Tractor Lunging Unexpectedly!! Scary!! Help please!

[heysavoy 22]

I have a 1990 wheel horse classic model # 31-12KE01 with a hydrostatic transmission. I've noticed recently when I put it in reverse, it seems to hesitate to want to go backward. I also found I needed to keep my hand on the gear or it would sometimes abruptly stop. Today I had a scary experience when it lunged unexpectedly to the point the front tires came completely off the ground and almost flipped me over backwards. I took the middle plate off at the gear shift (see picture below) trying to figure out what was wrong and didn't see anything that looked out of order but honestly I don't know what I am even looking for. When I've had other problems, my only saving grace has been this forum which has always been there to help me when I needed it. And I really need some help now because I'm in the middle of leaf season with over an acre of yard and 25 hardwoods. I live in the Charlotte NC area but don't know anyone who works on a wheelhouse especially a 1990. Thanks in advance for any help someone could offer. I love my old tractor and was hoping it would last me another 10 years. 

 

[Ed Kennell 43,539]

Check the cam plate and linkage under the seat.

[WHX?? 53,121]

...then give it a bath and lube job. That kind of dirt build up can wear away pivot points quickly not to mention plugging cooling fins.

Remove the fender pan and clean thoroughly. Inspect & adjust per the manual. 

Cleanliness goes double for hydros. 

[heysavoy 22]

Thanks for the quick reply. Much appreciated. So I assume I have to remove the seat to do so? Told you I didn't have any idea what I was doing? 

Edited November 15 by heysavoy

[gwest_ca-(File Mod) 11,815]

 

[c-series don 10,750]

Yes, the seat and the fender pan in order to give the hydro unit cooling fins a proper cleaning. Compressed air works best. Adjusting the cam plate for the motion control should be in our manuals section. 
 As soon I posted this so did @gwest_ca ! 

Edited November 15 by c-series don

[oliver2-44 11,036]

Go through the manual and note some of the hydro linkage gets lubed and some linkage needs to be dry

[wallfish 18,722]

Could that lurching also be caused by a worn hub key way?

Take a marker or chalk and draw lines on the hubs and axle faces, go in reverse and stop before going forward again. Look at the lines.

Go forward and stop, look at the lines. If the line doesn't stay true the entire time there is an issue with hub(s)

That could explain the reverse hesitation and if it popped up in forward after being in reverse.

[Bill D 2,425]

How many hours on the machine?  If it has high hours the cam and plate under the seat may be worn.  This will cause erratic operation. Had it happen on my GT1800.  Replacing the cam and plate fixed it.  Also check the heim joints on the linkage for play and replace if needed.

[Lee1977 7,439]

My 520-H did that in reverse when I got it.  As Bill said above worn cam and cam plate. The cam had a groove worn in it and would hang up, using enough force to move it put it way too far in the other direction.

Mine would go wide open in reverse, the only way to stop it was hit the brake. new cam and cam plate, I also added new 1/4" stainless steel heims j

 

 

 

 

 

 

 

 

 

 

 

 

Edited November 16 by Lee1977

[mae 59]

My transmission on a 314H was jerking me badly when I went into reverse or forward. Come to find out it was a bolt underneath the unit that had come loose. After tightening it is as good as new. I may not be understanding your issue exactly but thought I’d toss that out. 

[953 nut 62,798]

Take a look at the "F Plate" where the transaxle bolts to the frame. If it is cracked it will allow the transaxle (and that end of your shift linkage) to move around. It wouldn't take much movement to cause what you are experiencing. I have attached a picture of an F Plate. The cracks could be in the plate or where it is welded to the frame.

[peter lena 9,543]

@heysavoy  your  obvious lack of  MAINTIANCE  , is collectively  devouring  your unit , F/ PLATE  crack / stress . consol  collection of issues ?  wiring ?  difficult to  respond  , without  enhancing your frustration . maybe another member  , can address  this  more delicately  ,  wish you well ,pete  

[Handy Don 14,993]

Remember please, gents, the OP is a member with very, very little mechanical experience.

[Brockport Bill 2,108]

on 314h - I replaced the cam plate and some hardware that I was concerned was worn

[Brockport Bill 2,108]

5 hours ago, 953 nut said:

Take a look at the "F Plate" where the transaxle bolts to the frame. If it is cracked it will allow the transaxle (and that end of your shift linkage) to move around. It wouldn't take much movement to cause what you are experiencing. I have attached a picture of an F Plate. The cracks could be in the plate or where it is welded to the frame.

beware the tranny frame plate crack as noted 

[Ed Kennell 43,539]

21 hours ago, heysavoy said:

So I assume I have to remove the seat to do so?

To properly clean the cooling fins on the hydro...YES.

To inspect the cam plate and linkage for wear and proper functioning...NO.        Just flip the seat forward to access the cam plate thru the hole in the seat pan.

[heysavoy 22]

8 hours ago, peter lena said:

@heysavoy  your  obvious lack of  MAINTIANCE  , is collectively  devouring  your unit , F/ PLATE  crack / stress . consol  collection of issues ?  wiring ?  difficult to  respond  , without  enhancing your frustration . maybe another member  , can address  this  more delicately  ,  wish you well ,pete  

That's OK - at almost 70 yrs old delicacy is no longer as big of a deal. It's just hard to do the maintenance like I once did. 

[heysavoy 22]

6 hours ago, Handy Don said:

Remember please, gents, the OP is a member with very, very little mechanical experience.

You are correct sir but it's awfully satisfying when I can fix something. However .. this problem may not be "one of those".

[peter lena 9,543]

@heysavoy  can relate , next one is 80  for me , pete

[peter lena 9,543]

@Brockport Bill  that angular plate movement setting  is the issue , the related rod end only  moves in one direction , thats the problem , what you need is SMOOTH  ANGULAR DIRECTION , typically  adapted a HEIM JOINT   to  lever end , makes INCREMENTAL , ANGULAR  direction with total ease, also like SUPER LUBE HYDRAULIC OIL  for related fail safe operation .  nothing sarcastic , but  a simple  trials will show you the way . have regularly  eliminated a linkage / lever set up , with the  smooth / easy  direction of a heim joint  . also like that super lube , INSIDE EVERY RELATED CABLE , note the temp ranges . have also added  a coil spring assist to close  all my  cables , ? that way the spring is always helping you  in movement . do a lot of  intended movement  trials , every  end point / related , moves with ease . just a suggestion , pete 

[lynnmor 8,174]

16 hours ago, heysavoy said:

You are correct sir but it's awfully satisfying when I can fix something. However .. this problem may not be "one of those".

Get the tractor cleaned up, I use engine cleaner with a brush and a garden hose, change the transmission oil so we know it is correct (ask about that first), and then we can help you better.  These tractors are rather simple but the gang here will often give advice that sounds like it might be difficult.  One step at a time and the problem will be solved, if you have any questions about a particular item come back and get a clear answer because not every answer here will be correct.  We can't see it from here so photos are a big help.

[heysavoy 22]

Is it possible there is too much play in this bracket allowing the shift stick to jump between gears?

[lynnmor 8,174]

2 hours ago, heysavoy said:

Is it possible there is too much play in this bracket allowing the shift stick to jump between gears?

 

There are no gears, take that rear fender off and do the cleaning, then you will see that the cam plate moves the internals in a way that controls the speed and direction.  That cam plate has a friction adjustment so that it stays where you put it, that needs to be clean and dry, it is the only thing that should have no lubrication.  Often that needs to be disassembled, sanded and cleaned.

[heysavoy 22]

14 hours ago, lynnmor said:

There are no gears, take that rear fender off and do the cleaning, then you will see that the cam plate moves the internals in a way that controls the speed and direction.  That cam plate has a friction adjustment so that it stays where you put it, that needs to be clean and dry, it is the only thing that should have no lubrication.  Often that needs to be disassembled, sanded and cleaned.

Working on that now. I thought I remembered a flat - spring of some type that sat under the plate and pressed against the control lever is to keep the lever in position. But perhaps I'm wrong. Thanks