What's this?
 

I know this is on a Pontiac (please don't rip me) but my 70 chev. p/up also had one. A guy on the Pontiac Forum wants to know and no one has figured it out. I thought it went to the air cleaner, regulating the fresh air flow from outside to hot air by exhaust, but i was never 100% sure . Thanks!

Re: What's this?
 

Appears to be a TH400 kickdown switch

Re: What's this?
 

It may be part of the anti-dieseling solenoid. I believe that 72 trucks had a vacuum pod like this that was connected to the carb and distributor. Power ran from the trans. to the vacuum pod then to the carb solenoid. 72 solenoid had one electrical connection.

71 had a similar setup, but it combined the vacuum on the back of the solenoid. 71 solenoid has two vacuum ports, and two electrical connections.

Re: What's this?
 

IIRC it's a tvs. Transmission vacuum solenoid. Had one on my chevelle. One wire is powered. The other goes down to a switch on the transmission on a 4 speed tranny.
When you finally shift to 4th the switch on the tranny provides a ground. The vacuum switch opens and allows vacuum to the vacuum advance on your distributor. Lots of high compression motors ran like that. Very aggressive timing curve in the distributor but vacuum advance only under cruise conditions.

Re: What's this?
 

Geezer is right, only I think it is called TCS solenoid (trans controlled spark)

Re: What's this?
 

TCS solenoid is what I was talking about too.

Re: What's this?
 

My 70 had the TCS system on it, but I don't recall a vacuum line, only a wire that ran from the solenoid to a relay box one the firewall and then down to a switch on the side cover of the trans.

Re: What's this?
 

That was probably the kickdown for your tranny if you had a T400 in it. Different beast!!! LOL!!!

Re: What's this?
 

I have a t4000 trans, I don't remember any extra wires or switches on my trans though.
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Re: What's this?
 

Nope, it was a 3 on the tree. It was definitely TCS, because I thought the switch on the trans was for the backup lights, and when I traced the wire and found what it was connected to, I looked it up and found out what it really was for.

Re: What's this?
 

That is part of the TCS system. It was plumbed in line with the vac line feeding the distributor. It would shut off the vacume unless the tranny was in top gear and regular engine temp was reached.

Re: What's this?
 

Forget it, geezer # 99 and John are right. yOU CAN FIND MORE INFO HERE