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89 and 91 GT wire harness differences?

New User
Posts: 1
Joined: 07/09
Posted: 09/13/09 07:33 PM

Hey guys, I'm new to the forum and have a tech question about my 89GT. I bought an 89 chassis without the motor, AOD, ECU, and engine harness. I bought a wrecked 91 GT for parts, I.E. engine, 5-speed, ECU, and engine harness. So I'm putting the 91 running gear into the 89, and have the following questions:

1. I have noticed one difference so far in the wiring harness under the hood, driver side near the firewall/master cylinder, the 89 has 1 black and 1 grey semi-circular connector, both have 8 wires. The 91 has an orange semi-circular connector with 8 wires, and no second connector. I have only partially traced out some of the wires using color codes from charts in the haynes manual. This finally leads me to my first question: should I just swap the whole chassis and engine harness from the 91 to the 89? Or do any of you experts know exactly what the differences are between 89(with AOD) and 91(with 5-speed)? I need this to be smog legal, so no check engine lights will be acceptable.

2. Obviously I need to hack a larger hole in the floor for the 5-speed, right?
3. The 89 has no air bag, but the 91 does. If I end up having to swap the 91 harness to the 89, will the lack of an air bag in the 89 affect anything?

Thanks guys!  

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New User
Posts: 1
Joined: 11/09
Posted: 11/03/09 02:39 PM


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New User
Posts: 1
Joined: 01/14
Posted: 01/27/14 01:54 PM

I'm having almost the same problem I have a 1990 wiring harness I'm trying to put in a 89 did you ever figure it out??  

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Posts: 65
Joined: 10/13
Posted: 01/27/14 08:23 PM

this kind of swap requires a set of factory wiring diagrams and the factory service manual to see where everything hooks up..

autozone dot com has the basic engine control diagrams .. on their repair info site..

you can get them online thru alldatadiy dot com or eautorepair dot net

there are also manual suppliers like Helm.. or used ones at faxonautoliturature.

there is a few hundred dollars in print..


there is just a LOT of stuff to get it right..  

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