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Sundstrand Hydro/Trans Mind Of It's Own


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#1 Billy M ONLINE  

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Posted September 14, 2015 - 10:37 AM

I picked up an S-16-H over the weekend.  The tractor is in very good shape with a newer 42" mower deck.  The K341 runs great, deck is quiet, but the hydo/trans is bad.  I knew this going in.  I'm debating whether to tear into the hydro and fix it, drop one of my spare hydros in it, or part it out (for me).

 

What it does...

It goes forwards and backwards, full speed only (in reverse also!).  It crawls to speed and then goes full speed, irregardless of lever position.  Once at full speed in either direction it won't stop or return to neutral.  I can move the control lever, and it will occasionally slow for a split second, then back to full speed in whatever direction you are going.  You can shut it off and restart it, and it will be in neutral if the lever is put there from starting.  Sometimes it will go from fwd to rev while moving fwd, with the lever still in the fwd position.  That is really fun, going from full speed fwd, to full speed rev!  I can move the fwd/rev lever back and forth while moving and nothing but split-second slowing happens.

 

So...has anyone had this happen to them or fixed a hydro with this issue?  I've never torn into one of these and was wondering if it took a nice pile of money to rebuild one?  I have a spare hydro for an easy fix, but I'm all for learning something new with a rebuild.  I read the Sundstrand rebuild article on here and don't think I would have a problem doing it.  I just don't want to spend a bunch of money on it when I have two spares sitting on the shelf.

 

Thoughts, suggestions??

 

Thanks in advance.

 

Billy



#2 48willys ONLINE  

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Posted September 14, 2015 - 12:13 PM

I really don't know anything about the ariens tractors, it is a an odd problem. But with my little experience with the sundstrand units  I'm not sure how it could be in the pump. Did you go over the control linkage and make sure everything is tight and/or moving freely?


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#3 Billy M ONLINE  

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Posted September 14, 2015 - 12:18 PM

Yes, linkage is fine (no play, moves freely).  The guy I bought it from took it to a shop.  They told him the hydro needed rebuilt.  The pump works fine, as it drives fine with plenty of power when it does drive, and the hydraulic lift still moves quick and smooth as it should.  The shop he took it to quoted him $1K to rebuild.



#4 olcowhand ONLINE  

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Posted September 14, 2015 - 12:26 PM

The roll pins in the rockshaft are broken.  Just the friction of the shaft through the plate that the pistons rub is all that is moving the plate, and once the force goes against the plate from the pistons, it forces them to full tilt/full speed.  Roll pin length is very critical when replacing.  There are 2 roll pins each side.  If you replaced them with a single roll pin equal in length to the 2 OE pins, it's impossible to get them out if you should ever need to get back into it later.


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#5 olcowhand ONLINE  

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Posted September 14, 2015 - 12:29 PM

They are standard diameter pins, so if the ones in it are broken or slipped out of place, you can cut a longer pin to the correct length instead of going to a dealer.  In rare cases, the pins slip out of place, but even if they are intact but out of place, put new in.


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#6 1964Deere OFFLINE  

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Posted September 14, 2015 - 12:39 PM

Could also have a stick plunger in the hydro release. I'm agreeing with olcowhand, but have seen where one of the plungers gets stuck and it does the same thing

#7 Billy M ONLINE  

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Posted September 14, 2015 - 01:03 PM

Could also have a stick plunger in the hydro release. I'm agreeing with olcowhand, but have seen where one of the plungers gets stuck and it does the same thing

I've had a stuck plunger before.  For me, It has always resulted in a loss of fwd or rev, depending on what plunger was stuck.

 

Also, I did check the plungers.  They were depressed with the transport lever to roll/load the tractor on my trailer.  I flipped the lever to test and both plungers came back up.  I even pulled up on them to make sure they were all the way up.



#8 Billy M ONLINE  

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Posted September 14, 2015 - 01:22 PM

The roll pins in the rockshaft are broken.  Just the friction of the shaft through the plate that the pistons rub is all that is moving the plate, and once the force goes against the plate from the pistons, it forces them to full tilt/full speed.  Roll pin length is very critical when replacing.  There are 2 roll pins each side.  If you replaced them with a single roll pin equal in length to the 2 OE pins, it's impossible to get them out if you should ever need to get back into it later.

That makes perfect sense.  Hopefully it's that simple.  That would definitely be worth fixing.  5/8" was the critical roll pin length according to the how-to article on this site.  When I tear it down, I'll resurface everything I can and get it back in good working order.  I just cleaned off my stainless steel workbench a couple weeks ago.  I guess I have a task for it now!



#9 artbuc OFFLINE  

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Posted September 14, 2015 - 01:37 PM

Billy M, could you post a link to the Sundstrand article? Thanks.

Edited by artbuc, September 14, 2015 - 01:37 PM.


#10 Billy M ONLINE  

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Posted September 14, 2015 - 01:55 PM

Billy M, could you post a link to the Sundstrand article? Thanks.

http://gardentractor...or-rebuild-r147



#11 Billy M ONLINE  

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Posted April 11, 2016 - 09:33 AM

That was it!  The roll pin on the control lever was sheared.  I had a roll pin in my bin-o-roll pins, so I didn't have to get any parts.  I also replaced the rubber gas tank bushing and put a new fuel line & filter on while the tank was out.  I also replaced a suspect hydraulic line to the rear lift cylinder with a used one I had in my parts bin.  That's a much easier task while the fuel tank is already out.

 

Olcowhand...I'm curious.  Is using 2 pins recommended for replacing the pins with the hydro unit in the tractor?  I pulled the hydro unit to inspect/fix it (not a difficult task).  I used one roll pin to fix it.  It was a piece of cake with the hydro unit out.  There was plenty of room to punch the pin in/out.  I etched a line across the end of the shaft for future reference of the hole location through the shaft.

 

Also...that's a pretty hefty roll pin.  Does the feedback from the swash plate actually have enough force to shear that?  If so, that's pretty impressive.  One would have to be working the tractor pretty hard to shear that.


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