U just installed a 302/C4 combo in my buddies '66 Bronco. The C-4 was a Craigslist find and was supposedly good. Here's what it does. When shifting into D or R it acts normal. When accelerating gently it wind the motor to about 4k before shifting with a slam. 2 to D is not as bad but harsh. When it shifts while accelerating briskly it barks the tires. My questions are: Could this be cause by the lack of a kick down lever? Which port on the vacuum modulator gets vacuum and from where? Lastly, if this thing has some sort of shift kit in it, will replacing the VB solve the issue? The former motor was a I-6 and I've trying to figure it out as I go. Thanx in advance!

 

>bump< :

 

I am no expert but from your description, the trans sounds to be good.
The problems could certainly be caused by the kickdown not being connected, it may be in the kickdown position all the time. Could also be a no vacuum problem. The vacuum supply should be from the manifold (same as brake booster). As for the modulator my guess would be to use the outermost port (away from the trans case).

 

Thanx, I'll give that a try.