help putting the overdrive back to my control

[bad87vette]

Hi everyone,
You guys are awsome very helpfull and very professional I recently purchased
an 87 the problem is the previous owner install one of those aftermarket
chrome shifter knobs. There is no switch on the top of the knob but yet the
overdrive still works. It automatically kicks in when I accelerate or kicks out when downshifting or slowing down. I want to install back the original knob to where I can control when to enable and disable the overdrive. Folks I need your help on how to get the overdrive back to its original form. I'm curious
how the heck does it know when to disable during deceleration can the ECM
do this or is there a aftermarket modules that can automatically
enable/disable the overdrive. Your help is greatly appreciated many thanks to all.

 

[mmark2]

Hi everyone,
You guys are awsome very helpfull and very professional I recently purchased
an 87 the problem is the previous owner install one of those aftermarket
chrome shifter knobs. There is no switch on the top of the knob but yet the
overdrive still works. It automatically kicks in when I accelerate or kicks out when downshifting or slowing down. I want to install back the original knob to where I can control when to enable and disable the overdrive. Folks I need your help on how to get the overdrive back to its original form. I'm curious
how the heck does it know when to disable during deceleration can the ECM
do this or is there a aftermarket modules that can automatically
enable/disable the overdrive. Your help is greatly appreciated many thanks to all.

To the top.

 

[c4cruiser]

The 4+3 trannies operated differently from year to year. This website: http://www.5speeds.com/dne.htm has some good info on unit repair and how they operate. Click on the link "Click Here to see our OD comaprison chart" to find out how the different years operated.

You can find the answer to your question on OD operation in the table for the 87-88 tranny.

The chances are that the prior owner simply connected the wires in the shift handle together when he installed the new knob. There is a microswitch in the factory knob that overrode the ECM operation of the OD unit. Mid-America has a replacement knob and button (go to www.mamotersports.com and enter part number 611-626 for info.

I don't have a source for the switch, but I recall other owners of the 4+3 trannies using a microswitch from Radio Shack. Might have to do some searching or call the number on the 5speeds website to see if they can help.