Toro Wheel Horse GT 550 Slow in High Gear

[Pattyb 18]

Good morning,

I am hoping someone can help me because tractor repair is not my area of expertise but I can research, read and follow directions.

 

I bought this tractor about a year ago and it does not achieve full speed, full throttle-high gear speed is the same as low gear, but it flies in reverse. It has 500 hours and I changed the oil and filter, I didn’t clean the power steering filter because all of the posts that I’ve found, this is never the solution. We disconnected the smart steer in the spring using a method found on this site but that didn’t help; it only prevented it from slowing down more while turning and that’s a good thing.
 

Today my husband is going to help me check all the pivots and linkages but like I said, I can research and read and think the problem lies in the neutral adjustment. I was just looking at the 5XI SERIES TRACTOR HYDRAULIC SYSTEMS SERVICE MANUAL and saw a note about the pivot point and went to look at mine, the machine is not running and the pivot point look like it is facing the wrong direction. My questions are, am I correct that when you don’t have any pressure on the accelerator the pivot should be facing the other way? Can I change this while the tractor isn’t running? I realize that we should do it while it’s running to avoid creep but I took it apart so that I could clearly see everything. I am trying to avoid guessing and making it worse, that’s why I came here. Finally, since it’s apart, is there anything else that we should inspect?

 

Thank you in advance for helping a novice.

[953 nut 69,954]

I am not very knowledgeable on the newer Wheel Horses but some of our members like @Pullstart or @JoeM may know the answer.

[Handy Don 17,606]

I’ll offer some basic orientation that might, I hope, help you with diagnostics. 😁

 

The blue arrow points to the base of the input control arm on the hydro. It rotates when movement of the plate (yellow arrow) applies force against the eccentric (red arrow). The plate’s movement comes via a linkage to the forward/reverse motion control lever you operate by hand. 

 

The hydro pump/motor is internally symmetric making it capable of the same output speed in either direction. Moving the hydro’s input arm in one direction yields forward and the other way yields reverse. HOWEVER, those clever WH engineers shaped the slot in the plate so that (when correctly adjusted) it pushes the eccentric further in the forward direction that the reverse direction--hence the normal difference between full forward and full reverse. (Other parts of the linkage are also involved.) There are several possible reasons for having insufficient arm rotation in your “forward” direction. ONE of the reasons is addressed in Step 6, above. 

 

Over time, the sides of the slot in the plate and the sides of the eccentric can wear down through normal use leaving the eccentric “loose” in the slot. Step 6 in the manual is showing how to rotate the eccentric where it is attached to the input arm to where it is slightly narrower than the slot in the plate (to permit free movement with minimal slack) and where the end of the input arm (i.e. the bolt) is positioned in the middle of the slot. Further, it wants the “notch” in the eccentric to be pointed away from the input arm’s base at the hydro--yours is toward. Some subtle geometry dictates this.

 

So your first step (with the engine off) is to hold the hex part of the eccentric with one wrench while loosening the bolt that holds it with a second wrench (or socket). Carefully rotate the eccentric 180º from pointing ESE (east southeast in the picture) so that it points WNW (west northwest). Retighten the holding bolt while again holding the eccentric. 

 

This might have some effect on the forward speed, but likely not a lot!

Other adjustments to the linkage are likely needed to make sure that when the manual motion control lever is firmly in neutral the input arm to the hydro is centered (i.e. the tractor isn’t creeping forward or backward) and that the full range of motion control input is being transmitted to get proper rotation of the input arm.

Here, though, we reach the limit of my expertise as I’ve not worked on this model. I will note that the Eaton manual for the 1100 has pretty clear instructions for adjusting the linkages so I would continue there first and, of course, come back here with questions (and pictures!)

 

Edited 1 hour ago by Handy Don

[oliver2-44 11,788]

The slot shows wear on the middle left side above the eccentric.  Make sure the edges of this wear area are smooth, use a file and emery cloth to remove any metal burrs.

While this is probable not you mane problem, it can contribute to rough movement.