98 aw4 into a renix?

so a 98 aw4 has become 'available'.... however i think i recall hearing the later model xjs controll the trans via the ecu, eliminating the Tcu.... or is this a pipe dream?

would this swap into a 90 xj 4.0?

Also there is a speed sensor change, then there is the 21 Vs 23 spline thing.

Pipe dream. The AW4 always had a seperate trans computer. It moved to the drivers side at some point which is why people think it went away. Anyway, the 98 tranny will bolt right up but you'll have some issues to deal with. I'm assuming you're starting with a 90 AW4 or are you swapping this into a manual?

- The output shaft will have 23 splines vice the 90's 21-spline. Not a problem if you have the AX15 manual, btw.

- The wiring harness connectors changed in 96, so you'll need to either cut&splice or drop the pan and swap over the older sensor and solenoid wiring harness.

- In 1998, a front input shaft speed sensor was added, which you can simply ignore, but the rear output speed sensor changed from 1-pulse/rev to 4-pulse/rev. Easiest solution is to pull the tailcone off and swap over the rotor and sensor from the older unit. You could try transplanting in a 1998 trans computer, in which case you'd need to figure out the TPS signal being backwards from what the 1990 TCU expects.

- The 98 AW4 had a different 4th gear ratio. 0.705 versus 0.75. Not a big deal.

i am starting with a 90 aw4.... so apparently this is a no go? due to output shaft spline count not matching?

If you have the T case that goes with the donor trans...

Or, you can even crack the t-case and swap the input on the t-case to 23 spline. Been there, done that. Not hard, just time consuming.

He'd still have to have a 23 spline T case to do that.