I had my transmission rebuilt in my '66 coupe. During mild acceleration it shifts from 1-2 and 2-3 normally. While cruising about 40 MPH I let off the gas and it kicks down into second gear. It's driving me crazy. Everything looks normal. The car has a '72 302 in it that originally had the stock carb and intake on it. I installed an Edelbrock Performer intake and a Holley 4Barrel carb. I had the same problem BEFORE I had the transmission rebuilt so now I'm kind of at a loss as to where to look for the problem. My vacum line looks new and everything seems connected. ANY assistance??????????????????

 

I assume you have a C4 in it.. Try looking at the linkage and see if it's setup right and adjusted. It sounds like the kick down linkage (or cable if you changed it) is not setup right.

 

It's either the kick down linkage or the modulator. Both are adjustable.

 

What I did with the kickdown linkage was fabricate a slider so that the kickdown actuator on the transmission is pulled under hard acceleration. I don't have a problem with the car kicking down when I punch it so I think it's set up right. I'm pretty sure it has to be the modulator now but my question is how exactly do I go about adjusting it? I assume I'd take the vacum tube off but I'm not sure what to do after that. Is it an adjustment screw? Which way do I turn it? Is it one of those "adjust it, test drive and adjust it again until it's right" kind of things?

 

That is about right. I can never remember wich way is which on the adjustment but it is usually a small screwdriver or allen wrench. Try one way, if that doesn't work go the other.

 

Sounds to me like a misadjusted throttle valve linkage. What people normaly refer to as a kick down lever. It does alot more than just a kick down and must be adjusted correctly or the trans wont work correctly.. Here are some instructions I photgraphed from my trans manual. I figured pics would be better than me retyping all of it, since I hate typing something I am reading, and so you would know I am not just pullin it out of thin air or something..

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