why would the overdrive gear just quit suddenly? for the last few months it has been shifting consistently at 38mph into 4th.. no problem.. then suddenly not. the light on the dash illuminates on/off when the o/d button on the shifter is depressed. relay is clicking. no 11 fuse has power. any ideas???
trans oil was changed a few months ago for the same issue. mech had to blow out fluid from the (new) solenoid to get it working but then has performed w/ no problems.

 

I recently had a similar problem on my 1990 240DL, but mine began with the overdrive operating intermittently. There's a solenoid mounted to the top of the transmission that either allows or restricts overdrive. My wiring to the solenoid was OK. Instead of replacing the solenoid I went with an overdrive bypass plate from IPDUSA. With the bypass plate, overdrive lockout is unavailable.

 

thanks i was thinking that also as a solution if the solenoid was not working. but it was installed new and working for a few months so ... ?? i don't give a rats *** about turning off overdrive i want/need it all the time...

 

the OD solenoid can get clogged up with a tiny bit of flug in your ATF, and stop working, or the OD hydraulic circuit inside the transmission can get a bit of debris/dirt in it and clog up and stop working.

the solenoid has to be powered to enable OD, when its powered, the valve in the solenoid opens, and allows ATF to flow into the OD control pistons. note that when the OD light is ON, the OD solenoid is OFF, and when the light is OFF, the solenoid is ON (backwards, I know)

I've heard of people fixing it by removing the solenoid and cleaning out the fluid ports in the transmission. sometimes simply flushing and changing the ATF will fix it (ATF Is a strong cleaner, and fresh ATF can dissolve a fair amount of some sorts of debris).

if your OD solenoid was changed a few months ago, its probably worth double checking that the wire is still connected... no wire == no juice == no OD. the light will still toggle.

 

I will keep this simple to start with and see what the response is.

You need to go under the car, unplug the single wire to the OD solenoid and see if it has 12v to it. I am giving up on teaching the ways of the multimeter. I suggest you get a test light.

 

This is the order in which I check things when OD isn't working:

1) Check the relay. If it doesn't click when pressing the button then it probably has cracked solder joints

2) Check the wire running to the solenoid on the transmission. You have to go underneath for this. Every 240 I have had the insulation cracked off and I had to splice new wire in.

3) Check the solenoid itself

I've never had to replace the solenoid yet but my cars are all between 225 & 250 k miles

 

I have an OD bypass that I can sell you if you're in the states. Brand new from IPD

 

thanks all responses. i can't get underneath enough to check the wire to the solenoid (no jackstands /proper jack) so i will have my indy check when he does the rear brakes tomorrow.
i tried with the my test light & meter to check all i could from above but everything had juice.
will post result.

 

bahh, the o/d self healed ... the question is why? my indy indicated that if the wire down to the solenoid was chafing etc it would pop the fuse... but the fuse never popped. maybe gunk in the passages worked its way out? or maybe the relay... which seemed to work and click etc was making some kind of intermittant contact? a mystery ..

 

Mine temporarily "self-healed", also. The remission was short-lived and patient required surgery to remove the malignancy. Hope you have better luck.

 

well it un self-healed turned out the relay was bad, but only cutting out when it got hot. thus the mystery.. i have pin 15 and 87 jumpered with a paper clip so the o/d works until i can get a new relay.