81 vette vent

I have an 81 with a 350 tranny. It shifts very smoothly through all gears. I had to add a kickdown linkage. It is connected down in the trans because it does pull my cable back. I do have it connected to the carb. I have it set so when I am at full throttle the linkage is pulled completely. BUT it doesn't ever shift down.

Am I missing something?

Brians1

I have an 81 as well and what I found out is that there is a Transmission Vacuum Line that runs down to the back right of the Tranny and connects to a Vacuum module. You may want to check your Vacuum hose and the module itself (its 10.99 at Auto Zone - just replaced mine). It works by using the vacuum (Ported i believe) and as vacuum increase/decreases it makes its decision around when to shift, the kick down cable is only used at WOT * I believe*

AutoZone calls it this: Transmission Modulator - Part # MV105

81 vette vent

Brian did your car shift smoothly before you changed your vacuum module? I thought the trans wouldn't even shift if the modulator wasn't working correctly.

Brians1

No it was rough, specifically reverse (some of it was timing) but the replacement of the module and some new vacuum hose for under 15 bucks.....I chose to do it. Shifts are smooth now. I know every car and suitation is different, but with the 81 CCC we prob share a lot of these same issues in common :P

Brians1

One Other thing to look at is the cable itself. It can be adjusted, simple tab..Pull up on it...Open the Carb to WOT and while open, set the tab back...this adjusts the Kick down cable. Only other thing I have done.

hugie82

The cable will ratchet forward when it's pulled to the max. Sometime the cable ratchets easier than it should and you might have to wire tie it in position.
One thing that always happened to me with th350 is whenever I installed a shift kit. I would lose the kick down function! If I pulled the cable by hand I could get it to kick down maybe once every 5 times of doing it. So I gave up and shifted manually.

81 vette vent

I think I have found the problem but I haven't tested it yet. It seems to have some spring tenison pulling back on it, so I was adjusting it to when the spring tension stops, but the cable is a little harder to pull when the kickdown valve actually is being activated / engaged. I readjusted the cable but I am in the middle of sanding her down for paint so the test will have to wait until she is done putting on her new color.
I will keep my fingers corssed and hope this is all it was.