# 91 sentra with 4 speed automatic transmission wiring



## rustybutterknife (Sep 26, 2011)

I have a 91 sentra that came with a 3 speed auto. We are switching it over to the 4 speed auto. So far we have the mounting, selector cable, and speedo figured out but there's still one more thing to do but I'm not quite sure what to do about it. The 4 speed has 3 wires comming out of it they are red, blue, and black. I can't seem to find anything in diagrams that will tell me what these wires do or go to. I am assuming for now that they are for the overdrive system, (hope they're not evidence of an electronic shift governing system) in which case I'd be cool with wiring it to always be in overdrive mode. But i want to be sure and I was hoping someone may be able to point me in the right direction to finding info. on this system and how it works.


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## jdg (Aug 27, 2009)

Probably lockup solenoids *AND* overdrive solenoids.
And wiring it to always be in overdrive? Ya that'll work...'till you need to stop, slow down, or start from a stop. Other than those 3 conditions, I'd bet it would work fine.
But, as always, without any sort of designator, transmission ID, etc, origin of this particular transmission, those red, blue and black wires may as well be pretty pieces of yarn hanging from the output bearings.


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## smj999smj (Jan 1, 2006)

Nissan wiring diagrams use the color of the wires of the main harness and not the wire colors of the wires from the specific componant. I mention this because I think you may be refering to the three wire connector for the lockup solenoid and overdrive cancel solenoid. The wires listed in the diagram per the Nissan diagram are pink/black, black/yellow and, depending on application, either yellow or white/green. If you want, E-mail me at [email protected] and put "RE: 91 Sentra AT wiring diagram" in the subject line and I'll send the diagram to you.


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## rustybutterknife (Sep 26, 2011)

jdg said:


> Probably lockup solenoids *AND* overdrive solenoids.
> And wiring it to always be in overdrive? Ya that'll work...'till you need to stop, slow down, or start from a stop. Other than those 3 conditions, I'd bet it would work fine.
> But, as always, without any sort of designator, transmission ID, etc, origin of this particular transmission, those red, blue and black wires may as well be pretty pieces of yarn hanging from the output bearings.


My understanding of this is limited for sure. When I said I would wire it to be in overdrive all the time what I meant was overdrive mode as to simulate the button on the shift lever being left on like you would have it set for normal driving, NOT wire the transmission to run in the overdrive gear at all times. If that is what I would be essentially doing, I at least know enough to agree that it would be stupid to do that. I will rewire the vehicle and do a full conversion with every stinkin' piece if I have to before I will half ass it to that degree.
It is a 4 speed automatic out of a 95 ? sentra with a 1.6 engine. Not sure where to look for an ID # but I took a couple of photos.








Left side wheel well








better view of where the wires go in








top side 

@ smj999smj, I sent you an e-mail.


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## smj999smj (Jan 1, 2006)

Info sent.


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## djah (Feb 24, 2009)

Hey guys,
Sorry for hijacking your thread but I am looking for a little help please.
Yesterday my transmission developed a problem and will not shift beyond 1st.I have just gone through the process of changing the fluid and filter in the hope that this might cure the problem but it did not.Would you have any suggestions as to where I should focus.Could the speed sensor be at fault or is there even one fitted (showing my ignorance here).Its a 93 sentra or sunny as is what they were sold as here in Ireland.
Thanks.


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## smj999smj (Jan 1, 2006)

If you have a 3-spd. AT, check the governor gear. They would strip and not allow the trans to shift out of 1st gear. Looking at the top of the trans, you'll see a large, black plastic cap held on with a spring clip. IIRC, remove the cap and the retaining bolt on the side of the trans and pull the governor assy. upward and out to remove and inspect the gear. Some were made out of plastic and later updated to a metal gear. If you don't have the 3 speed AT, let us know and provide us with more info.


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## djah (Feb 24, 2009)

Thank you very much for your response.
I am very sure that it is a 4sp AT that I have.Last night I removed and inspected the governor and as you described the governor gear is stripped.I have just e-mailed Macko Transmissions as they have the part listed on their website.Hopefully they will be able to mail it to me.I am living in Ireland and I hope this wont prevent them from mailing it.The alternative would be the scrapyard as the cost of a replacement transmission is just too much.
Thanks again for your help.


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## jdg (Aug 27, 2009)

:cheers: Damn SMJ! Good call! +1 :cheers:


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## djah (Feb 24, 2009)

Part arrived this morning,fitted it this afternoon,back motoring again.
Thanks smj for your help.

Just a tip for anyone:
I was able to get the cover off the governor housing with a strong magnet just by attaching it and wriggling it over and back.


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