By Shad Ahlstrom
I used a very small flat blade screwdriver to rotate the torque converter through the bolt holes in the flexplate until the threads lined up. I twisted one bolt in there finger tight. I used a larger flat bladed screwdriver to rotate the flexplate tooth by tooth until I got all 4 bolts in finger tight. I torqued them down using the screwdriver to resist rotating the whole flexplate. The transmission cooler plumbing was a pretty close match between the XJ and the YJ. I had recently replaced the radiator and Radiator Barn was nice enough to add hose nipples to the bottom of the radiator for me. The output line had a quick connect fitting right near the passenger side fitting. I used the short quick connect end to go straight into the radiator. I had a B&M Supercooler to install so I didn't need any of that
quick connect stuff for the other end. I mounted the Supercooler in front of the AC condenser right behind the grill using the metal straps in the B&M kit. I plumbed the hose out of the radiator and into the bottom of the Supercooler. From the top of the Supercooler, I ran a hose to a barbed splice in the factory rubber hose. From there, it returns to the transmission. I needed to create a hanger from the oil pan to hold the lines tight.
I bolted the skid plate back on and bolted the trans mount to the skid plate. I cut the exhaust hanger off the pipe and installed it. I then took care of the rest of the wiring, minus the park/neutral switch and the reverse lights.
This TCU requires a reversed signal from the throttle position
sensor. What I mean is, the engine's TPS is a 5v system. At idle,
the engine's TPS sends out 0V and gradually sweeps up to +5V at full throttle.
This particular transmission control unit ('87-'90) has a reverse sweep.
+5V at idle and drops as the throttle is opened. I attempted to build a
voltage reverser with various resistors, condensers and a 555 timer but all I
could come up with was a logic circuit. +5 volts or 0 volts with no sweep.
I gave up after a few hours of playing with this. If anybody knows how to
do this properly, I'd love to know.
I bought a GM style TPS from the local auto parts store. It's from a
3.8L V6. I chose this one because it's cheap, adjustable and comes with an
arm as opposed to a socket.
I bent some steel to form a bracket that bolted to the throttle body and
added some ball chain to connect the two.
The sweep from the throttle linkage was a little greater than the sweep from the TPS so I needed to build a little bracket to prevent the ball chain from snapping at wide open throttle. After a little tweaking, I was able to get +5.1V at idle and +1.8V at wide open throttle. It's not 0V but it will do for now. I'll come up with a better system later on. I added about 1.5 quarts of transmission fluid to the transfer case and 6 more quarts to the transmission (8 total). Then I went back over every single bolt I touched to make sure I torqued everything. I set the TV cable by pressing in the button, twisting the throttle to wide open and releasing the button. This is supposed to set it automatically. I put the negative cable back on the battery and turned the ignition to ON. I looked over everything and it all seemed to be OK. No fuses blown, TCU is staying cool. Time to go for it! I turned the key to start. It cranked but no start. It's acting more like an XJ already...
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