Engine & Tranny Swap

Ten30 · Feb 14, 2007

I'll try and make this quick. I have a '91 XJ with a 4.0L and aw4 tranny, and a '88 with a 4.0L and a Manual. I want to swap the '91 Motor and tranny into the '88 but my Mechanic is telling me that we can swap the motor but not the tranny because the computer will through a check engine light on. He is telling me that the computer will not recognize the new tranny. Is there any truth in what he is saying.

From what I understand:

#1- ECM's will NOT direct swap. but the only sensor the ECM monitors is the VSS, and that can be tricked somehow.

#2- Every part on my 88 should fit directly onto the 92 HO motor. so it should be an easy swap .

But I still don't know if I can use the AX4 in the '88, and if I can how.

- any help would be greatly appreciated.

Thanks

Bouncy · Feb 14, 2007

As far as I know. All the Aw4s are the same. The 92 and up had a different tranny controler and the 96 and up again another tranny controler. But as far as I know...ALL aw4s are the same.

Well almost all, thinking again...There are 21 and 23 spline models. The 91 and older are 21 spline and 92 and newer are 23 spline output to the t-case.

So if you swap a newer motor and tranny, make sure you have the t-case to support it.

lawsoncl · Feb 15, 2007

The AW4 had some sensor changes with change in 96. You can use a post 96 AW4 in an older XJ if you pull the tailcone and swap the speed sensor rotor. That's not needed in this case as the 89 and 91 are the same. There is the possiblity of a spline count difference since 91 was a bit of a tranistion year.

You are correct that the ECMs will not directly swap, which is fine because you don't need to. As far as controlling the tranny, you only need to grab the trans computer located under the passenger lower dash, the wiring harness leading down to the tranny and as much of the wiring that goes into the harness as possible from the 91. You'll probably need an FSM to help figure out splicing in the power, brake switch, etc. You'll need to find the automatic version of the TPS sensor for an 89 as it has a second connector to provide the throttle position signal to the TCU. On the 91, this signal comes from the engine computer.

Ten30 · Feb 15, 2007

lawsoncl said:
You are correct that the ECMs will not directly swap, which is fine because you don't need to. As far as controlling the tranny, you only need to grab the trans computer located under the passenger lower dash, the wiring harness leading down to the tranny and as much of the wiring that goes into the harness as possible from the 91. You'll probably need an FSM to help figure out splicing in the power, brake switch, etc. You'll need to find the automatic version of the TPS sensor for an 89 as it has a second connector to provide the throttle position signal to the TCU. On the 91, this signal comes from the engine computer.

OK so The AW4 will work but with allot of work? how much of the wiring will I need form the Tranny computer out of the '91, and will it plug into the harness on the '88 or will I need to splice it in? Will the Trans computer work with the '88 if I get a TPS off a '88 with a auto? I guess the real question is... Is it worth it?

Ten30 · Feb 15, 2007

WOODBUTCHER said:
The TCU is the transmission computer since the AW4 is electronically controlled.

On a 91, it would be under the dash on the passenger side. There are two studs on the kick panel where it would normally attach. You'll probably want access to a donor to get everything you need. Grab the controller and as much of the wiring harness as you can. Most of the wires coming from the TCU go to the tranny wiring harness for the solenoids, NSS, and output shaft speed sensor. The rest of the wires are for the TPS sensor input, battery +12v, ign 12 volt, cruise/power switch, brake switch, and the diagnostic lines (don't really need to hookup).

Your 91 is an HO and not the older Renix? The Renix setup used a TPS sensor with dual outputs to feed a signal to both the engine and tranny computer. The HO setup has the engine computer relaying a signal to the TCU. You may have to swap the ECU to an automatic version as the manual ECU may not have the TPS output. The wiring isn't bad if you have a FSM handy with the wire colors. Alternatively, you can look at using one of Brett ideas to go manumatic instead of using the TCU at awshifting.com

On the NSS, you'll need to hookup the reverse lights and optionally the neutral starter lockout (I'd recommend it, though). You'll also need the shifter, shifter cable, tranny-throttle cable, the longer xfer case linkage, etc. You'll want to redrill the holes in the body bracket that holds the cfer case linkage 2" further forward as the linkage rod is 3" longer and the tranny is 1" longer.

Also, you want to try to use the same year TCU as the AW4. You can use different years, but you can't cross the 1996/1997 year as a few sensors on the tranny changed with the switch to
this is what I found
Sean

I just saw this on another post: So has any one done this swap and how much work is it, Really? I be willing to "donate" the AX-15 to any one that wants to help me with the swap.

I own the '91 and it just got totaled, so I can take as much or as little as I want off of it.

Engine & Tranny Swap

Ten30

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Bouncy

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lawsoncl

NAXJA Forum User

Ten30

NAXJA Forum User

Ten30

NAXJA Forum User

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