What ive got. 1986 5.0 rebuilt 1980s small block c6 case 1967 C6 internals and appropriate stock torque converter 1967 C6 to 67' 390 stock kickdown what came with the truck. fits perfectly TCI Manumatic Shift kit and valve body the 67 didnt work in the modern case... and vice versa...forget all the reasons but it wouldnt go to third. For the last 8 months Since Ive had my engine and tranny rebuilt... Ive been wrestling with the kickdown adjustment to my edelbrock carb ( ive got the ford adapter kit)... The issues I was haveing are irratic shifting when under moderate to heavy pedal... I would almost no matter what get a hard down shift and up shift and a down shift and back up... Next I was having what I thought was driveline vibrations... after much agrivation I decided to pull the kick down off... The majority if not almost all of the vibration went away... it shifts fine.. and runs through the power band or whatever much better... It doesnt down shift on demand (pass gear) but with the manumatic I can do that. It acutally feels stronger when accelerating. left me scratching my head... another weird thing... my rpms dropped... used to if I was running 55 I was turning an easy 3500 rpm. and now its 600 or so less... I was shocked. dont really get that. my question is ... What the heck was going on.. why was it causing vibration and why would it drop the rpms? im no transmission guy.. please advise. if Im not going to tear it up... ( I know some people dont use them ) Im thinking just leave the kick down off. shish.
A couple of guesses, bearing in mind that I'm not a C6 guru. The '66 & '67 C6s have a different valve body than later C6s, which may account for your case woes. So far as the C6 kickdown...you can leave it off with no problems, as you've found. What people tend to overlook with trans kickdowns (& TV cables for the overdrive automatics, for that matter) is that it's not just about the amount of travel...there is often issues of geometry involved. I've seen a number of cases where the overall amount of travel may be correct, but the rate of linkage movement is not (I'm speaking in generalities here, not necessarily about your trans). It's similar to the question of carburetor linkage: progressive vs. direct. Sometimes brackets, even aftermarket ones, cause problems. You may be getting excessive kickdown movement at part throttle, even though the movement at full throttle looks OK when you look at things. It sounds as if the kickdown is causing the valve body to direct fluid incorrectly...not enough line pressure, etc. Something, anyway. Perhaps you are/were getting clutch slippage at cruise (55 mph), which isn't good & leads to quick wear. I'd look at the fluid & consider pulling the pan & looking to see how much clutch dust is in it, if you've been driving it this way for any real length of time. At any rate, leave it off & have fun manually shifting! Hopefully a transmission guy will add to this.
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