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Renix AW-4 Transmission Swap into a YJ
'87 XJ AW-4 into '93 YJ

By Shad Ahlstrom



Manual YJs have a pigtail near the transmission that supplies power to the reverse lights from a switch and provides a ground loopback for the starter relay.  I unplugged this connector and spliced the reverse light lead from the TCU.  I removed the loopback ground wire since I already spliced the start/neutral safety switch from the TCU to the YJs wiring harness.  I basically just activated the circuit by removing the loop.  I filled the extra holes with silicone and plugged the connector back together.


The Cherokee had a switch in it for POWER or COMFORT.  These are pretty vague terms but I knew they were related to transmission valve pressures and whatnot.  The switch applied +12V to the C11 pin of the TCU for POWER mode and 0V for COMFORT.  I unplugged the C11 pin from the TCU just to see the difference.  On my test drive, the 1-2 up shift point was dropped to about 1700RPM.  I didn't feel a 2-1 down shift but for all I know, there may not be one.  I didn't feel one in POWER mode either but it may just not be as pronounced as the 3-2 down shift.  I added a switch to the dash for good measure but I know I'll drive around most of the time with it in POWER mode.


I went to pick up the new driveshaft and it wasn't done yet.  That's fine, I wasn't in a huge hurry.  I was invited into the shop to watch the process.  I was so jealous of the tools in that place.  Roy put the shaft onto a lathe and ground the ends of the solid portion to spec.  He chopped the tube down to the right size on a cold saw.  I kept my distance for this part but there were some sparks and banging and the glow of a very large welder coming from the back of the shop.  He walked it over to me and it looked GREAT!  He popped it on his balancer.  This thing is monstrous!  It had to be 20ft long.  I only needed the first foot and a half of it.  He spun it up and it looked straight to me.  He rotated it to a certain point and used a torch on it and then immediately quenched it with water.  He did that about 5 more times and spun it up again.  He then added some weight to the front and back and a wire to hold it on.  After some adjustment of the weights, he welded them on and applied a coat of paint.  I didn't fully appreciate his attention to detail until I got it back on the Jeep and got it up to speed.  I've never felt such a smooth ride.  I'm sure my old shaft was out of balance from all the banging around on rocks.

So now I have an AW4, beefy driveshaft and a bulletproof rear end.  Everything is maintained, freshened up and in good shape.  I now have no idea where the weak point is in my drive train.  I hope it's not that crankshaft I nicked.




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