1986 automatic trans lockup question?
Thread Starter
Safety Car
Joined: Sep 2001
Posts: 4,162
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From: Glenbeulah Wi
1986 automatic trans lockup question?
I have a 1986 Vette with the auto trans and I believe the lockup feature of the transmission is not working correctly. As soon as the car shifts into second gear the transmission locks up the torque convertor, the engine bogs the rpm drop and the car shifts back into 1st gear. Once in first gear the car unlocks the torque convertor and then the car shifts back into second gear and operates correctly. The trans will stay unlocked until approximately 42 MPH and then it will relock the torque convertor and seem to operate correctly until I slow down. When I slow down the torque convertor will stay locked up until the car shifts back into first gear, the torque convertor electronic lockup circuit will stay grounded until the car comes to a complete stop, then it will disengage. Once I start moving the whole process will start over.
What is controlling the lockup feature, I know the computer controls the actual lockup but what sensors is the computer using to determine when the lockup should occur? I believe I have a failed sensor somewhere that is causing the lockup feature to operate incorrectly.
Any help would be appreciated.
What is controlling the lockup feature, I know the computer controls the actual lockup but what sensors is the computer using to determine when the lockup should occur? I believe I have a failed sensor somewhere that is causing the lockup feature to operate incorrectly.
Any help would be appreciated.
Instructor
Joined: Mar 2001
Posts: 230
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From: Phila. Pa.
Re: 1986 automatic trans lockup question? (bjankuski)
My 86 only locks up in 4th at 67 mph. I'm thinking it must have an aftermarket PROM. I dont think this is normal. My previous 84 acted like your 86 and it got on my nerves. I ended up pulling out the electrical plug on the left side of trans to keep the converter from locking up at all.
Advanced
Joined: Jul 2001
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Re: 1986 automatic trans lockup question? (bjankuski)
Your 86 is acting just like it should. The converter locks up in more than just OD. You can either change the chip, which is a little okay. Or, put a switch in line with the brake switch. I used a small rocker switch on the console right about where my right hand rested. With the switch you can leave it in OD and the car won't bog becaue it doesnt lock up until you flip the switch.
Team Owner
Joined: Sep 2001
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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Re: 1986 automatic trans lockup question? (RED90SIXLT1)
you can disable the torque converter by unplugging it? what all can happen if you do that? good or bad
Instructor
Joined: Mar 2001
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From: Phila. Pa.
Re: 1986 automatic trans lockup question? (vader86)
I ran my 84 a long time with the torque converter lock up disconnected (pulled electrical plug on left side of trans) and never experienced any problems. I don't think it will harm anything except a wee bit of fuel mileage.
Instructor
Joined: Mar 2001
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From: kissimmee,fl.
Re: 1986 automatic trans lockup question? (Cruz 86)
Iv been a transmission rebuilder for almost 20 years and can tell you that a 700r4 trans needs the lock up converter to work. If you disconect the converter clutch then when the trans is in 4th gear you loose about 90% of the lube oil going to the rear planeteary gears which is not a good thing!
Iv rebuilt a lot of 700r4 because of this.Do yourself a favor and dot do it.
Iv rebuilt a lot of 700r4 because of this.Do yourself a favor and dot do it.
Instructor
Joined: Mar 2001
Posts: 230
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From: Phila. Pa.
Re: 1986 automatic trans lockup question? (Rolla Dunkin)
Hey Rolla, Is it alright if the lock up only works in 4th or, does it starve for flluid in the other gears also? I guess I better find out why mine doesnt lock up until 67 mph and fix it.
