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740 m46 o/d wiring issues?

thelostartof

unbalanced chemical
300+ Club
Joined
Jun 26, 2002
Location
Apache Junction, AZ
Ok so I figured I would ask here before I dig to much into the car as I figure this is a fairly simple issue.

I picked up a 1991 745T (SE) that had been swapped from AW71 to m46. The OD worked the entire 200 mile back home. The car was wired in such a way that the dash light is always on and when you push the button for O/D the light goes off. I am 100% fine with this as it works, while it does allow you to use o/d in any gear that is not really the end of the world as this car just needs to pass emissions and be a backup car while I am working on other projects.

All of a sudden O/D has decided it wants to be a pain right when I go to emissions test the car.

In first gear I can push the button and the o/d light goes off most of the time, there are times I can push it and it will not go in or out of o/d even in first. All other gears the button does nothing. I removed the shifter and at first glance the wiring looks like typical m46 wiring.

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So I am guessing that the wiring from the shifter to the relay has issues because of age of the wiring this is why only is first gear the button works? So besides removing the shifter and the button and testing that the button works every time I am guessing that I just need to pull a new set of wires though the shifter and see if that resolves the issue right away? Is there a switch on m46's that allow it to only go into o/d in 4th? I have a spare m46 on the side of the shop I can check for spare parts (3rd gear is trashed on this trans).

Also does anyone have any tips on where to get the small spade connectors for the o/d button?

Thank you for your time trying to read my rambling, I am just trying to get a better idea on what I need to look at before I start tearing into the car so if anyone has any other key places to look for an issue like this let me know. Otherwise I am just going to wire up a switch on the dash for o/d and enjoy watching the idiots at the emissions test place try to go in and out of 5th with a dash mounted switch.
 
The overdrive relay works from the button on the shifter with a momentary pulse of twelve volts to change the state oif the relay. this is contolled by the suspected fourth gear switch. it is a single pin swtich on the top of the trans. The reverse lights is two pins so you know which one it is. The fourth gear switch provided ground for the relay to operate so if you aren't in fourth overdrive wont' work.

Your description of the light working the opposite almost has me wondering what someone did when they wired it in? It's supposed to be a blue relay and the automatic cars used a white relay. it's a straight forward circuit. Try to avoid using overdrive in the lower gears. It's not good for the unit.
 
Great info thanks, if I can find some time this afternoon I will check it out.

Funny thing is this car had an m47 in it first, but that trans ate itself so an m46 was swapped in. So I have all of the parts to swap it back to an m47, I just need to find a trans.
 
Great info thanks, if I can find some time this afternoon I will check it out.

Funny thing is this car had an m47 in it first, but that trans ate itself so an m46 was swapped in. So I have all of the parts to swap it back to an m47, I just need to find a trans.

Heard m46 way more durable than m47, rebuild the one you have in shop?

Wiring seems in reverse, autoboxes have the OD relay and wiring same as dl242gt described above.
 
Chances are the harness is broken where it comes out of the shifter and goes forward to the fuse/relay box. It makes a sharp bend there and gets flexed every time you shift.

Dave Barton sells a repro shifter harness and probably has the switch terminals as well.
 
You probably already know this but just in case... reverse is a no go with the overdrive on. That will kill the unit.
 
There is a roll pin or screws in the lower end of the lever. Remove them and just pull the lever straight up. Be carful. It may take some force to pull it up.
 
Better disconnect the reverse pull rod before yanking on the shifter or you're gonna break something.

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Ok this is going to be fun, it looks like the steel shifter is sticking into the chrome sleeve enough that I cannot just push new wires in there, so I am going to have to remove the entire shifter and possibly see all of those old failed bushings that I am going to want to replace.

Anyone have any recommend links for parts to use? Looks like parts # 7, 41, 40, and 23? what about 17 and 18?
 
I totally do not want to take it apart and put it together without new parts, and I need it to at least try to pass emissions today. So......there i fixed it for now until the parts I need to order come in.

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Damn can't believe they would test emissions on a thirty year old car. Even here in nj they stopped that silliness and only test 1995 and newer now.
 
Well the car passed the dyno test, failed evaporative. Ha, so I am going to change the tank seal and see how that goes. I already replaced a possible cracked hose at the charcoal can, idiot me should of checked that first. Nevermind they were clamping through wrong hose when test.
 
The car needs some love, and I have plans to ruin it for the time being while I work on fixing issues with it. Long term I want to white block and t5 swap it. Until then it might just sit and be a backup driver. I am going to remove the SE bumpers so I can keep them from getting worse and restore them over time.


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Nice. My white 744SE needs love too but I can’t let it go. Pics of Sbabbs’ minty one keep me going and also keep the SO a bit more chill

“I swear it CAN look like that”
 
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