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Topic: TCS System Info Help?

in Forum: C3 Driveline Components


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TCS System Info Help? (1/5)
 7/28/08 4:17pm
bio11
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Oklahoma City, OK - USA

Vette(s):
1972 LS5 Convertible,Auto.Targa Blue with Black Interior.


Joined: 4/1/2007
Posts: 432

Can anyone point me in the right direction to learn about the Transmission Control Spark System on my 72 LS5. I have conflicting information if it even had it on the LS5. I replaced all the wiring harnesses and it has a plug for a solinoid on the carb and for the distributor. When I got the car it had nothing on it. I do have it plugged into the transmission. Will this effect my tranny if the rest of the stuff is unplugged. Also no TCS temp sender in the passenger side head. This is driving me nuts.
Lonnie
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TCS System Info Help? (2/5)
 7/28/08 10:37pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
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Hmmm....I'm not sure, but I think they all had the TCS systems, but don't quote me on that.

The solenoid you speak of that goes on the carb has nothing to do with the TCS. It is for the "fast idle", or kick up, for when the A/C is on. It raises the idle RPM so the A/C doesn't drag the engine down at idle.

On the later cars, such as my '74(starting in '73, I think), it is used solely for an "Anti-Dieseling" solenoid. With the key off, it retracts, and closes the throttle blades completely, which keeps the engine from "dieseling" when shut off. If the idle speed stayed up, it would diesel. (Thanks to the Feds regulating the emissions...)

As far as the rest of the TCS system, for your year model, it would also include a 20-30 second "Delay" relay, which would delay the ign. vacuum advance for 20 or so seconds once shifted into 3rd or 4th. There would be a solenoid for that...perhaps this is the solenoid you're referring to.
I may have some info on your year car, in relation to the TCS and LS5, I'll have to go look it up. If I do, I'll post it for ya here in a little while, unless someone else can confirm or deny the application.


It is possible, btw, that the earlier automatic cars did not have the TCS...Adams' Apple2008-07-28 19:38:26

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Joel Adams
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TCS System Info Help? (3/5)
 7/28/08 11:33pm
bio11
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Oklahoma City, OK - USA

Vette(s):
1972 LS5 Convertible,Auto.Targa Blue with Black Interior.


Joined: 4/1/2007
Posts: 432

Thanks for any info you can provide Joel, you have already told me more than i've been able to find out so far. Should I leave the connection to the tranny plugged in? There is no solinoid for the distributor or a temp plug in the passenger side head.
TCS System Info Help? (4/5)
 7/29/08 12:07am
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 20126

What I have found is this...
From the MF Dobbins "68-72 Corvette Fact Book", the '72 LS5 that he shows a pic of does definitely have a TCS solenoid, bolted to one of the coil hold-down bolts. It has a metal line, that goes from the carb, back to the solenoid, and then a small vac. line from the solenoid to the dist. In the pics, the solenoid has been by-passed, but it is there.

Now then...is that one an automatic or 4 speed car? Can't really tell from the pics, but...I can't see the vac. line for the trans, so I assume, in this book anyway, that this one is a 4 speed. Emissions applications were different back then for autos compared to 4 speed/standards. For instance, in '74, auto equipped cars did NOT have smog pumps....only the 4 speed cars did...go figure.

Looking back to 71, there does appear to be a vac. line going to the carb idle-stop solenoid on the small block(base engine), but not on any of the other engines in '71. I seem to remember seeing them like this back in the day, but for the life of me, I can't remember why there would be vac. on the idle-stop solenoid...

I'm not sure where the temp sender for the TCS would be on a '72 big-block, but it could be in either head...just depends on where your connector for it is. I know on most small blocks, it is on the pass side.

You can leave the trans connector plugged in...it ain't gonna make any difference if you don't have the complete TCS system . If you unplug it, then you won't have a kick-down(passing gear), as that connector is also for the kick-down solenoid in the trans.


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Joel Adams
C3VR Lifetime Member #56    

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(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

TCS System Info Help? (5/5)
 7/29/08 8:07am
bio11
Former Member

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Oklahoma City, OK - USA

Vette(s):
1972 LS5 Convertible,Auto.Targa Blue with Black Interior.


Joined: 4/1/2007
Posts: 432

Thanks Joel, armed with the info you gave, I think I'll just leave it like it is. It seems to run well and the solinoids and stuff are very expensive.
Thanks again Joel, as always you have helped me a lot.
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