A Different Approach to Transmission Kickdown

Christo

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Oct 4, 2019
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This post will be a bit controversial but I've decided to share something that has worked out great for me.

A common recommendation is to disconnect the transmission kickdown switch activated by flooring the accelerator because of the stress this places on the transmission. Some folks disagree, noting that it reduces the acceleration available in an emergency maneuver and it's easy enough to avoid flooring the accelerator when on a hill (I'm in this camp). In general, for hill climbing the recommendation is to manually downshift, but this can be challenging as well when under way. Because of the age of our coaches, the shifter is balky more often than not, and it's all too easy to miss Super (2nd gear) and to downshift into Low (1st gear). Talk about something stressful to both the transmission and the driver!

I decided that I wanted a way to manually activate the kickdown for moderate / short distance hill climb or acceleration situations. With this approach I could also let off the gas a bit to minimize stress on the transmission. The solution for me was to connect the kickdown switch to the unused cruise control activation button (a momentary switch) on the end of the turn signal stalk. I wired it in parallel to the accelerator-based kickdown and it works delightfully! I put a piece of heat shrink tubing over the black part of the turn signal stalk to avoid having a mislabeled button, and I attached a label describing the function to the inside of the glove box door just to be informative to potential future owners.

It is worth noting that that the kickdown uses different functionality in the transmission than manually downshifting. Functionally the downshift doesn't engage as strongly/positively. This can result in more slippage while engaging (which, by the way, reduces stress on the driveline if engaged under heavy load). It could also potentially permit slippage or additional heat under heavy load like a steep hill or when towing. In my case, though, under appropriate conditions, it provides a good boost while under way that is much less risky than trying to downshift via the column, and it's also preferable to lugging the engine.

Would love to hear your thoughts and comments.
 
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This post will be a bit controversial but I've decided to share something that has worked out great for me.

A common recommendation is to disconnect the transmission kickdown switch activated by flooring the accelerator because of the stress this places on the transmission. Some folks disagree, noting that it reduces the acceleration available in an emergency maneuver and it's easy enough to avoid flooring the accelerator when on a hill (I'm in this camp). In general, for hill climbing the recommendation is to manually downshift, but this can be challenging as well when under way. Because of the age of our coaches, the shifter is balky more often than not, and it's all too easy to miss Super (2nd gear) and to downshift into Low (1st gear). Talk about something stressful to both the transmission and the driver!

I decided that I wanted a way to manually activate the kickdown for moderate / short distance hill climb or acceleration situations. With this approach I could also let off the gas a bit to minimize stress on the transmission. The solution for me was to connect the kickdown switch to the unused cruise control activation button (a momentary switch) on the end of the turn signal stalk. I wired it in parallel to the accelerator-based kickdown and it works delightfully! I put a piece of heat shrink tubing over the black part of the turn signal stalk to avoid having a mislabeled button, and I attached a label describing the function to the inside of the glove box door just to be informative to potential future owners.

It is worth noting that that the kickdown uses different functionality in the transmission than manually downshifting. Functionally the downshift doesn't engage as strongly/positively. This can result in more slippage while engaging (which, by the way, reduces stress on the driveline if engaged under heavy load). It could also potentially permit slippage or additional heat under heavy load like a steep hill or when towing. In my case, though, under appropriate conditions, it provides a good boost while under way that is much less risky than trying to downshift via the column, and it's also preferable to lugging the engine.

Would love to hear your thoughts and comments.
No controversy from my direction. I think if someone understands all the implications, a mod like this is a fine idea.

The only thing I might do differently: print a black label with white text, affix it to the turn signal stalk, then maybe throw some of my clear shrink tubing over the top. Not sure how it would hold up as a thing that gets "handled", but I'd probably give it a shot.
 
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One other thought...
What's the current load on the original switch, and is the cruise switch up to the task? I overlooked this initially since I'm so used to working on cars with high-impedance digital discrete inputs running signals into their control modules. It's more likely that in this application, that switch powers a coil somewhere. The original cruise switch has some pretty small wires fished through the column. I can't recall the size. Worth a look, perhaps.
 
Christo I really like what you've done.

I wonder if a newer column shift handle might work. I haven't seen a GM equivalent but Ford part number 5C3Z-7210-AAA looks close. Other end would need to be spliced onto original - do that near the column so the weld isn't visible.
Ford 5C3Z-7210-AAA.webp
 
One other thought...
What's the current load on the original switch, and is the cruise switch up to the task? I overlooked this initially since I'm so used to working on cars with high-impedance digital discrete inputs running signals into their control modules. It's more likely that in this application, that switch powers a coil somewhere. The original cruise switch has some pretty small wires fished through the column. I can't recall the size. Worth a look, perhaps.
The current draw can't be much for the kickdown solenoid, but it's a fair question.