80 owners- please help.
Thread Starter
Race Director
Joined: Apr 2003
Posts: 13,300
Likes: 16
From: TX
St. Jude Donor '12-'13
80 owners- please help.
On my 80, the torque converter lockup does not work. On the freeway, I am at 3500 RPM at 65. The previous owner replaced the engine, and stripped out alot of stuff including the cruise control unit, and the lockup vacuum valve/switch.
If the car was originally equiped with cruise, does the cruise have to be installed for the lockup to work? or are they unrelated. Basically what Im asking is what are all the necessary components to have a functioning lockup converter?
Thanks for any help
Kevin
If the car was originally equiped with cruise, does the cruise have to be installed for the lockup to work? or are they unrelated. Basically what Im asking is what are all the necessary components to have a functioning lockup converter?
Thanks for any help
Kevin
Racer
Joined: May 2001
Posts: 472
Likes: 0
From: Tampa Bay Area
Re: 80 owners- please help. (clutchdust)
Yep in 1981, and i think that the cali cars in 80 had TC lockup.
To answer your question, yes and no, if the cruise control cancel switch under the brake pedal is removed then if the TC locks up the car would die on the freeway, b/c it could not disengage. So unless your car was bought in Cali, it should not have a TC lockup function.
[Modified by mean8t, 10:56 AM 5/8/2003]
To answer your question, yes and no, if the cruise control cancel switch under the brake pedal is removed then if the TC locks up the car would die on the freeway, b/c it could not disengage. So unless your car was bought in Cali, it should not have a TC lockup function.
[Modified by mean8t, 10:56 AM 5/8/2003]
Instructor
Joined: Mar 2003
Posts: 235
Likes: 0
Re: 80 owners- please help. (clutchdust)
I can not help you much on this sense I removed the vacuum switch on mine. But you do not need cruise for you to have a lock up converter. I don't know how it is hooked up as it as mostly gone when I got the car.
To clear it up just a bit... Yes there is such a thing as a lock up converter on a T-350. Both the standard t-350 and the lockup t-350 are around. I'm not sure what the difference is other than the converter. Most people I know put a stall converter in and eliminate the lock up anyways.
To clear it up just a bit... Yes there is such a thing as a lock up converter on a T-350. Both the standard t-350 and the lockup t-350 are around. I'm not sure what the difference is other than the converter. Most people I know put a stall converter in and eliminate the lock up anyways.
Thread Starter
Race Director
Joined: Apr 2003
Posts: 13,300
Likes: 16
From: TX
St. Jude Donor '12-'13
Re: 80 owners- please help. (IRON WILL)
you know, I just assumed that it once had the lockup function. I had done some research and thought that all 80s had it.
I guess this is good news- one less thing to worry about. With my high rpms, it seems my speed would top out at 85 or 90?? :confused:
(not that I plan to go that fast)
:)
[Modified by bhblue80, 8:57 PM 5/8/2003]
I guess this is good news- one less thing to worry about. With my high rpms, it seems my speed would top out at 85 or 90?? :confused:
(not that I plan to go that fast)
:)
[Modified by bhblue80, 8:57 PM 5/8/2003]
Drifting
Joined: Jul 1999
Posts: 1,542
Likes: 43
From: Plano TX
Re: 80 owners- please help. (bhblue80)
On my 80 L82 I removed the crusie becuase in is so unreliable. However this had no effect on the lockup system. To cause lockup, there is a vacuum switch mounted to the firewall just right of the dist if looking from the front of the car, the trans must be in 3rd gear, the brake switch must be closed and the govenor is used to sense when lockup should occur.
I had issues with the solenoid in the valve body becoming clogged every 20K miles causing the trans to lockup right at the 2nd to 3rd shift which is too low of an rpm. Was a real pain, so the last time this happened I just removed the solenoid from the valve body (lockup off is for fluid to pass through the solenoid into the pan and lockup closes the valve body port to the pan causing presure to build locking the converter.
It might be worth a few MPG, but with the lazy/stock 3:08 rear gear it's not that important.
dave
I had issues with the solenoid in the valve body becoming clogged every 20K miles causing the trans to lockup right at the 2nd to 3rd shift which is too low of an rpm. Was a real pain, so the last time this happened I just removed the solenoid from the valve body (lockup off is for fluid to pass through the solenoid into the pan and lockup closes the valve body port to the pan causing presure to build locking the converter.
It might be worth a few MPG, but with the lazy/stock 3:08 rear gear it's not that important.
dave
Melting Slicks
Joined: Aug 2001
Posts: 3,050
Likes: 124
From: Wichita KS
Re: 80 owners- please help. (bhblue80)
Figure 7A-2a Converter Clutch Controls on page 7A-3 (Section 7A) of the GM Corvette Shop Manual has a pretty good description of the lock-up control mechanism/operation.
The parts are available, I purchased my fender (firewall) mounted vacuum switch (original pn 14014519) from my Chevy dealer, as the original switch no longer closed properly. I purchased the switch to transmission wiring harness from Lectric Limited as my old harness was in pretty rough shape.
Page 403 of the 1980 A.I.M. has a drawing of the switch and vacuum delay valve (pn 14020690). The firewall mounted vacuum switch gets its signal from a Thermal Vacuum Switch (ported carb source) that opens if the coolant temperature is over 130 degrees F.
The parts are available, I purchased my fender (firewall) mounted vacuum switch (original pn 14014519) from my Chevy dealer, as the original switch no longer closed properly. I purchased the switch to transmission wiring harness from Lectric Limited as my old harness was in pretty rough shape.
Page 403 of the 1980 A.I.M. has a drawing of the switch and vacuum delay valve (pn 14020690). The firewall mounted vacuum switch gets its signal from a Thermal Vacuum Switch (ported carb source) that opens if the coolant temperature is over 130 degrees F.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Melting Slicks
Joined: Oct 1999
Posts: 2,581
Likes: 14
From: Tolar Texas
Re: 80 owners- please help. (bhblue80)
I believe that all 1980 Corvettes equipped with an automatic transmission came with the TH350C ("C" = w/lockup converter). Is the O.E. TH350C still in your car? It's possible that it was ditched in the past for a cheaper TH350 exhange.
I recently helped install a throttle body FI system (from Turbo City) on an '80 Chevy truck w/TH350C. The new computer was equipped to control the lockup converter. While installing the wiring harness, we found that the transmission had been replaced with a regular TH350. The current owner of this truck has owned it since new and he never realized that it had lost the lockup function after an earlier trans swap. Perhaps his old lockup converter had not worked in so long before the swap that he never missed it!?! Not a big deal.
The TH350C converter never locked up in my '80 prior to replacing it with a 700R4. But, I never tried to trouble shoot it either. Side note: I am using the O.E. vacuum switch to control current to the 700R4's converter.
I recently helped install a throttle body FI system (from Turbo City) on an '80 Chevy truck w/TH350C. The new computer was equipped to control the lockup converter. While installing the wiring harness, we found that the transmission had been replaced with a regular TH350. The current owner of this truck has owned it since new and he never realized that it had lost the lockup function after an earlier trans swap. Perhaps his old lockup converter had not worked in so long before the swap that he never missed it!?! Not a big deal.
The TH350C converter never locked up in my '80 prior to replacing it with a 700R4. But, I never tried to trouble shoot it either. Side note: I am using the O.E. vacuum switch to control current to the 700R4's converter.
Thread Starter
Race Director
Joined: Apr 2003
Posts: 13,300
Likes: 16
From: TX
St. Jude Donor '12-'13
Re: 80 owners- please help. (MIKER)
Thanks guys for the help.
Miker, its possible that the previous owner replaced the TH350C with a TH350- how would I tell the difference?
I am still thinking of installing the necessary components to get the lockup function (if I have the right trans.) The diagram shows the thermal control valve connected to a ported manifold source and the EGR. Since I have the ZZ4, there is no EGR. Would this outlet just be capped off?
Kevin
Miker, its possible that the previous owner replaced the TH350C with a TH350- how would I tell the difference?
I am still thinking of installing the necessary components to get the lockup function (if I have the right trans.) The diagram shows the thermal control valve connected to a ported manifold source and the EGR. Since I have the ZZ4, there is no EGR. Would this outlet just be capped off?
Kevin
Melting Slicks
Joined: Oct 1999
Posts: 2,581
Likes: 14
From: Tolar Texas
Re: 80 owners- please help. (bhblue80)
Miker, its possible that the previous owner replaced the TH350C with a TH350- how would I tell the difference?
The diagram shows the thermal control valve connected to a ported manifold source and the EGR. Since I have the ZZ4, there is no EGR. Would this outlet just be capped off?
Also, by design, the converter will unlock during hard acceleration due to reduced vacuum at the switch.
[EDITED to change description of electircal connector. I think it was a single wire connector.]
[Modified by MIKER, 10:31 AM 5/12/2003]
Racer
Joined: May 2000
Posts: 343
Likes: 0
From: Port Orchard Washington
Re: 80 owners- please help. (MIKER)
its a nice feature if it works - its kind of like 3rd and a half gear - good for the hiway - mine tends to shuttle on and off around 45 mph which bugs me - i plan to install a switch that cuts it out unless im at crusing speed - the vac switch kicks it out at hard accell - look for the electrical plug on the side - it should be easy to run a bubba style test switch just to check it- it will also help it run cooler - dave
