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




That night I retraced all my wiring diagrams and decided it was related to the crankshaft position sensor.  I went back to the AX-15 flywheel and counted the teeth that trip the crankshaft position sensor.  I counted 3 sets of 4 gaps with the rest solid.  The XJ flexplate did not look like this.  It had a bunch of holes and gaps throughout the diameter.  I did a search online and found out that the RENIX system used a different flexplate than the OBD-I and OBD-II systems.  It didn't dawn on me until just then that the flexplate is an engine component, not a transmission component.  I borrowed a car and drove to Scotty's in Fresno and picked up a flexplate off a '95 Cherokee.  This one looked much better.  Mostly solid ring with 3 sets of 4 holes.  4 hours later, I had the new flexplate swapped in.  I turned the key and it fired right up!

I'm using the XJ's front driveshaft as a rear driveshaft but I'll need to shorten it.  I installed mounting plate to the flange on the 8.8 rear end.  I bolted in the CV end of the driveshaft to the yoke and held the shaft up to the side of the mounting flange.  I placed marks on the driveshaft at the front and back of the u-joint mounting hole.  Measuring from the center of the marks to the center of the front u-joint gave me the ride height length.  I had 15.5�.  I was almost directly lined up with the rear end so I didn't need too much room to compress.  I estimated about a half inch.  I added a quarter inch for good measure.  My new compressed measurements were 14.75�.  Since the XJ's front shaft measured well over 30�,  a pretty good chunk would have to be taken out.  I called OC Driveline and talked to Roy.  He told me that since I was planning on replacing the u-joints, I should do it now so he can get a better balance out of it.  He also told me to install the flange at the rear so it's complete when he gets his hands on it.  I had 3 sets of Super Strength Precision U-Joints with flush mount grease fittings in the cap ends(#280) and a u-joint/ball joint press ready to go.  I took the old u-joints off and inspected them.  They were rusty and a bit dry but still functional.  They could have been originals.  I popped the CV knuckle apart to inspect the parts inside.  This was my first CV joint so I was taking mental notes as I was going along.  The parts were pretty dry but functional.  The rubber was still intact and the needle bearings were in good shape after a cleaning.  I packed the needle bearings in with grease to hold them in place and slid the shaft in to check its movement.  It felt pretty good.  I separated it again and installed both u-joint crosses.  I pressed the hats on from the outside while holding the CV portion tight to compress the spring on the inside.  This is a pain in the butt!  There was probably an easier way to do this but I don't have this mastered yet.  Once everything was together, I installed the clips at the ends making sure that the shorter clips went in where the grease fittings were going to go.  Since I didn't have the right fitting for my grease gun yet, I squirted as much grease as would fit into the open hole with my small needle fitting.  I capped the hole with the flush mount fitting and that seemed to do an adequate job of pressing the grease in for now.  I tucked the end of my needle under the rubber boot inside the CV knuckle and packed it full of grease.  I spun the shaft around to the non-CV side and pressed out the u-joint.  I replaced this u-joint with the same style that went into the CV portion.  It wasn't necessary but it looked good and I'm starting to really like the idea of flush mount grease fittings.  As soon as I can find them in the right thread pitch, I may replace all the zerks around the jeep with these.  They look MUCH harder to snap off on a rock.

I popped the transfer case into 4 high and drove to the driveline shop which was about 10 miles away.  Driving only on the front axle is a very scary experience, especially in Southern California traffic.  This was my first real test of the Jeep.  The first thing I noticed was that the shift points were too high.  I was trying to gingerly drive the thing so I didn't screw up my front shaft or transfer case.  I gave the shop my specs and the driveshaft.  He was going to have it for me by the same time tomorrow.  On the way home, I hit some major traffic.  The engine and transmission got pretty toasty.  I could feel it through the clutch master hole in my firewall that I had yet to cap off.  Once I was past the freeway obstruction, I got into the throttle a little.  When I got up to about 70mph, smoke started pouring out the back of the Jeep.  I slowed down and got into the right lanes and the smoke stopped.  I followed some big trucks home so I didn't have to worry too much about my speed.  Once at home, I checked the transmission fluid level and it was a bit over full.  Strange.  I checked it cold before I left and it was barely on the add mark.  The transmission only had 8qts in it and to my knowledge held 9.5qts.  This was something other than too full I think.  Air bubbles in the lines?  Foaming in the transmission?  Don't know.  The vent tube was a little on the short side.  It went from the top of the transmission to a little metal fitting on one of the bell housing bolts.  It couldn't have gained more than 2 inches in height from the top of the transmission.  My old vent tube went all the way up to the top of the firewall.  I added a section of hose to the little metal fitting and clamped it down.  I looped the other end to an empty bottle just to see if I could get it to cough out any more fluid.  It was behaving now.  I clipped the hose just before the top of the firewall and capped it with an anti-siphon valve.

More AW-4 Tranny Swap



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