how to use '68 TH400 kickdown switch with Chevrolet Truck Rochester Quadrajet? - Firebird Classifieds & Forums (1967, 1968, and 1969)

Hi there,

I have (what I believe is) an original TH400 kickdown switch on my Pontiac 400 with TH400 transmission.

I currently have a R4-M4MC Quadrajet mounted up.

While the kickdown switch bracket which I bought seems to work, the carb lever arm will not make contact with the kickdown switch at full throttle.

(see attached picture 1&2)

I am wondering, can I buy something like this:

(see attached picture #3)

In order to get my non-Pontiac Quadrajet working with the kickdown switch?

Attached picture carb-throttle-arm2.jpg

I see you have an aluminum intake so I think you might be OK with an aftermarket solution. If so you might be OK with my setup. I'm using a Lokar kit like the one I had on a street rod. You might want to check this out. I have mine so you don't really notice the main mechanism because I bolted it to the trans. pan.
Doug

The short answer is NO, that throttle arm will not work with your current set up.
You need a Pontiac primary shaft that will accept the bolt on throttle arm, I believe 67-71 were the only years for that primary shaft, you can get them aftermarket, but they are junk...ask me how I know.
I obtained a good original one without snapped off throttle blade screws.
Here is what you are looking for.

Attached picture carb1.JPG

Originally Posted by Dr. Drivability

You need a Pontiac primary shaft that will accept the bolt on throttle arm, I believe 67-71 were the only years for that primary shaft, you can get them aftermarket, but they are junk...ask me how I know.

Ok, how do you know? I bought one of those aftermarket shafts, but haven't installed it yet. What sort of trouble is it going to give me?

- Pete

Originally Posted by Pete67400

Originally Posted by Dr. Drivability

You need a Pontiac primary shaft that will accept the bolt on throttle arm, I believe 67-71 were the only years for that primary shaft, you can get them aftermarket, but they are junk...ask me how I know.

Ok, how do you know? I bought one of those aftermarket shafts, but haven't installed it yet. What sort of trouble is it going to give me?

- Pete

I bought one and installed it, it was fine when the car was cold, but the crap metal (likely chinese) expanded in the baseplate bores and did not allow the throttle to return to idle when the engine was fully warmed up....dangerous.

And I tried it in 2 different baseplates...very labor intensive to swap.
Go to Cliff Ruggles site and look up a guy "Mr. Pontiac" he has all kinds of stuff, that's where I got mine from...expect to pay a premium ~50 bucks.

Originally Posted by Dr. Drivability

Originally Posted by Pete67400

Originally Posted by Dr. Drivability

You need a Pontiac primary shaft that will accept the bolt on throttle arm, I believe 67-71 were the only years for that primary shaft, you can get them aftermarket, but they are junk...ask me how I know.

Ok, how do you know? I bought one of those aftermarket shafts, but haven't installed it yet. What sort of trouble is it going to give me?

- Pete

I bought one and installed it, it was fine when the car was cold, but the crap metal (likely chinese) expanded in the baseplate bores and did not allow the throttle to return to idle when the engine was fully warmed up....dangerous.

And I tried it in 2 different baseplates...very labor intensive to swap.
Go to Cliff Ruggles site and look up a guy "Mr. Pontiac" he has all kinds of stuff, that's where I got mine from...expect to pay a premium ~50 bucks.

Thanks Doc! It would have certainly been frustrating to learn this the hard way. Doesn't look like any of the aftermarket shafts are advertised as working for my carburetor anyway (they're made for Buick/Oldsmobile Quadrajets, whereas mine is a Chevy), so I guess I'll get an aftermarket kickdown switch & eventually sell this original one.

Sent a PM