Hi,
I have an 89 740 GL with the AW70L transmission. The overdrive engages smoothly, and always goes in around 40 mph. The problem is that when I hit the switch on the side of the shifter, nothing happens. There are times I really wish I could disengage the OD, like when going down hills or merging onto the highway. I hear about overdrive failure a lot but mine works fine, just want to figure out if I need a switch or something else?
Thanks!

 

the dashboard light doesn't toggle with the switch? then odds are, the wiring to the button on the shifter is kaput. its hard to fix that wiring as its inside the shifter handle

its also possible the OD relay is stuck. the circuit is a bit odd, when the light is OUT, the OD enable solenoid (on the transmission) is powered, and when the light is ON, the solenoid is de-powered.


alternative: someone before you modified it to permanently enable OD because the wiring was broken. this can be done via replacing the solenoid with a little brass plate kit that IPD sells, or by grinding a notch in the end of the solenoid plunger.