In cruise,o'drive will not engage. When I back off accelerator,o'drve engages. If i back off a couple hundred rpm,o'drive will engage until rpm stabilizes then kicks off again. Is this a computer problem or a problem with the o'drive unit itself.

 

Oh, Scorp 508, there's someone here to see you.... :D

 

... :lolg: :rofl: :lol: ...

 

It seems like it only runs under no load.

Perhaps your TV (throttle valve) cable needs to be adjusted. Do you have the factory service manual, by chance?

Also, what year is your vette? All the overdrives units operate differently from 84 to 88.


[Modified by CentralCoaster, 1:57 AM 7/25/2003]

 

Other than a Chilton and a Haynes I have no other manuals. Also it is an '87

 

check the fliud level first, get under the car and on the L side of the OD section is a plug, the level should be up to that level..

 

Have changed oil and brought it up to correct level with no effect. Thanks

 

Howdy Neighbor! I'm in Vancouver, too. 85 4+3 also, but I don't know much about your problem, just thought I would say Hi!

Kirk :seeya

 

I have one question first: Does the "overdrive" light on the dash light up as it should when you hit the switch? or does it come on when the overdrive comes on?

You should also do some more op-tests to see what's behaving properly and what's not to narrow it down. I don't recall the website, but it lists all the conditions that the ECM controls it under.

Also, try taking the car up to 110 mph (~105ish for 86-on) and the computer should engage overdrive despite all the other inputs.


The computer activates the solenoid to turn the od on/off based on TPS, and the first gear switch, and other gear switches (depending on your year). It also turns on the light on the dashboard. The fluid pressure in the unit must be ~75 psi to allow the signal to the solenoid. As far as the electrical side goes, this appears to be the only way the dash light would go on without the overdrive actually engaging.

Maybe your problem is mechanical. The book says the solenoid causes the shift valve to change the fluid flow paths, which causes it to run in overdrive. If the shift valve is hung up or has debris in it, it might not be moving freely. I'd still want to check the tv cable though. The book doesn't say much about it, but it's a standard item on any automatic. I don't know if it's adjustable without dropping the o/d pan or not. You'll need to drop the pan to get to the valve body, it's pretty easy and you can do it all with the tranny in the car.

I'd want to find someone else with this exact problem before touching it though.

Good luck. :cheers:

 

Thanks for the info.It's more than I have gotten from any of the Chevrolet dealers in the Portland-Vancouver area. I have been stunned by how little they know about Corvettes.

Anyway, I do get an o'drive light when I press the button,but activation only when I back off the throttle from a steady cruise RPM. Thanks again