Need Math (Geometry) Help With My Shift Linkage - 4L60E to Volvo 740 shifter

[lookforjoe]

So, I made a big mistake with my shifter pivot to reverse throw from the Volvo shifter to the GM transmission.
I was all pleased with myself for figuring out a way to incorporate the shift reaction rod (Volvo incorporated it into the shifter housing, it is needed to set where park aligns in the shifter gate) - shifter lever is forward of that in the photo.
The problem is that my geometry is weak, and I didn't factor that the Volvo lever shifts in an arc, so my fixed position upper hole does nothing , the shifter cannot move.
What I need has to allow for the shift lever to move through it's arc. My question is, can I just make and extended slot for the pin on the shifter lever to move through? If I do that I'm assuming the pivot arm would still push the lower rod back (or forward)? Does that make sense?
TIA

Lower linkage is great

 

[lookforjoe]

This is what I would do based on suggestions
I had the upper & lower holes about 32mm off the pivot. I don't know for sure if the gate spacing is the same, so I made the lower link rod adjustable so I can lengthen or shorten to adjust the throw. I have no idea how to determine the appropriate length of the slot, or if the slotted section should be on an angle instead of straight up
Thinking about this last night, I also realized I should probably use the center point of the shift lever as the starting travel point, so the arc either way would be less extreme - I'm assuming -

 

[DET17]

Retired engineer thinking out loud, whilst drinking morning coffee:

I would begin with the distance required for each gear increment from your GM gearbox. Once that is known, determine how far the OVLOV shifter rotates for notch it travels.

Draw the proposed linkage and solve for the pivot location. The angular arc traveled in degrees must be same..... but the actual arc length (S = R x Theta, where Theta is "radians" and R is the arc radius) must match each of your devices.

If these results are unsatisfactory, then toss the OVLOV shifter and buy a nice aftermarket that plays well with GM trans and make it look pretty.

Good luck!

 

[mikep]

I started to say some of that last night but made it too complicated. Thank you for taking the time to post that.
I got hung up on describing arc angles, but that is not the important part. The distances are the starting point.

 

[lookforjoe]

Thank you for taking the time to post what appears to be a very straightforward and concise description.
Unfortunately (for me) none of the math works for me without a visual object example

I'm assuming moving the pivot up or down would change the proportionate movement , so I made the lower rod adjustable to accommodate a possible difference in gate spacing GM vs. Volvo if I just center the pivot

It's the actuation of the shift lever arm that I can't visualize, the trans gate essentially travels in a horizontal line from there to the pivot arm, so I wasn't really concerned about mechanical linkage for that side of the equation.

What I'm unsure of is if the upper slot is simply a vertical channel with room for the shift lever pin to ride in, will it push the lower arm in the opposite direction to an equal degree if the pivot is centered.

Retired engineer thinking out loud, whilst drinking morning coffee:

I would begin with the distance required for each gear increment from your GM gearbox. Once that is known, determine how far the OVLOV shifter rotates for notch it travels.

Draw the proposed linkage and solve for the pivot location. The angular arc traveled in degrees must be same..... but the actual arc length (S = R x Theta, where Theta is "radians" and R is the arc radius) must match each of your devices.

If these results are unsatisfactory, then toss the OVLOV shifter and buy a nice aftermarket that plays well with GM trans and make it look pretty.

Good luck!

I started to say some of that last night but made it too complicated. Thank you for taking the time to post that.
I got hung up on describing arc angles, but that is not the important part. The distances are the starting point.

 

[mikep]

If you need to reverse the push-pull direction, instead of an additional linkage, try flipping the arm on the trans over as a starting point.
Visuals are great. Measurements are necessary.

 

[lookforjoe]

If you need to reverse the push-pull direction, instead of an additional linkage, try flipping the arm on the trans over as a starting point.
Visuals are great. Measurements are necessary.

Unfortunately I cannot flip the lever on a trans, there is no space due to the range switch that's above it. And the tunnel is in the way. So I have to figure out a way to deal

 

[volvomancharlie]

I also work better with visuals. Can you mock up the pivot piece in wood and play with the hole positions? I am thinking some paint stirring stick pieces would be sturdy enough-

 

[lookforjoe]

I also work better with visuals. Can you mock up the pivot piece in wood and play with the hole positions? I am thinking some paint stirring stick pieces would be sturdy enough-

It's easier for me to just make metal brackets, so I'll do that based on the sketches from Russell and see where it goes

 

[lookforjoe]

I forgot to wrap this up. I made a series of levers to transfer motion from the Volvo shift gate to the the 4l60E. Took some back and forth but it works and lines up with the shift gate

Reaction rod works properly to allow adjustments of the shifter/gate alignment up top

 

[cosbySweater]

A stock generic th400 cable works well too if for some reason you don’t like that setup.