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4/2/14 9:40pm - Original Message: '1981 with RPM issue'
RedVetteinprogress
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West Bend, WI - USA

Vette(s):
1985 silver coupe & 1975 red coupe

Joined: 3/18/2010
Posts: 46
Hello out there from the still somewhat frozen state of Wisconsin. I bought a pretty nice 1981 car last summer to play with but it has a few problems. The computer is not in the system anymore and on the hwy the torque converter  isn't locking up because the RPM doesn't drop off. I have heard the thing can be wired with a switch inside for the hwy. How is that done? also, how much of an RPM difference should I see if it's working  right? Any help you guys can give me would be great!! Thanks, Darrell
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4/2/14 11:05pm - Reply: 'Re: 1981 with RPM issue'
Adams' Apple Lifetime 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: 19523
Lock up on a 350 trans will only drop the rpm about 200 rpm. A few things can keep the lock up from working, starting with a blown fuse(no power to the trans connector), a brake switch that is bad, or not adjusted properly, or a problem with the solenoids, or pressure switch inside the trans.
First thing to check is if there is 12v AT the trans connector with the key on. If there is voltage there, then the problem is the solenoid, or pressure switch. Thumbs Up

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Joel Adams
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4/3/14 9:27am - Reply: 'Re: 1981 with RPM issue'
Adams' Apple Lifetime 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: 19523
Now that I have re-read the post....the lock up will not work with the ECM out of the mix....
The ECM controls the ground side of the solenoid to energize it. You should have 12v at the connector even without the ECM in the loop, so what you need is a ground, which you can provide either with a toggle switch(on/off), or by re-wiring the harness inside the trans. The trans has a pressure switch inside that closes at a specific pressure, which happens to correspond to a specific MPH. You would need to change the pressure switch to one that closes around 45-50 psi/mph, and then cut one wire, and run it to ground inside the trans, and then your lock-up will engage as soon as the pressure switch closes.
Sounds a lot harder than it actually is to do. I think I have a wiring diagram specifically for this mod somewhere. I'll look for it....Geek



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Joel Adams
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4/3/14 8:26pm - Reply: 'Re: 1981 with RPM issue'
Sarge81 Lifetime Member
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WEST SENECA, NY - USA

Vette(s):
1981 Blue Ice Met. w/pearl ghost flames TKO500 5speed. LS1 Swap 3.45 Dana 44.

Joined: 12/3/2001
Posts: 2377
This topic brings back memories. 

I remember my father put a lighted toggle switch for the lock up converter on either his '81 or '85 Olds Gutlass Supreme. I believe he tapped into a wire off of or near the brake switch.  It's been so many years ago I can't remember exactly. He put it in there because the lock up feature use to kick in and out once the car was around 45 mph. It was annoying. so for around town it remained off. Once on the highway 55 mph and above he'd flip it on. 


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GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44
'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975




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