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Overdrive problems

It's on the passenger (right) side close to the bell housing.

Pigtail.jpg
 
Thank You sir, I'm guessing I can't get to it through the interior shifter area, that would be too easy.
 
Nice. Will it let fluid out?...sorry this is something I've never dealt with. OD hasn't work for quite some time now but I m driving freeways more so I gotta' get it sorted. I'll get this replaced and then I'll replace the shifter knob switch and check all the associated wires for wear. I guess there isn't an OD relay on this car, or at least that's what IPD said over the phone, 'cause they don't have a OD relay on their website???
 
No fluid will come out. The switch is well above the fluid level.

A '90 740 w/M46 should use this yellow overdrive relay part #3523806. iPd doesn't have it listed on their site.

3523806_1.jpg
 
Before firing the parts cannon, why not find out what's wrong.

It doesn't make a lot of sense to me to start buying electrical parts if the O/D itself won't work.

Have your tried to bypass the wiring and test the O/D directly? It isn't very hard to do.
 
Before firing the parts cannon, why not find out what's wrong.
It doesn't make a lot of sense to me to start buying electrical parts if the O/D itself won't work. Have your tried to bypass the wiring and test the O/D directly? It isn't very hard to do.

"parts cannon" that's great I may steel that. In this case admittedly I'm more comfortable with replacing these little parts over troubleshooting. I have not bypassed the wiring to test the OD directly.....I will do a search for that as advised and figure it out or you could explain that to me, much appreciated.
 
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I had severely damaged wires up there once, no insulation on them and randomly touching stuff. I hosed it all down with brake cleaner than used liquid electrical tape to re-insulate them. Hack job for sure but it worked until I sourced a new harness.
 


Also seen here, next to the crimping tool under the rubber boot covering the wiring. On 1981-on cars, it's just a single wire with a female bullet terminal. You'll need a 3/8" deep-well 7/8" or 22mm socket on ideally a long handled ratchet to get it out.

Relays can be flaky too.

Is it just not working when cold, unless you hold the shifter as far back and to the right as possible? Or, is it flaking out when warm? If the former, then it's likely the switch. If the latter, then it may be the solenoid losing pressure, either due to leaks, bad fluid, or it failing electrically. Right now, your old wagon works fine when cold, overdrive-wise, but begins slipping into overdrive when fully hot. Sometimes will do a false neutral. Suspecting the speedo gear seals, since, when the cable was disconnected from the gear housing, some fluid came out. Probably going to do a fluid change and, while I'm at it, change the seals on the speedo gear housing.
 
No fluid will come out. The switch is well above the fluid level.

A '90 740 w/M46 should use this yellow overdrive relay part #3523806. iPd doesn't have it listed on their site.

<snip>

Ian, it may also use the older 1347768 red relay. It won't use the black or blue 1259750 relay, though, at least without some slight rewiring of the harness plug. I've done that in a pinch on a couple '85 240 cars.

Lately, I've just switched to the pre-'81 setup, as shown in the OP's old 245 here:



*edit* I'm closer to him... Have an '80 box with a rebuilt overdrive in my garage.

-J
 
For some reason I was thinking it would be a red square relay but the only red-ish one in there is the round bulb failure one. There is a yellow square one in there, that's got to be the ticket.
I will gain full access to the relay board in the morning. Thanks to all you guys for the input so far.
 
PM me with the relay part # tomorrow morning to remind me to look, I'm scrapping my 91 740 T and probably have a good one in the car still.
 
For some reason I was thinking it would be a red square relay but the only red-ish one in there is the round bulb failure one. There is a yellow square one in there, that's got to be the ticket.
I will gain full access to the relay board in the morning. Thanks to all you guys for the input so far.


If your 740 is a wagon, the yellow relay may be the rear wiper relay.
 
Lol fine. Diesel? It's from a 740T

The turbo boxes are based off the Diesel transmission. Same gearing, same weak internals. lol Even the 1983 and newer non-turbo boxes use the same crappy transmission design, which, while better than a M47, is not much better than one. Hence one of the reasons why people keep blowing them up.
 
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