4th gear lock up 85 C4
Thread Starter
Intermediate
Joined: Jun 2020
Posts: 42
Likes: 0
From: Russellville, Ar.
4th gear lock up 85 C4
Trying to find the easiest way to lock up 4th in my 700r4. I haven't dropped pan yet and not sure if I have 1 pin solenoid or 2 pin? http://www.chevyasylum.com/tech/4thgear.html just would like to double check this diagram. I hate to drop pan at shop and have 2 pin and not be able to fix and have to order part and do it all over again!
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Lockup
Do u mean converter lockup?
when you are driving, can u count 3 shifts?
your converter lockup is disengaged by the brake pedal after it locks up.
so get the car at 50mph, push gently on the brake before it starts to slow u down. It should feel like it downshifts.
if it does, its working.
you might just have to change Or adjust your brake light switch instead Of dig into trans.
try ohming the converter solenoid to see if the coil is open.
a lot of the time, it’s what moves (brake pedal) that caused a failure.
if u see how cheaply made those switches are, you would go there first.
anyhoo, the harness is easy to see.
jack up your car like you would change oil, and look at your connector, how many wires are in it?
white 4 pin plug
when you are driving, can u count 3 shifts?
your converter lockup is disengaged by the brake pedal after it locks up.
so get the car at 50mph, push gently on the brake before it starts to slow u down. It should feel like it downshifts.
if it does, its working.
you might just have to change Or adjust your brake light switch instead Of dig into trans.
try ohming the converter solenoid to see if the coil is open.
a lot of the time, it’s what moves (brake pedal) that caused a failure.
if u see how cheaply made those switches are, you would go there first.
anyhoo, the harness is easy to see.
jack up your car like you would change oil, and look at your connector, how many wires are in it?
white 4 pin plug
Last edited by coupeguy2001; Aug 18, 2020 at 03:27 PM.
Thread Starter
Intermediate
Joined: Jun 2020
Posts: 42
Likes: 0
From: Russellville, Ar.
YES , I do mean converter lockup...sorry 
. Yes it does shift 3 times. I will have to check and see if it downshifts. I have converted my vette to aspirated and do not rely on computer. I was told that when I converted over that I would have to lockup torque converter.
. Yes it does shift 3 times. I will have to check and see if it downshifts. I have converted my vette to aspirated and do not rely on computer. I was told that when I converted over that I would have to lockup torque converter.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Lockup
Even if your computer does not configure fuel mixture, it can still run the converter lockup.
your vss is active: You can still have the oxygen sensor hooked up, it can still run your ignition, you just have to take the bulb out if your check engine light.
it can even use the knock sensor.
replace the fuel pump with a low pressure pump, and go for it.
just pull the 2 injector fuses and hide the injector connectors.
the computer runs the cooling fan too.
your vss is active: You can still have the oxygen sensor hooked up, it can still run your ignition, you just have to take the bulb out if your check engine light.
it can even use the knock sensor.
replace the fuel pump with a low pressure pump, and go for it.
just pull the 2 injector fuses and hide the injector connectors.
the computer runs the cooling fan too.
Drifting
Joined: Jun 2018
Posts: 1,678
Likes: 229
From: Michigan
Just slowly accelerate, once in OD around 45mph you should feel like it dumped into 5th too early and slight accelerator pressure results feel like a car in 5th too early, 25% TPS should unlock, RPMs come up and the car feels free again.
The lock up is to help with gas mileage and heat.
This function is available in 3rd and 4th gear operation. Most want to do a switch to be able to lock it in manually to improve ETs. The diagram your lined to states "4th gear function only" . Is that what you want or do you want to be able to lock the Torque Converter Manually. Do you want that to only be manually or do you want the ecm to be able to control it and you be able to override it too?
Just making sure you are asking the right questions because I have seen a few threads where the results of TCC function were what the person asked after they performed the modification, but wasn't what they meant.
Burning Brakes
Joined: Nov 2015
Posts: 762
Likes: 94
From: Airdrie Alberta
I use a manual lock-up switch for my 85 vette. No need to drop pan, the lock-up connector is on the driver side of the transmission. If you want to get fancy yo can install a hobbs pressure switch on the 4th gear pressure port (passenger side) so you can get lock-up only in fourth gear.
TCI also sells a kit.
I made my own kit, was alot less money.
TCI also sells a kit.
I made my own kit, was alot less money.
Last edited by Mike Holmen; Aug 20, 2020 at 10:47 AM.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Kyle
I have been ahead on a few contests of speed, and when it looks like I’m gonna get whupped, i just touch the brake pedal, unlock the converter.
a lot of the time the other guy thinks i am hitting the brakes, starts to slow, and it's like Having another gear. I just take off.
still funny. 😳
what good is having a corvette if u can’t have fun with it
a lot of the time the other guy thinks i am hitting the brakes, starts to slow, and it's like Having another gear. I just take off.
still funny. 😳
what good is having a corvette if u can’t have fun with it
Last edited by coupeguy2001; Aug 21, 2020 at 03:22 PM.
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