3-Point Hitch Which Top Link Hole to Use - an illustrative model

[pmbutter]

There is a lot of contradictory information about which hole to use for the tractor end of the top link. It's confounded by the issue of hydraulic draft control, which some tractors have, as the effect of that draft control is more pronounced at certain holes.

I know the best advice is to RTFM, but my manual (LS R4047) didn't have any info on the subject.

Because I found the geometries hard to visualize, I built myself a little model. It was an amusing diversion, and was fun thinking about Harry Furguson's groundbreaking invention... which originally had two links on the top and one on the bottom. Who knew?! 3 point linkage.* 3 point tractor linkage

There will be some variation from tractor to tractor about where the connection points are relative to each other, but you may find looking at these pictures helps you think about your tractor.

The bottom hole provides the greatest elevation change of the "tail wheel" of my "implement", but it also the greatest angular change relative to the plane of the ground.

The top hole gives the least elevation change of the tail wheel, but better maintains parallelism with the ground.

Hence, I'm thinking the bottom hole is best for something like a landscape rake where you might want to lift it up and out of the way, perhaps with a little more angle so trash drops off the tines.
And a plow ought to be in one of the upper holes, so it's still at a proper working angle, regardless of its depth.

Happy Spring, everyone!

 

[Ford850]

There is a lot of contradictory information about which hole to use for the tractor end of the top link. It's confounded by the issue of hydraulic draft control, which some tractors have, as the effect of that draft control is more pronounced at certain holes.

I know the best advice is to RTFM, but my manual (LS R4047) didn't have any info on the subject.

Because I found the geometries hard to visualize, I built myself a little model. It was an amusing diversion, and was fun thinking about Harry Furguson's groundbreaking invention... which originally had two links on the top and one on the bottom. Who knew?! 3 point linkage.* 3 point tractor linkage

There will be some variation from tractor to tractor about where the connection points are relative to each other, but you may find looking at these pictures helps you think about your tractor.

The bottom hole provides the greatest elevation change of the "tail wheel" of my "implement", but it also the greatest angular change relative to the plane of the ground.

The top hole gives the least elevation change of the tail wheel, but better maintains parallelism with the ground.

Hence, I'm thinking the top hole is best for something like a landscape rake where you might want to lift it up and out of the way, perhaps with a little more angle so trash drops off the tines.
And a plow ought to be in one of the lower holes, so it's still at a proper working angle, regardless of its depth.

Happy Spring, everyone!


View attachment 596427View attachment 596428View attachment 596429View attachment 596430

Doesn't that contradict what your test revealed?

 

[Reb954]

Interesting demonstration.

I don't use any implements that require draft control so I don't know much about how it works. When mounting my snowblower and mower I just make sure the top and bottom links are as close to parallel to each other as the existing holes in the tractor and implement allow.

 

[pmbutter]

Yep. Had a senior moment there. Editing to correct. Thanks, Ford850.

 

[oosik]

My tractor has three top link holes. #1 being on top - #3 being on the bottom. This is the page out of my Op Manual that details which hole to use. I currently have my hydraulic top link in the middle( #2 ) hole.

View attachment 596448

 

[Farmer495]

Nice diagrams.

 

[Wayoldguy]

Thank you! I have been trying to picture that in my head for years. Now it makes sense!

 

[Texasmark]

Thanks for the post. I just bought a drum mower and the non-mowing "stow" position is directly behind the tractor. Since total length out behind where the rear tires contact the ground is like 9', having adequate ground clearance is important. I had thought about doing a diagram such as yours to determine which hole is best....you saved me the effort.....on setting the implement down using the lowest hole, the height of the 3 pt when mower is on the ground makes for a straight line....other things like a tandem disc could be as shown in the 4th picture.

On Draft control, my 3910 manual specifies that the lower hole is for the fastest response....didn't explain what you did.

 

[CobyRupert]

Thanks for the post. I consider myself having 1/2 a brain, and it would always hurt when trying to work through what your model easily shows.

Couple of question/notes:

Don't these models really show what adjustments can be made if you've reached the limits of adjusting your top link and want a "little more"?

I believe the primary reason for having the three holes is to adjust sensitivity of draft control as Texasmark and Oosik refer to. However, I believe the 3 holes are usually on a bracket that is a "lever arm" itself, as part of the draft control sensing. So whether the top hole or bottom hole is more sensitive and has most draft control response, depends on whether the "fulcrum" (and the attachment of this bracket to the draft control "sensor") is at the top or bottom of this bracket (if that makes sense). Other may know better than me, but which hole is most sensitive may differ from tractor to tractor based on how the draft control input linkage is oriented.
:2cents:

 

[oosik]

I'll be honest. That page I posted out of my Op Manual makes no logical sense to me. The really sad part - there is little to no verbal explanation to go along with that page. pmbutter's posts make a lot more sense. I think the page I posted has more to do with draft control. Not really so much - what hole to use for the top link.