What's this? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

custom1970 · 05-12-2011, 01:51 PM

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!

c1069 · 05-12-2011, 01:57 PM

Appears to be a TH400 kickdown switch

boundstaffpress · 05-12-2011, 02:41 PM

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.

geezer#99 · 05-12-2011, 03:19 PM

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.

**john** · 05-12-2011, 03:40 PM

Quote:

Originally Posted by geezer#99

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.

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

boundstaffpress · 05-12-2011, 05:19 PM

TCS solenoid is what I was talking about too.

**70STOVEBOLT** · 05-12-2011, 05:27 PM

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.

geezer#99 · 05-12-2011, 05:43 PM

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

custom1970 · 05-12-2011, 08:11 PM

Quote:

Originally Posted by geezer#99

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.

I have a t4000 trans, I don't remember any extra wires or switches on my trans though.
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**70STOVEBOLT** · 05-13-2011, 07:54 AM

Quote:

Originally Posted by geezer#99

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

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.

Longhorn Man · 05-13-2011, 05:52 PM

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.

c1069 · 05-13-2011, 08:48 PM

Quote:

Originally Posted by c1069

Appears to be a TH400 kickdown switch

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

05-12-2011, 01:51 PM	#1
custom1970 Member Join Date: Jan 2011 Location: Stuart, Florida Posts: 467	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! Attached Images

05-12-2011, 01:57 PM	#2
c1069 Registered User Join Date: Apr 2010 Location: McFarland CA Posts: 1,392	Re: What's this? Appears to be a TH400 kickdown switch __________________ Pancho 69 c/10 step side 454/400 with 3.07

05-12-2011, 02:41 PM	#3
boundstaffpress Jamie Hyneman is my twin Join Date: Nov 2005 Location: La Junta, Colorado Posts: 705	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. __________________ Justin SOLD 1967 K10 Fleetside, 283, Front and Rear Posi SOLD Color Wiring Diagrams Now in High Resolution V8 and Cab and Cab and Chassis

05-12-2011, 03:19 PM	#4
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,712	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.

05-12-2011, 05:19 PM	#6
boundstaffpress Jamie Hyneman is my twin Join Date: Nov 2005 Location: La Junta, Colorado Posts: 705	Re: What's this? TCS solenoid is what I was talking about too. __________________ Justin SOLD 1967 K10 Fleetside, 283, Front and Rear Posi SOLD Color Wiring Diagrams Now in High Resolution V8 and Cab and Cab and Chassis

05-12-2011, 05:27 PM	#7
70STOVEBOLT Senior Member Join Date: Jun 2005 Location: Winona Lake, IN Posts: 6,357	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. __________________ 70 C/10 SWB 402/TH400/3.73 "The Needy Beast" 200,000 Mile Club Disc Brake Club Owner installed options: Front Sway Bar Power Steering Power Brakes Cigar Lighter Courtesy Lights Deluxe Side Markers Wiper Delay Sliding Rear Window Power Windows Power Locks Sniper EFI 2015 Silverado 1500 LS 4.3/6L80/3.23 lowered 2" front & rear

05-12-2011, 05:43 PM	#8
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,712	Re: What's this? That was probably the kickdown for your tranny if you had a T400 in it. Different beast!!! LOL!!!

05-13-2011, 05:52 PM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	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.

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