Another one with 4+3 tranny problems
Thread Starter
Instructor
Joined: Apr 2004
Posts: 217
Likes: 0
From: Winnipeg MB
Another one with 4+3 tranny problems
Hi
This is my first post as I just purchased a 86 Corvette with a 4+3 trans. I knew it was acting up, but have a few questions before I start troubleshooting. I drove it back about 300 miles and once you could get the overdrive to kick in it would stay in. It also kicks down fine on acceleration, but doesnt auto upshift like I think it is supposed after a downshift in 4th. When driving it, in any gear, after about 40-50+ pushes of the button it finally engages...and stays in OD. But as soon as I hit the button again once, it auto downshifts. Then I hit the button another 40 or so times....few miles later it engages....then I hit the button again once and downshifts fine. Could this be a relay that doesnt want to engage? Where can I check the wires from the button....do they go directly to the relay? If I have the key on or the car running in neutral....should the overdrive light come on without the car driving? This would be helpful in troubleshooting so I dont have to constantly road test. What else would cause a major delay in upshift, but nothing in downshift?
Thanx for the great forum!!
This is my first post as I just purchased a 86 Corvette with a 4+3 trans. I knew it was acting up, but have a few questions before I start troubleshooting. I drove it back about 300 miles and once you could get the overdrive to kick in it would stay in. It also kicks down fine on acceleration, but doesnt auto upshift like I think it is supposed after a downshift in 4th. When driving it, in any gear, after about 40-50+ pushes of the button it finally engages...and stays in OD. But as soon as I hit the button again once, it auto downshifts. Then I hit the button another 40 or so times....few miles later it engages....then I hit the button again once and downshifts fine. Could this be a relay that doesnt want to engage? Where can I check the wires from the button....do they go directly to the relay? If I have the key on or the car running in neutral....should the overdrive light come on without the car driving? This would be helpful in troubleshooting so I dont have to constantly road test. What else would cause a major delay in upshift, but nothing in downshift?
Thanx for the great forum!!
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: Another one with 4+3 tranny problems (Jinxie)
First question... does the overdrive light come on only and everytime the car is actually in Overdrive?
Could just be a bad shifter switch.
BTW, the relay is located between the brake booster and wiper motor. I think its the one in front. There's also a fuel pump relay there that is the same part number...
Try switching those two harnesses and seeing if it works then.... and if the fuel pump quits priming properly instead. :lol: That would indicate a bad relay.
BTW, the overdrive light will only come on when the overdrive solenoid is actually engaged... which only occurs under certain parameters. With the car in neutral, it won't, since the internal ATF pressure switch will open, cutting the 12V from the solenoid. For a simulated test, just put the rear end up on jackstands. We had my roommates Cobra on stands, and were doing 120mph in the garage with no problems. Just make sure everything is stable, shift smoothly, and don't punch the throttle too quick.
[Modified by CentralCoaster, 2:39 PM 4/16/2004]
Could just be a bad shifter switch.
BTW, the relay is located between the brake booster and wiper motor. I think its the one in front. There's also a fuel pump relay there that is the same part number...
Try switching those two harnesses and seeing if it works then.... and if the fuel pump quits priming properly instead. :lol: That would indicate a bad relay.
BTW, the overdrive light will only come on when the overdrive solenoid is actually engaged... which only occurs under certain parameters. With the car in neutral, it won't, since the internal ATF pressure switch will open, cutting the 12V from the solenoid. For a simulated test, just put the rear end up on jackstands. We had my roommates Cobra on stands, and were doing 120mph in the garage with no problems. Just make sure everything is stable, shift smoothly, and don't punch the throttle too quick.
[Modified by CentralCoaster, 2:39 PM 4/16/2004]
Instructor
Joined: Apr 2004
Posts: 120
Likes: 0
From: Close to Pittsburgh PA
Re: Another one with 4+3 tranny problems (Jinxie)
its probably a problem with the switch itself...I had tons of problems with my 88... i eventualy replaced the switch and adjusted it up and all is well...
Tom
[Modified by 88Blackonblack, 5:35 PM 4/16/2004]
Tom
[Modified by 88Blackonblack, 5:35 PM 4/16/2004]
Safety Car
Joined: Mar 2000
Posts: 3,581
Likes: 1
From: Springfield VA
Re: Another one with 4+3 tranny problems (Jinxie)
:iagree:
Just to be on the safe side be sure to check the fluid level. When you open the fill plug you should be able to touch the fluid. If it isn't there add enough to bring it up.
You can use Mobil 1 ATF synthetic to top it off if you need to. It seems to help them in shifting and quiets them down a little.
Just to be on the safe side be sure to check the fluid level. When you open the fill plug you should be able to touch the fluid. If it isn't there add enough to bring it up.
You can use Mobil 1 ATF synthetic to top it off if you need to. It seems to help them in shifting and quiets them down a little.
Thread Starter
Instructor
Joined: Apr 2004
Posts: 217
Likes: 0
From: Winnipeg MB
Re: Another one with 4+3 tranny problems (CentralCoaster)
The light comes on only when in overdrive and everytime in overdrive.
How does the shifter switch come out of the shifter....does the top just "pop" off?
I will check the relay first and go from there.
thanx
How does the shifter switch come out of the shifter....does the top just "pop" off?
I will check the relay first and go from there.
thanx
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Re: Another one with 4+3 tranny problems (Jinxie)
Carefully price the O/d button in the **** off and under neath is a "T" and a steel wedge. Undo the "T" counting the no of turns then pull the wedge out.This allows the **** to be undone .After removing the boot the button is on the front of the shift lever.Most people replace it with one from Radio Shack or similar.Need right type for your model ;some are off/on, others are momentary on.
Have shifter out of car at present , email me if you want some pics.
Have shifter out of car at present , email me if you want some pics.
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