4+3 Overdrive out
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Instructor
Joined: Oct 2001
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From: Walnut Creek CA
4+3 Overdrive out
Not sure how serious a problem I have. Started driving to work this morning, and when I hit 2nd gear, the OD light did not come on as usual. Tried to turn it on with the switch on the gearshift, no luck. Same problem with 3rd and 4th. Did I just blow the fuse for the OD, or is there a more sinister problem? Any ideas? I think it might be the fuse because I noticed the console light that shines down from the rear view mirror was out, could they be in the same fuse? everything else seems to be ok... Had no time to check the fuses, and drove the truck to work instead.
Instructor
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From: Dead center of Seoul
Re: 4+3 Overdrive out (mt_789)
Might be a fuse...might also be the overdrive switch itself. I'm not positive where it is (connects to the OD button on shifter). My OD had the same symptoms, had the switch changed, problem solved.
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Instructor
Joined: Oct 2001
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From: Walnut Creek CA
Re: 4+3 Overdrive out (ZylaRace)
It is an 88. If the swich went bad, would it completely knock out the overdrive? I guess I will find out when I get home if a fuse blew ( I hope so)
Team Owner
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From: Boston, MA
Re: 4+3 Overdrive out (mt_789)
If the switch was dead, the OD would still activate and the light on the dashboard would come on. Your '88 has the identical program to my '87 (the only two years that do).
I would test the overdrive relay in the engine compartment to see if it has gone bad. I had a loose wire in mine cause this condition before. Then I would hit a bump and it would engage. A real pain. :)
[Modified by scorp508, 5:07 PM 2/14/2002]
I would test the overdrive relay in the engine compartment to see if it has gone bad. I had a loose wire in mine cause this condition before. Then I would hit a bump and it would engage. A real pain. :)
[Modified by scorp508, 5:07 PM 2/14/2002]
Drifting
Joined: Mar 2000
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From: Woodstock GA
Re: 4+3 Overdrive out (mt_789)
You might have to get a hold of a scanner and take a look you could have a number of problems on of which could be that first gear switch if the ECM thinks the car is still in first it will not turn the O/D on. The relay has nothing to do with the LCD O/D light unlike the 84 to 86 if the O/D does not come on it's because the ECM is not turning it on so there is were you need to start. Unplugging the first gear switch should siginal the ECM that the car is not in first so try this and see if the O/D comes on. If it still does not come on you would have to get a scan tool and check data to make sure coolant temp is correct and also TPS is working correctly if everything looks good you may have a problem with the ECM. Now if the O/D light up in the LCD and the O/D does not work then I would check the relay, but with out the O/D light in the LCD you need to fine out why the ECM is not turning it on.
David Fulcher
David Fulcher
Melting Slicks
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From: Lockport NY
Re: 4+3 Overdrive out (Dave's_88)
I'm not positive where it is (connects to the OD button on shifter)...
The switch itself only costs about ~$12 from Newark Electronics (www.newark.com), or ~$70 from various aftermarket sources...
The part #'s are 61F752 (1985 On/Off) and 61F753 (1986+ Momentary Contact).
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Thread Starter
Instructor
Joined: Oct 2001
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From: Walnut Creek CA
Re: 4+3 Overdrive out (scorp508)
Thanks everyone for your help. It looks like I have my work cut out for me! And I was counting on just a burned out fuse! I should know better...
Melting Slicks
Joined: Sep 2000
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Re: 4+3 Overdrive out (mt_789)
Hey where is this relay that you guys are talking about? My 4+3 would never engage, but the switch would activate and deactivate the little D on the gauges just fine.
Probably my problem is a sick sick OD unit (we'll find out soon when we crack it open) but it would be nice to have some ideas just incase for when it's all rebuilt and still doesn't work :D <knock on wood>
Probably my problem is a sick sick OD unit (we'll find out soon when we crack it open) but it would be nice to have some ideas just incase for when it's all rebuilt and still doesn't work :D <knock on wood>
Melting Slicks
Joined: Aug 2001
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From: Lockport NY
Re: 4+3 Overdrive out (scorp508)
These seem to go bad pretty often (coff *Scorp* coff),
I know not what you speak of. :jester
I know not what you speak of. :jester
Instructor
Joined: Dec 2001
Posts: 147
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From: Riverside CA
Re: 4+3 Overdrive out (mt_789)
You might want to check the WOT (wide open throttle) swich. This switch over-rides commands from the computer to shift the o/d unit.. If you accelerate hard in first it allows you to shift in direct all the way to 4th without going into o/d. If the switch goes bad it may be telling the computer that you are at wide open throttle position and keep the unit in o/d until about 120 mph where it will shift regardless of throttle position. Good Luck
Team Owner
Joined: Mar 2000
Posts: 83,383
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From: Boston, MA
Re: 4+3 Overdrive out (myblack864+3)
You might want to check the WOT (wide open throttle) swich. This switch over-rides commands from the computer to shift the o/d unit.. If you accelerate hard in first it allows you to shift in direct all the way to 4th without going into o/d. If the switch goes bad it may be telling the computer that you are at wide open throttle position and keep the unit in o/d until about 120 mph where it will shift regardless of throttle position. Good Luck
Instructor
Joined: Dec 2001
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From: Riverside CA
Re: 4+3 Overdrive out (David-F)
Sorry :smash: :smash: :smash:
I made a mistake in my last post about the WOT switch. Last line should read "it blocks the o/d until about 120 mph when the WOT command is overridden and the o/d kicks in. :seeya
I made a mistake in my last post about the WOT switch. Last line should read "it blocks the o/d until about 120 mph when the WOT command is overridden and the o/d kicks in. :seeya
- 1986 Original Owner -
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From: North Yorkshire, England
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Re: 4+3 Overdrive out (myblack864+3)
I'm with scorp here. Please enlighten us on the location of this mysterious WOT switch.
You might want to check the WOT (wide open throttle) swich. This switch over-rides commands from the computer to shift the o/d unit.. If you accelerate hard in first it allows you to shift in direct all the way to 4th without going into o/d. If the switch goes bad it may be telling the computer that you are at wide open throttle position and keep the unit in o/d until about 120 mph where it will shift regardless of throttle position. Good Luck
Team Owner
Joined: Mar 2000
Posts: 83,383
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From: Boston, MA
Last line should read "it blocks the o/d until about 120 mph when the WOT command is overridden and the o/d kicks in. :seeya
1985: 110mph
1986: 103mph
1987: 103mph
1988: 103mph
