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AW-4 Transmission Swap

It was time to mount the coolers that I ordered from Summit Racing. 

Note:  As I write this page of the write-up, I can say that I drove the TJ home from Troy's shop earlier this afternoon.  It was about 55 degrees outside (welcome to your typical Arizona December day).  I drove about 15 miles in cross town traffic which equates to anything between sitting at a stop light and going 45 MPH.  The tranny temp gauge moved between 155 and 165 degrees after I was about half way through the trip.  It took the first half of the trip to get it up to 150 degrees.  I'll assume the thermal mass of the transmission itself took a while to warm up.  I was on the throttle a bit during the last mile and as I turned down the street to my house, I heard the 12V fan on the second cooler kick on.  It was not overly noisy but I did here it.  I pulled into the driveway and slipped the tranny into Park.  As I sat there, the fan cycled on for about 10~15 second and then would turn over for a minute or so.  This repeated itself for several minutes.  I put my hand under the fan to ensure it was sucking the air through the cooler and it was (meaning I had the polarity correct for the motor).  I was quite impressed with the volume of air it was blowing out of the cooler.  Likewise, I was very happy to see it cycling on and off.  This cooling setup is subject to change (do I have to say without notice?).  Summer is 6 months away and as configured, it may no provide enough cooling.  If something gets changed, it will most likely be the pre-cooler (without the fan) and it may end up getting moved so as to catch more air. 

OK...back to the installation.



Here is the pre-cooler as intended to go into the vehicle.  When I checked for space, I had ample room for the cooler but did not anticipate quite the amount of "overhead" required by the 1/2" NPT adapter and the 90 degree -6 AN fitting.  I tried to purchase a pair of 90 degree NPT to -6 AN fitting but the local performance shop did not have any in stock.  I took what they had (as seen in the photo above) and hoped for the best.

NOTE:  B&M recommends using anti-seize compound on the threads of their coolers.  I kind of "missed" that sentence in their cooler documentation and discovered that the threads in the cooler will gall very easily when an aluminum adapter is screwed into it. 

Well, I was wrong.  I had adequate clearance for one of the fittings but not for the 2nd one, due to a section of the floor in the TJ.  Troy didn't like the fit at all and so we discussed options. 


A quick trip down the street to a shop that builds drag racing engines provided the 90 degree fittings I originally had wanted but even those say higher than desired.  For what ever reason, B&M's 1/2" NPT threads were a little tight and most of the fitting didn't thread into the cooler all that far.  The decision was made to TIG weld the fittings into the cooler after a slight modifiction.  I cut 1/2 of the threads off of the cooler and likewise, 1/2 of the 1/2" NPT threads from the 90 degree fitting.  I removed enough of the aluminum threads (used a large sander) to allow the 90 degree fitting to sit down into the cooler's ports.  Troy likes to TIG aluminum and so he took care of that task. 

To get an idea of just how much space was saved, take a look at the blue -6 AN fitting in both photos and see where it lines up in relationship to the mounting brackets that are bolted to the cooler.  The overall height of the modified configuration is about 2" less that what I stated with.  Needless to say, there was plenty of mounting clearance now. 



Here is the pre-cooler, tucked up along the frame, driver's side, about the middle of the center skid plate.  I made the L shaped brackets for the cooler and Jessie welded them to the frame.  There is an air gap on the back side of the cooler (between it and the frame) of almost 2 inches.  I wish the cooler's orientation was a bit more broadside into the oncoming air flow but there isn't enough room there to make that happen.  In retrospect, I could have made one of the brackets a little shorter and angled the cooler rather than mounting it parallel to the frame.  This would have given a more frontal area to the air flow.  So....I'll see how it works out the way I have it.  As I mentioned before, this cooler may get moved to a new location in order to increase the efficiency once summer arrives.  Since you probably don't have Phoenix desert temps to content with when July/August rolls around, this may not even be a consideration for you.

I used the Parker hose to connect the inlet of the pre-cooler to the outlet of the AW4.  In case you were wondering, the AW4 outlet fluid port is the one furthest forward on the tranny (closest to the engine).  The Russell Twist-Lok AN fitting  is pushed into the Parker hose.  No hose clamp is needed (nor desired) in order to obtain the rated working pressure of 250 PSI. 


The 12V fan cooler was mounted at the rear of the vehicle, driver's side, adjacent to the upper spring perch and just forward of the gas tank.  I tucked it back into the corner as far as I could get it.  I had already check for axle up travel on the previous week's trail ride and so I knew just how far up the axle would travel.  According to my measurements I had about an inch to spare.  Let's hope I was correct.  I'll spend some cautious time on the RTI ramp just to make sure prior to hitting the trail. 


There are four mounting tabs on this cooler and I bolted it through the TJ's rear floor area.   Did I mention that I ended up using the straight AN fittings (that I bought for this cooler) on the pre-cooler?  No problem....I had ample hose to allow for the 90 degree AN fittings used here.  OK...so where did that red bling cover go on the left hand fitting?  I used it on another one that didn't come with one (different brand of fitting).  On the Twist-Lok fittings, the red cover is just that, a cover.  It serves no purpose other than to look pretty, which it seems to do when you compare the two fittings in the above photo.

This cooler has a built in thermostat, as I mentioned earlier in the write-up.  The documentation that came with the cooler provides a very easy to follow wiring diagram.  No power relays are needed and the built in thermostat controls power to the fan once you connect the electrical leads together.  Although I have not done it yet (it was not required to get the TJ rolling down the highway), it is my intensions to wire in a 12V LED indicator adjacent to the AW4 temp gauge so that I know when the 12V fan is running.  While I can hear it driving down the street in front of my house, I won't hear it on the freeway.  In case you want to wire one, just attach the indicators positive lead to the positive lead of the fan.  When the fan turns on (ie., gets +12V from the thermostat), the light will turn on.  Then....if the tranny temp gauge does not start dropping here is a problem.


More AW-4 Tranny Swap



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