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1985 740GLE overdrive woes

Good day,

I have a 1985 740 GLE with an M46 manual transmission with overdrive.

Overdrive acts flakey.

At normal to high temps, the overdrive can be engaged shortly after hitting the road. The warme it is, the quicker it engages.

At low temps, it takes quite a while but it does eventually engage.

I have eliminated the switch on the gear selector (shifter).

I have opened up the relay and cleaned the coil contacts.

I have checked the terminations at the solenoid.

I addition, if I move the gear selector to the left a bit, the overdrive will disengage leading me to believe that there are 2 problems; one with the 4th gear switch and something somewhere else.

I see on the schematic, that the EGR solenoid is in the same circuit but I figure that it's just drawing power from the same place as the relay circuit.

Where exactly is the 4th gear switch? Under the console? Can it be adjusted? Can I reach it without pulling the console?

I have pulled the top cover of the console off, but never the shifter boot.

Any ideas on the overall problem?

I don't really want to "diagnose by replacement" the solenoid as it is pricey.

Could this be a problem with the transmission oil? Drain and change?

TIA

regards

jimB

-------------------------------------------- JimB

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Reply to
jimb
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On Sat, 21 Jan 2006 12:11:47 -0500, jimb wrote: Oh I forgot, relay does not click until the overdrive is ready to engage. That is, until car warms up, no relay noise.

jimB

-------------------------------------------- JimB

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Reply to
jimb

replace the OD switch on the gearbox. I think they can get contaminated with oil which makes them sluggish with cold.

Reply to
M-gineering

My 240 has this exact same set of problems, it's the 4th gear switch on the side of the transmission housing. It gets worn and will prevent the overdrive from engaging until it warms up because it thinks the car is not in 4th gear.

Reply to
James Sweet

Is that the 4th gear switch? It's on the gearbox?

I am glad I didn't rip out the console.

jimB

-------------------------------------------- JimB

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Reply to
jimb

rh side of the gearboxcover (the other one is for reversing lights). Resist the temptation to bypass the switch, as it will then be possible to engage first gear and reverse with the OD switched on, which is not_a_good_thing

Reply to
M-gineering

no it would not.

thanks much

jimB

-------------------------------------------- JimB

-------------------------------------------- my SPAM defense: Replace all the X's in email address with M

Reply to
jimb

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