C120 61 auto problem

[barngem 3]

My automatic trans won't move on start up unless I move lever all the way and it will start suddenly. It also will disengage in reverse and I have to jam lever forward for it to engage again. Could this be the charge pump failing?

[squonk 39,020]

Could be lots of things. First thing I would do is look at all the linkage and the trans to tractor mounting plate.

[barngem 3]

I failed to mention that linkage is all ok and adjusted properly.

[daveoman1966 3,628]

The Sundstrand auto trans in these usually go bad gradually...due to hyd pump and / or hyd motor wearing out over time.  Your apparent 'sudden' power failure is more likely some other culprit.  It is very likely that the control lever mechanism has failed (broken parts? ).  Most often, it is a broken lock-down tab which allows the control mechanism to float free, without any control of it.  Look at the LEFT side of your hoodstand, as in this pic.

There MAY also be a cracked MOUNTING PLATE where the tractor frame is bolted to the auto trans. Here are 3 pics of how to repair that cracked frame plate.  Look under the tractor for this as this is a common point of failure. 

[barngem 3]

Thanks, didn't think of that however, checked and linkage is all intact.

[daveoman1966 3,628]

I had these exact symptoms you've described on a C-120 a few years ago.  As it turns out, the frame plate was cracked where it is bolted to the front of the trans...as I tried to show in the pics.  Crawl under your tractor and inspect this....very likely to be the problem. 

[barngem 3]

No issues with frame or welds, all good. Maybe I didn't explain my issue clearly enough. Start tractor up and can push trans lever either way and no tractor movement. "jam" forward and trans engages suddenly then works as long as I don't stop the tractor engine. Can have in reverse and sometimes will disengage, have to push lever forward quickly and will start working again. As if it looses oil prime. I was told the trans/sunstrand was overhauled before I purchased the tractor about 8 years ago, but has always done this, getting much worse now. I changed filter and oil again last year, no help.

[barngem 3]

• I am close to the point of locating someone like yourself that I can have look at it and attempt to get it repaired. I want to complete restoring but want it in good working order first.  I continue to work it some as my main lawn mower is a zero turn. I use it for rolling the yard and pulling wagon. I still have a "good" 42 inch mower deck I use to mow a small incline. Can you be of assistance on someone?

[daveoman1966 3,628]

I'm sure that, if I had your C-120 in my shop, it'd be easy enough to diagnose the problem.  However, we are about 300 miles distance...4 hours or more... making that impractical.  If the frame plate isn't cracked or loose, then it must be something amiss in the motion control linkage.  Pull the cover off of the tunnel housing and...with engine running... and back wheels  off the ground, move the motion control lever forward / backward and watch for loose or broken parts.  In doing so, take a few pics...or a video...and post them here. 

[daveoman1966 3,628]

Another thought.... you shift cam MAY be trashed.  With the cover off, watch to see how the NYLON slide (# 8)  moves UP and DOWN with the motion control lever movement Fwd or Rev.  I bet you find that it is cracked..OR that the Eccentric (# 7) is loose in the arm (# 6) as secured by the SHCS (#5).  It MAY also be that the slide (#8) is loose and wobbles about in the housing #4  

[squonk 39,020]

I had that little set screw # 5 loosen up once. Trans did all kinds of funky stuff. 

[barngem 3]

I have checked all the mechanical linkage, taken apart to check wear on #5,6,7,8 and all is good. Jacked up tractor and worked fine, but normal on first start up is when it doesn't work. Once working it, works fine most of the day until I shut it of  and sets awhile and except reverse will loose motion sometimes and then I have to move lever all the way forward for it to take hold again. FYI, I travel western PA for my work and you may not be out of the question for me to bring it to you sometime, if I don't figure this out. I don't think it is an external mechanical issue.

[daveoman1966 3,628]

When you put # 7 (eccentric) back into the arm (#6), make sure it is in the correct position and then LOCK IT DOWN with the SHCS # 5.

FURTHER THOUGHTS:....

There MAY be a broken spring or stuck valve(s) in the Hyd MOTOR section identified as parts # 6 thru 14 in this schematic.  You can open this valve port without pulling the entire hyd pump assy off of the tractor.  However...Thoroughly brush off any dirt / debris from the port plugs BEFORE you remove the plugs.  There is a plug on each side of the lower section of the hyd motor and you need to remove both of them.  NOTE...be CERTAIN to reinstall in EXACTLY the same position as removed.  Here are a couple pics to help.

Once again....KEEP THE ENTIRE AREA CLEAN...  In doing this, be prepared to replace the fluid...oil or ATF and install a new filter as well.

  

I meant to HIGHLITE parts # 6 thru 14 in this Excel SS, but it didn't work....  These are the concerned parts of the motor valves. 

 

MOTOR 90-1136, 37, 40.xlsx

Edited March 25, 2016 by daveoman1966
fix a file

[barngem 3]

All looks OK.

[daveoman1966 3,628]

There are tiny valves and springs inside each of the 'pistons'.  Be sure they are not plugged by cleaning with solvent and compressed air.

Are the side of the 'pistons' damaged or marred at all?

 

[daveoman1966 3,628]

I'm almost out of ideas, short of tearing down the hyd pump and motor.  Here are a few final thoughts:

1) Are you using an after-market drive belt?  The belt should be Wheelhorse Toro # 7478.  Most after-market belts do not share the same geometry of the OEM and will under-perform...at best. 

2) Do you also have the belt routed correctly?  There are guides on the back side of the belt cover to carry the belt in the correct path / route. 

3) Is the auto trans fluid discolored or smell burnt?   Is it at the correct level.....too much is as bad as too little.

4) Pull the belt cover and check the spring tension on the idler pulley. 

5) Do you have hyd lift for the mower deck or dozer blade and does it work consistently?

 

 

 

[barngem 3]

Its the OEM belt. I have always thought it was something internal, like sticking valve, broken spring, maybe loosing oil prime, don't know. I really appreciate your assistance and agree that checking all the "simpler" thinks to confirm is best. I am going to put all back together and use this spring for now. I don't want to go any further into this myself and realize you have the experience on these. I would like to contact you personally to see if you may work on this later this year if I brought it to you. Again, thanks for your suggestions.

[daveoman1966 3,628]

My trouble-shooting manual suggests the FWD or REV Check valves may be involved.  They are recessed and on either side of the hyd pump end cap as shown in this schematic.  There is another valve...the CHARGE VALVE that is lots easier to access and you should check it as well....in fact, check it first.  Once again....CLEAN EVERYTHIG THOUROUGHLY BEFORE POPING THESE VALVES OPEN.   

Edited March 28, 2016 by daveoman1966

[barngem 3]

There is no spring or cone in the charge valve behind the plug. There is one in the implement side but I don't use that. Could this have even worked with these missing? Can I use the implement spring and cone and leave the implement blank? I have not checked the reverse or forward as yet.

[daveoman1966 3,628]

 There should be a spring and ball valve (or cone) in the Charge Valve...behind the plug.  Take the parts from the IMPLEMENT valve port (since you don't use hyd lift) and transfer those to the CHARGE VALVE port...   See what happens.  I bet this will solved the problem. 

HOWEVER... you MAY hae the wrong spring in the implement valve...not sure.  Measure it and tell me the FREE length of it.

I have replacement springs.. 

[barngem 3]

exact one inch. Make me wonder since I was told this was overhauled before I bought it that they installed in the wrong port?

[daveoman1966 3,628]

Move that spring and valve to the front port...  bet that solves the issue.

[barngem 3]

Thanks, I will try that, I agree, I bet that's it. I will let you know. Thanks for your persistence and sticking with helping solve my issue.

[daveoman1966 3,628]

The guy doing the rebuild probably didn't know or forgot which port to put the spring and cone/ball valve in, especially if he didn't take pics or have notes to work from.  If your C-120 had an active hydraulic lift upgrade, the rear port would have a stiffer and shorter 3/4" spring and...usually...a shim pack to regulate the hyd lift pressure / force. 

I hope you've found the solution ... 

[barngem 3]

Haven't tried the repair yet as I have a broken steering casting I need to weld up. But got bit by the wheelhorse bug and just bought a B80 off ebay. I will use it while I restore the C120, then do the B80 next. Apparently the engine on the B80 needs overhauled first. I will update you on the final results later.