
wrong BEFORE you open it up. Seems what gears do and don't work can give you a
pretty good idea what band or clutch in not at muster. As an early powershift
transmission they are complex and can be finicky, Ford took two tries to get them
right. The manual might very well give you a fair idea of what's in store for you
if you decide to attempt repair so at least you get to peek before you commit
yourself to possibly breaking your tractor for good or having to commit to a
trans swap or carry it to a repair shop in boxes with a really dumb look on your
face.
 

Don't think you can say for certain you've got a broken band flopping around in there. Half the gears would indicate to me that it has direct drive clutch or B1 problems. These could either be mechanical issues or hydraulic ones. Tell me which ratios work and which don't and I'll say more.
 
I have the manual and have read the manual.

The picking an experienced mechanic's brain part is what I'm doing here.... :p

Troubleshooting points to a defunct fwd band. Adjusting it does nothing and there doesn't seem to be any tension on the adjuster even screwed all the way in. I also have an intermittent rubbing/scraping noise from the forward end of the trans.

My conclusion is that either than band is broken or the link between band & adjusting screw or band and piston either broke or fell out. I think there's a decent chance the actual fix will be pretty easy, it's a question of how badly am I likely to screw something else up getting there, or find that the rest of the unit is so screwed up it turns into a huge mess.

The tractor has 4000 hrs indicated though I am unsure how accurate this is. It looks to be in good enough shape that they may be accurate. I serviced the trans, changed the filter and cleaned the screen and didn't see any evidence of major wear or problems so I think the unit is in good shape aside from the fwd band issue.
 

Dean,

Off the top of my head I do not recall exactly - I know R1 and about half the fwd gears, including 7 & 8 IIRC don't work. I do know that when we looked at the list and compared to the manual the commonality were that they all had the fwd band engaged.

On all of the malfunctioning gears, the tractor moves, but has little power.

I believe that I checked the hydraulic pressures on the trans and they were all within spec although I cannot exactly for sure.

The telling things to me are:
1) The failed gears all have fwd band applied in common
2) Failed gears seem partially working as if something is not completely applied or slipping
3) The fwd band adjustment has no resistance even screwed all the way in.
 
Not sure what you're calling the forward band. In SOS nomenclature, there is no such thing. There is Band 1, Band 2 and Band3.

Band 1 would be applied in half the ratios, to wit: R2, 3,4,7,8&10. In this scenario the direct drive clutch is released and the transmission is in an overdrive mode. If any of these ratios are functioning, B1 is not your problem.

R1 is a direct drive ratio whereas 7 & 8 are not. I'm guessing your memory on which ratios malfunction is not good and that you need to recheck it if you want good mechanical wisdom from us.
 

You are right, my memory is likely faulty as to which parts are which.

I am not asking for help troubleshooting as it has been established to my satisfaction that the forward most band (B1?) in the transmission is not applying and it is almost certainly due to a mechanical issue in the band or linkage. I believe this was concluded with help from this board.

My question is that assuming that the troubleshooting is correct, how likely am I to be opening a huge can of worms by trying the open this thing up to replace / repair the band? Based on the manual I think I can fairly easily pull the main parts out of the case to access the band, repair it and put it back together.... but I also know that what looks easy and straightforward in the book may or may not be that way in practice - hence asking for thoughts from those more experienced than myself.

That list of ratios posted does seem to match the ones I have that don't work.
 

At the moment neither the tractor or any of my manuals are readily accessible to me, hence the reliance on memory - I'm in the middle of moving, however I do have the time to research and plan what work I need to get done when I do again get a good place to tear stuff apart. This is why I don't have clearer more accurate info to post.

Thanks!
 
Fair enough but I would not even think about opening it up without complete diagnosis.

As I said earlier, it could be a simple external fix but it is necessary to know what ratios are not functioning to diagnose.

Dean
 

Oh, of course. Had my share of problems that could have been fixed a much easier way to jump into major work without being sure. :lol:

I am 95% sure that list is correct for the ratios that are not working, and I recall narrowing it down with high confidence to a mechanical problem in that band - including testing hydraulic pressure to the servo IIRC.
 
Hello John , If Band #1 is the problem you should be able to remove the steering box and look inside to see if the link fell out from the adjusting screw if it did you can drain the oil pull the link out of the bottom of the trans reinstall it then readjust the band and hopefully that will be it . I have done it with the 4 cylinder tractors but never had to do it with a three cylinder tractor but the opening should be about the same size . I have a three cylinder trans. here but not in the shop it is out covered up and buried in the snow about 2 or more feet of wet heavy snow now , if I can dig it out I will take a look at it to see how much room to work it has . Thanks Tony
 

That, Sir, is a most excellent idea! Thank you! :D

Even if it's tight to work in there it's at least going to help id where exactly the issue is and hopefully it can be fixed - I'm used to working in small spaces.
 
You have gotten a lot of good advice on this. I have two good
working (3 cyl SOS trans) here for the 3000. Looking in the
top, I would be hard pressed to replace the strut or the band
on B1 thru that opening, but it may be possible after removing
the control valve body. Possible that it is not just one problem.
BUt you stated no tension on the adjusting screw for B1, so
that is definitely an issue. No real special tools needed, but it's
a three-way split and all parts removed from rear of unit. Just
make sure all thrust washers are installed in the exact reverse
order they were removed. Should you need to replace it let me
know.
 
Tequila, Tony's suggestion was to remove the steering box and go in through that opening, not the regular top cover of the trans where the control and PTO cables go through.
 
Dean, your right, and so was Tony. This AM it was kinda dark
and cold in the barn, tranny on end and me old. Lots of
excuses. I just took a second look in much better conditions,
better light. Sorry John, it still would be difficult but the strut is
right there in sight, just not much room for fingers. Of course
mine has both covers off already, and without the valve body
you could get two hands in. Also you could make sure the
band is intact. Again I apologize, this sight and most people on
it are so helpful I hate to muddy the water.
 
Finally got around to doing this and it turned out to be very easy to do after removing the steering box. Not too much room true, but enough to get in there easily and get a replacement strut in. Wound up also replacing the band since the old one was badly worn and I had gotten a good used one just in case. Had to bend it a bit to get the old one out and new in, which undoubtedly wasn't good for it, but it seems to work. Nice to actually have a 10x2 trans instead of an awkward 5x1.... Also rebuilt the steering ram (was leaking horribly from the cylinder packing) so it's really nice now... functioning power steering and a good transmission!
 

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