4+3 wont go into OD in any gear
#1
Safety Car
Thread Starter
4+3 wont go into OD in any gear
I discovered a problem today
I drove into work and car was fine
But now when i left work
My 4+3 will not go into OD in any gear(2-4)
When i press the button on shifter OD light come on ok ,But will not go into Over drive.
Can someone tell me what may be causing this.Is the OD unit gone??
Maybe a bad selnoid??
FSM says there is a fuse but where??
Is there a Relay on the 4+3 anyone know of??
Please help
Thank you
I drove into work and car was fine
But now when i left work
My 4+3 will not go into OD in any gear(2-4)
When i press the button on shifter OD light come on ok ,But will not go into Over drive.
Can someone tell me what may be causing this.Is the OD unit gone??
Maybe a bad selnoid??
FSM says there is a fuse but where??
Is there a Relay on the 4+3 anyone know of??
Please help
Thank you
#2
The overdrive on our '85 happens to not work either, but its probably due to a bitten-through wire (we had mice living in the car).
I extrapolate from your avatar that youve got either an '84 or '85, so here goes: The OD relay is to the left of the brake booster, viewed from the front of the car. It takes maybe 10 seconds to remove the two nuts that hold it on. And, just in case you might want to know, the relay on a slightly higher level behind it the fuel pump relay. Good luck on solving the issue.
I extrapolate from your avatar that youve got either an '84 or '85, so here goes: The OD relay is to the left of the brake booster, viewed from the front of the car. It takes maybe 10 seconds to remove the two nuts that hold it on. And, just in case you might want to know, the relay on a slightly higher level behind it the fuel pump relay. Good luck on solving the issue.
#3
Melting Slicks
Did you stall it out when leaving work? Mine won't engage after stalling, unless you let the car sit for a couple of minutes. Also, check the fluid level in the OD unit.
#4
Team Owner
There's also a cable that runs from the throttle bracket down to the OD unit. With OD light on, might be the relay or the cable.
#5
Team Owner
What was the coolant temperature saying on the dash? Yes, there is a relay for the overdrive mounted on the firwall kind of between the distributor and brake vacuum booster. The fuel pump relay and it are identical, so you got a 50/50 shot of pulling the right one.
#6
Safety Car
Thread Starter
Thank very much guys and gals
My vette is a 1986 1/2
I did see 2 relays next to the distributor of the same part#.
Would one of those be the relay??
I drove the car on the highway home about est 75 miles in 4th gear and it tach around 2700 at 65mph and temp was great never once overheated or ran hot,Stayed around 168-172 degrees(i also have a chip in my ecm plus a 180 stat) so that pretty normal temps for my vette before this issue(just sucked up more gas)which is normal without OD on.
Does anyone think this problem is a BIG one? or something small?
I didnt smell any burning smells of tranny fuild nothing.
What i mean is should i pull the 4+3 is it gone???or something electrical??(like a relay )
Another thing im wondering is if it was a relay would the SES light come on and the OD light still work??
Thats what getting to me is the OD light still comes on when I press the button but doesnt go into OD.
Thank you all again for your replies it meens alot to me
I need a lift right now because im very depressed about my vette being almost the end of summer and not enjoying it as we speak
My vette is a 1986 1/2
I did see 2 relays next to the distributor of the same part#.
Would one of those be the relay??
I drove the car on the highway home about est 75 miles in 4th gear and it tach around 2700 at 65mph and temp was great never once overheated or ran hot,Stayed around 168-172 degrees(i also have a chip in my ecm plus a 180 stat) so that pretty normal temps for my vette before this issue(just sucked up more gas)which is normal without OD on.
Does anyone think this problem is a BIG one? or something small?
I didnt smell any burning smells of tranny fuild nothing.
What i mean is should i pull the 4+3 is it gone???or something electrical??(like a relay )
Another thing im wondering is if it was a relay would the SES light come on and the OD light still work??
Thats what getting to me is the OD light still comes on when I press the button but doesnt go into OD.
Thank you all again for your replies it meens alot to me
I need a lift right now because im very depressed about my vette being almost the end of summer and not enjoying it as we speak
#7
Team Owner
Originally Posted by Repzard
My vette is a 1986 1/2
I did see 2 relays next to the distributor of the same part#.
Would one of those be the relay??
Would one of those be the relay??
I drove the car on the highway home about est 75 miles in 4th gear and it tach around 2700 at 65mph and temp was great never once overheated or ran hot,Stayed around 168-172 degrees(i also have a chip in my ecm plus a 180 stat) so that pretty normal temps for my vette before this issue(just sucked up more gas)which is normal without OD on.
Does anyone think this problem is a BIG one? or something small?
I didnt smell any burning smells of tranny fuild nothing.
I didnt smell any burning smells of tranny fuild nothing.
What i mean is should i pull the 4+3 is it gone???or something electrical??(like a relay )
Another thing im wondering is if it was a relay would the SES light come on and the OD light still work??
Thats what getting to me is the OD light still comes on when I press the button but doesnt go into OD.
#8
Drifting
I have a Vette book that says the most likely cause for a failed OD unit is a bad second gear switch. The second gear switch tells the unit that it can kick into overdrive. The book is called 101 Projects for Your Corvette by MotorBooks. It also says that you can bypass this switch and make the OD kick on only when you hit the button, which is also a cure for a bad second gear switch.
#9
Team Owner
Member Since: May 2002
Location: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Posts: 24,337
Likes: 0
Received 17 Likes
on
16 Posts
Gear switches, coolant temp, shift **** switch are all inputs to the overdrive relay.
The overdrive 12V signal and dash light are outputs from the relay... (ie, they won't come on unless all the inputs work, and the relay works.) If the dash indicator comes on, then the 12V signal is being sent to the overdrive unit.
Most likely, your connector came loose from the side of the transmission, or the fluid level is low inside the overdrive causing the internal pressure switch to open. Both are easy fixes. Is the back of the transmission covered in grime? Low fluid level typically starts causing the overdrive to cut out intermittently, and gets worse as the level gets lower until finally never coming on.
Other possible causes are mechanical failure in the overdrive, or a broken signal wire, or a bad internal solenoid.
While you're nosing around in there, check the wire harness to your overdrive relay and fuel pump relay. The heat tends to shrink the insulation way back and cause shorts.
The overdrive 12V signal and dash light are outputs from the relay... (ie, they won't come on unless all the inputs work, and the relay works.) If the dash indicator comes on, then the 12V signal is being sent to the overdrive unit.
Most likely, your connector came loose from the side of the transmission, or the fluid level is low inside the overdrive causing the internal pressure switch to open. Both are easy fixes. Is the back of the transmission covered in grime? Low fluid level typically starts causing the overdrive to cut out intermittently, and gets worse as the level gets lower until finally never coming on.
Other possible causes are mechanical failure in the overdrive, or a broken signal wire, or a bad internal solenoid.
While you're nosing around in there, check the wire harness to your overdrive relay and fuel pump relay. The heat tends to shrink the insulation way back and cause shorts.
Last edited by CentralCoaster; 08-25-2006 at 12:32 AM.
#10
Burning Brakes
Member Since: Aug 2005
Location: Lewisvlle NC
Posts: 862
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Siveck
I have a Vette book that says the most likely cause for a failed OD unit is a bad second gear switch. The second gear switch tells the unit that it can kick into overdrive. The book is called 101 Projects for Your Corvette by MotorBooks. It also says that you can bypass this switch and make the OD kick on only when you hit the button, which is also a cure for a bad second gear switch.
#11
Team Owner
Originally Posted by CentralCoaster
The overdrive 12V signal and dash light are outputs from the relay... (ie, they won't come on unless all the inputs work, and the relay works.) If the dash indicator comes on, then the 12V signal is being sent to the overdrive unit.
#12
Team Owner
Member Since: May 2002
Location: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Posts: 24,337
Likes: 0
Received 17 Likes
on
16 Posts
Originally Posted by scorp508
I can't remember right now, but does the dash light come on if the relay gets the 12V, or only when the relay activates? What if it is a stuck relay?
And if you put it in diagnostic mode, it ignores all the inputs and sends 12V but doesn't activate the solenoid if the pressure is too low. But it will activate the relay and light.
#13
Originally Posted by Grenkepr
That is what I did. Fixed the same problem. Like this setup better anyway. Now I can shift when I want to.
#14
Team Owner
Originally Posted by CentralCoaster
And if you put it in diagnostic mode, it ignores all the inputs and sends 12V but doesn't activate the solenoid if the pressure is too low. But it will activate the relay and light.