Quick question: AOD to T5 swap

trents99 · Dec 6, 2005

A friend of mine swapped a T5 into his 89GT and has been having issues with the computer. He got the donor computer from the same 5 speed car that ran fine before everything was pulled out. I've heard there is a wire from the computer that is supposed to have been cut or bypassed or looped together but can't find any write ups that explain this. Anybody know what wire this is?

srothfuss · Dec 6, 2005

There was a guy (it's posted in talk) that has the write up in a magazine. I'll see if I can find the thread.

Here you go: http://forums.stangnet.com/showthread.php?t=598561

Bladez5_0 · Dec 6, 2005

I never had to cut/bypass any wiring when I did my swap but I had the wiring harness from my car too. What kind of problems is he having? Does he have the clutch relay hooked up or jumpered like it was for the AOD? Is he using the T5 wiring harness? Little more info would be helpful.

trents99 · Dec 6, 2005

Well he asked two different people that had done the swap and they told him two different things. One said cut the wire on pin 30 which goes to the ign switch, neutral safety switch. Another guy told him to cut the wire from pin 46 which looks like a ground signal to most of the engine sensors. I told him I'd cut 30 before 46 and he did. He got all the parts off a donor car but kept the AOD harness. He's only running the wires from the VSS and the one on the side (can't remember it's function other than back up lights). He has no neutral saftey plug.

Problems are that it's hard to start and often dies while in neutral or low speeds. He said as he is driving down the road it is fine. I know the VSS can affect neutral idle sometimes.

Another issue that happened right after the swap and which I thought was the root cause of this is his TPS now reads 5v on all three wires. We swapped on my TPS and it still read 5v. I'm thinking maybe it is grounding out somewhere in the harness possibly???

gregpro50 · Dec 6, 2005

You shouldnt have to cut any wires at all. It is basically a straight-forward swap. I just did it in my '90 GT vert. You dont need to change computers. The aod one will work just fine. Also the neutral safety wire doesnt need to be cut. I think you may have gotten some bad info.

04sleeper · Dec 6, 2005

I didn't cut any wires when I did mine. Woked just fine.

trents99 · Dec 6, 2005

All right thanks guys. I'll pass the info along to him.

wht93gtEd · Dec 6, 2005

gregpro50 said:
You shouldnt have to cut any wires at all. It is basically a straight-forward swap. I just did it in my '90 GT vert. You dont need to change computers. The aod one will work just fine. Also the neutral safety wire doesnt need to be cut. I think you may have gotten some bad info.

:Word:

A car that was originally equipped with an AOD (A9P) can't run a 5spd computer (A9L) because of wiring differences in the harnesses.

The AOD computer and 5 spd computer are essentially the same except the AOD has a lower rev limiter but it doesn't retard the timing when you shift

Just stick with the AOD comp...I've been running it for over a year in my 5spd car.

Curse · Dec 6, 2005

wht93gtEd said:
:Word:

A car that was originally equipped with an AOD (A9P) can't run a 5spd computer (A9L) because of wiring differences in the harnesses.

The AOD computer and 5 spd computer are essentially the same except the AOD has a lower rev limiter but it doesn't retard the timing when you shift

Just stick with the AOD comp...I've been running it for over a year in my 5spd car.

I remember when I was looking into do the 5 speed swap, I read that running the AOD comp. was better than switching to the 5 speed comp. Any truth to that?

Red00vert · Dec 6, 2005

Trent is talking about me. If I reconnect the #30 pin wire and use a c3w computer will that work? Is there a difference in c3w and a9p? Any other question about my car? I really need to get these issue resolved.

jwzg · Dec 7, 2005

First, you can use the A9P (AT computer) with the manual tranny. As a matter of fact, the timing is a little more agressive on the A9P, but the rev limiter and everything else is the same. The whole problem with running the 5 sp. (C3W, X3Z et al) computer on an AOD harness is because pin 30 of the AOD harness is wired to the starter solenoid instead of the neutral drive switch as it is on the MT harness. There is a diode on the AT computer that suppresses the voltage spike that occurs at start up, but that diode is missing on the MT computer. In a prolonged cranking situation, that voltage spike can and will fry the MT EEC. If you disconnect that wire at the solenoid and run it to the neutral drive switch on the T5 (as it should be in the conversion), you can run the MT computer, but given the slight advantage of the A9P over the MT computers, I would just forget it and run the A9P. By the way, if the wire to pin 30 is cut, you cannot pull codes. Food for thought if you need to diagnose any ills.

Credit to tmoss for the explanation.

Good luck!

mike0227 · Dec 14, 2005

The C3W is an automatic computer according to what I have read? I converted my auto to a 5spd and run the c3w however, I cannot pull codes codes.

blackcloud50 · Dec 14, 2005

mike0227 said:
The C3W is an automatic computer according to what I have read? I converted my auto to a 5spd and run the c3w however, I cannot pull codes codes.

You mean that you can't run the KOER?

Quick question: AOD to T5 swap

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