As for the 90's the have an extrenal oil cooler, opposed to water oil cooler. Some of the 90 ecu's are eprom, to get a 90 ecu to work in a 91-94 you must switch around 2 pins(9 and 14 I believe). There cruise control is set up different. The coil packs are different, tach signal is different. The mph gauge is different, starts at 5 mph. Front axles have a slightly different design. Transfer case and Trans are different. The Throttle bodies are different and the wring for the TB and CAS are different. I think thats most of it.
If I reading your question right your wanting to swap your n/t motor into a gst shell? I'm not sure why you would want to do this.

noooo im swapping a 90's 4g63 turbo motor into a n/t shell and selling the n/t motor
ive already built up the gst motor, but im retaining my n/t wiring harness and doing like what was posted by mavaski in the " how to convert a n/t into a gst while keeping the n/t harness " thread and just adding the wires, but my n/t is a 93 and im thinkin this wouldnt work the same for the 90's motor. Would one think i should just go and buy a eprom ecu from a 93 and do they still sell those tihngs new any more??? and waht exactly does eprom do different, let you program more or somethin?

and what is different about the 90's model axles?? you mean as in cv axles. ( on a fwd)

If your swapping the 90 into the 93 then your better off using the 93 TB and CAS so you don't have to change the wiring. Your going to have to switch the 2 wires for the ecu. You also may have a problem with the tach signal, the wiring for the transistor is different from the 90 to the 91-94. Your going to need a wire going from the coil pack to the ecu pin 109, because the 91-94 have the wire coming from the transistor not the coil pack. Before you do this verify with wiring diagram and ecu pin out. I think theres a link on Jeff O's website that may help you, but that link tells you how to put a 1991+ in a 90 not the reverse, but it explains the differences and what you need for the tach signal. I hope some of that helps.

As the axles they just have a different boot design, nothing to be worried about.

i was wondering, since the transfer case is different, (i'm putting my 90 gsx motor and tranny into 92 tsi awd) should i buy the "newer transfer case or put my 90 driveshaft in the "newer" car or will this not work. thanks

carl5463729 said:

i was wondering, since the transfer case is different, (i'm putting my 90 gsx motor and tranny into 92 tsi awd) should i buy the "newer transfer case or put my 90 driveshaft in the "newer" car or will this not work. thanks

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The spline count is different on the transfer case on the 90's, so you need to use the 90 trans with a 90 T-case and vice versa. You could put the the 90 trans and transfer case in a 92.

ChicksDigBoost said:

If your swapping the 90 into the 93 then your better off using the 93 TB and CAS so you don't have to change the wiring. Your going to have to switch the 2 wires for the ecu. You also may have a problem with the tach signal, the wiring for the transistor is different from the 90 to the 91-94. Your going to need a wire going from the coil pack to the ecu pin 109, because the 91-94 have the wire coming from the transistor not the coil pack. Before you do this verify with wiring diagram and ecu pin out. I think theres a link on Jeff O's website that may help you, but that link tells you how to put a 1991+ in a 90 not the reverse, but it explains the differences and what you need for the tach signal. I hope some of that helps.

As the axles they just have a different boot design, nothing to be worried about.

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I just realized that is way more work than you have to do and I also forgot about the tach adapter on the 90's. You have a 93 coil pack and transistor already, so just use those. The 90 ecu will get the tach signal from the transistor and you should be all set to go, but you still need to switch the two pins 9 and 14, I believe.

ok what about this.... im going to put a 92 or 93 gst ecu in, and when i drop the 90s motor in im going to do away with the egr stuff or whatever stuff it has on it that differs the 90s motor from the 91-94 motor and just put the 91-94 stuff on there and keep my 93 harness already on there. therefore essentially it would be no different then swapping a 91-94 motor in right???
therefore from there ( correct me if im wrong ) but i need a 91-94 transitor, coilpack, cam angle sensor, ecu and throttle body???? correct? now remember i started with a n/t so will the coilpack off the n/t work? ( i know the cam angle sensor will from other posts that i put)
and also what is different about the throttle body ??? something i can go around or is the wiring different or something? or do you suggest i just put a throttle body from a 91-94 motor? and i dont understand the talk about the transistor?
I know thats a lot of questions but try to answer each question to best of your ability.. thanks1

and when you say throttle body it doesnt have anything to do with the intake manifold being different right? just specifically throttle body?

The manifolds are the same. The ports on the throttle body are different (see picture below), but you won't use the ports if you get rid of the emissions. As far as the wiring you can splice it in, the wires aren't different its just how they connect (see picture below, you can see the 2 connectors where the TB plugs into). If you use a 91-94 ecu, coil pack, and transistor you won't have any problems.

ok that makes sense well yea i think i will just do away with the 90s equipment,and put the 91-94 stuff that differs the two motors. itll be easier that way since i have a 93 harness anyways/