So I recently rebuilt the automatic C6 transmission on my 1977 F150. I thought when I put the valve body back on that I had everything lined up properly (specifically the kickdown mechanism). But for some reason it doesn't seem to work properly because when I press the gas hard (to get up a hill or pass someone) it won't shift up. It's a little hard to explain what I'm looking at, but basically before I pulled the truck apart I notice that when the throttle was in the Idle position the kickdown lever on the transmission was almost parallel with the main drive shaft facing forward, but now it is in that position but is unable to go down when I push the gas. I was able to bend the kick down rod so that when the throttle is at idle now the lever on the transmission is up at about a 45 degree angle from parallel with the shaft, and when I push the gas it goes down to parallel. I'm sorry if none of this makes sense I'm having trouble explaining it. Anyway if anyone knows anything about how the kickdown is supposed to look at idle or what its exact angle and movement of travel is I would appreciate knowing that. Also I don't think the problem is the vacuum modulator because I tried softening up the shift on that and it didn't change anything.... Also I never drove the truck before I fixed the transmission (it didn't move and my buddy said I could have the truck if I fix it, so I did) so ya I'm kind of just guessing on what the drive is supposed to feel like. Thanks

 

Welcome to the forum Bryce. If you have photos, post them up for us to see what you're speaking about.

Technical stuff like this is quite hard to describe on a forum and pictures are worth 1000 words.

While you're posting up pictures, tell us more about your intake, carb, carb riser (if it has one), and engine combination so we can get a sense of what you're working with.

I'm sure we'll be able to help you out, just need a little bit more info.

 

Something like this?

 

the kickdown is adjustable, it should be adjusted so that at wide open throttle the linkage just bottoms out the transmission actuator. Now, a common issue is the little finger inside the transmission case gets clocked wrong, or mis aligned preventing the linkage from actuation the valve body. check the kickdown lever to be sure it is actually actuating the valve inside the trans.

 

Does the lever on the transmission spring back when pulled down? Sounds like the lockdown may not be in the detent of the valve body.

 

thats what I think too, you said it better.

 

Ya that's what I am thinking the problem is, should it spring back automatically at the transmission or do you just mean that it springs back from the throttle mechanism pulling on it. The picture is where it is located at its upper travel limit. I think that it is supposed to be lower and be pushed farther down when the throttle is pushed. I was somewhat suspicious that I might have not located the arm correctly before attaching the valve body. Thanks for the info, I think I am going to take the pan off just to double check.