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Old 03-10-2005, 07:46 AM
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c6 downshift rod theory and practice

I need an explanation of how the downshift rod works (or is supposed to work) on a C6 trans. The 351/C6 I got from the bone yard had the rod broken off at the transmission lever (actually looks like some fool did it on purpose). It could even have a piece missing because my '32 pickup also has a C6 and the lever is in an upside down "U" shape while the lever pieces I have for my boneyard tranny would basically make a straight line. However, they are from two different years so the levers might be different.

I need to either weld up the pieces I have or fabricate another lever. However, I need to know exactly how the rod is supposed to operate in order to fab up the lever correctly. I've never actually seen one of these operate because you obviously can't watch it in action when your going 50 and you hit the throttle.

Here's my theory from looking at my "good" (running) C6...so please correct what's wrong with it or add vital data.

1) At speed, when pressing the accelerator to WOT, the downshift rod is pushed downward (toward the ground).

2) This downward motion of the rod is transferred to the downshift lever which rotates the shifter in a counter clockwise direction (is this correct?) tripping the tranny into the next lower gear.

If this much of the theory is correct I think I can weld up the lever at the transmission correctly. (Actually, I've already tack welded it in a position which assumes the above is correct...so I might have to undo what I have if it's incorrect.) But then, how much play should I have at the carb when the engine is at idle, or should there be no play at all. Or said a little better...how do you adjust the downshift rod at the carb end to get the proper results. Also, short of doing a road test, is there any way to determine you have it set up properly once everything is welded and adjusted?

Dewey

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Old 03-10-2005, 11:10 AM
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If this much of the theory is correct I think I can weld up the lever at the transmission correctly. (Actually, I've already tack welded it in a position which assumes the above is correct...so I might have to undo what I have if it's incorrect.) But then, how much play should I have at the carb when the engine is at idle, or should there be no play at all. Or said a little better...how do you adjust the downshift rod at the carb end to get the proper results. Also, short of doing a road test, is there any way to determine you have it set up properly once everything is welded and adjusted?
On the carb throttle lever should be attached a FORD kickdown attachment. The rod attaches to this. It allows the throttle shaft to move without necessarily activating the kickdown rod. Behind the actual throttle lever, you will see another lever with adjusting screw. You adjust this screw until you arrive at the kickdown RPM/road speed (road test) you desire. Extending the screw activates the rod sooner.
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Old 03-10-2005, 11:44 AM
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Be careful welding on that. You gonna melt the seal behind it
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Old 03-10-2005, 12:16 PM
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Thanks Kultulz. All the stuff you mention is there and seems to be operational. The carb lever connection, at present, seems to be somewhat sloppy. That is also true on my "good" C6 so I'm guessing that is how is supposed to be. There is probably about a half inch of play before the tab engages the down shift adjustment screw on the end of the down shift rod when you slowly open the throttle. So is it pretty much a matter of road testing then in order to get the response you want or is there a recommended adjustment to start with?

And Brainsboy,

Good heads up on welding around the shift lever. I was worried about that very thing so I removed what was left of the lever and did all the welding on my workbench. I probably would have gotten things a little more lined up to my liking if I'd tacked it while it was still on the car but I've had trouble with those little O ring seals leaking oil so I didn't want to take any chances.
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Old 03-10-2005, 12:24 PM
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Hey by the way, if you need some C-6 parts I have a core that I will probably never use. I can check on the kick down lever part if you want
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Old 03-10-2005, 01:51 PM
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So is it pretty much a matter of road testing then in order to get the response you want or is there a recommended adjustment to start with?
There most likely is an assembly adjustment, but I have no idea of what it is. I would just drive it and adjust it along the road until I got the kickdown to where I actually want it.
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Old 03-10-2005, 05:17 PM
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Originally Posted by brainsboy
Hey by the way, if you need some C-6 parts I have a core that I will probably never use. I can check on the kick down lever part if you want
That might be VERY helpful. Do you have the rod too or just the lever. Maybe you should PM me with the response...just so we don't clutter up the thread with a parts swap.
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