Overdrive Switch ?

time · Post by **time** » 02 Aug 2004, 16:26

I think my overdrive switch is bad. I can't turn my OD on or off. The OD off light goes on and off as it pleases. Also, OD will go on and off at speeds around 60 mph. Transmission changes smooth other than when it gears down at 60 mph. Is there a fuse or do I have to replace the switch? Or, could this be a bigger trans problem?

Thanks,
Nick

Mrkrinkle · Post by **Mrkrinkle** » 05 Aug 2004, 12:13

See the post I had about the same problem...a couple people answered.

csbrianp1 · Post by **csbrianp1** » 11 Aug 2004, 16:08

What model do you have?

TAFinley · Post by **TAFinley** » 17 Aug 2004, 10:19

Sounds like the overdrive relay to me. My '85 245GL eats one of those every 4 years or so. When it starts failing, it will switch itself into and out of overdrive at random times. Sometimes, I can give the dashboard a good whack and it will re-engage the relay.

On my model, it's located behind the dash to the left of the glovebox. It's relatively easy to replace. Just remove the glove box, find the relay (a little white or orange rectangular box), unclip it, remove the plug, plug in the new one, clip in the new one, then replace the glove box.

There is also a solenoid on the transmission (the part that actually engages the overdrive. Very expensive) that can fail, but once it does it's dead. You have the intermittent off/on problem, so it's almost certainly the relay.

TAFinley · Post by **TAFinley** » 17 Aug 2004, 15:04

Also, you should check the wire going to the overdrive solenoid on the transmission. If the insulation is frayed, you can get a similar intermittent problem.

You should do this before you spend money on a new relay.