Tunnel modifications for 5-speed conversion

I've installed a 5-speed conversion in my BJ7.  The Toyota 5-speed is a much smaller package than the Austin Healey transmission in general, and a bunch smaller than the center shift 4-speed with overdrive combination.  This smaller packaging provides the opportunity to pick up a bit more space inside the Healey cabin.

I've seen a number of approaches to the final tunnel fitment of the Smitty's 5-speed conversion (now "Healey 5-speed" transmission conversion by Pete Delany).  The approach is sometimes determined by which car you have...either the roadster style with its side shift tunnel, or the later center shift transmission.  The beauty of the center shift transmission tunnel used from the late MKII forward, is that it matches the Toyota shifter exit point.  That is assuming you have elected to go with the rear most shifter exit point, which is most generally used in this conversion.  The other nice thing about this tunnel is that it is fiberglass and makes for an easily modified do-it-yourself project.  If you have a 5-speed conversion in a side shift roadster, you could pick up one of these center shift tunnels to finish off your conversion.  Since I have a BJ7, I already had one of these center shift fiberglass tunnels, so I couldn't pass up the opportunity to custom fit it to the 5-speed conversion. 

Before I begin describing my approach to the project, let's take a look at the original transmission in place and the new 5-speed transmission in place.  (Pic #1, #2)  You can see the obvious difference in size if you look at the bellhousing comparison.

My goal in recontouring my fiberglass center shift console was to retain the original shape but to gain extra space.  At some point in the process, I also decided that I wanted to give my shifter pedestal a more finished appearance....maybe a bit more Aston Martin than Austin Healey (is it so wrong to say that??)  At any rate, with those goals in mind, I cut the top off the tunnel with my trusty high speed cutter and placed the tunnel back in the car.  I found that I could easily reduce the height by 2" and also slim down the rear sections to give the seats a bit more room.  I may have been able to lower the tunnel a bit more than that, but I didn't want to crowd the new transmission since I intended to ensure plenty of air flow around it....more on that later.  I pop-riveted aluminum strips in place to position the top section in its new location. (Pic #3)

  Then I layed some fiberglass mat to initially secure the top section and removed a few aluminum straps in the process. (Pic #4)  At this point I also cut some sections out at the rear to provide more clearance for the seats on both the passenger's and driver's sides.


 By the way, I did all the fiberglass work outside the car since it is messy to work with, although really not difficult.  With the tunnel back in the car, a careful examination revealed that the shifter pedestal wasn't as straight as I intended......and it was really much taller than was necessary with the new transmission.  Additionally, since I was planning on putting a more finished pedestal on the tunnel I wanted a bit more room to keep the overall height down.  So I cut off the shifter pedestal, repositioned it, and pop-riveted some aluminum straps in to hold it place. (Pic #5)  


Then I pulled it out and layed some more fiberglass mat.  The resulting shape and size were just what I wanted.  (Pic #6) 

With the initial recontouring complete, I set the tunnel on some saw horses and worked on the bottom.  My plan was to attach some aluminum heat shields that would direct the hot engine heat around the tunnel.  To do that I first mocked up some cardboard panels.  Once I was satisfied with them I duplicated the shape in aluminum panels.  I used 1/4" aluminum spacers to establish an air gap between the aluminum panels and the tunnel, then pop-riveted the panels into place. (Pic #7, #8)

Once satisfied with that, I did my final fiberglass mat work on the top side.  (Pic #9, #10)

With the tunnel back in the car, I began designing an improved shifter pedestal.  I intended to keep the rubber isolator boot that encirles the original Healey shift lever, designed to keep fumes out of the cabin, and add a leather shift boot above that to give it a more finished look.  I wanted the leather shift boot to be held down with a chrome bezel.  The other objective was to provide a means of getting the wiring down from the aluminum works rally shift knob without being seen.  (Works rally shift knobs have a switch for controlling the overdrive....but since I have a 5-speed, it controls the 7" driving lights.)  What I decided to do was to make a removeable secondary shifter pedestal to match the contours of the original....but that fits over the original.  This would provide a mounting surface for the chrome bezel and allow the wiring to be hidden.  I could also cover it in leather, similar to the original, to keep the original flavor yet providing a more finished look.  So with that plan I started.

The entire design would be centered around the chrome shifter bezel, so that is what I first needed to select.  After looking at a plethera of bezels, I settled on the one from the MGB.  Now, I know it doesn't have the genetic heritage of an Aston Martin, but it is tasteful, the right size, and easily attainable.  So that won the day.  I picked up a couple of used ones from my friends at Sports Car Craftsman (Link to SCC).  Paul Dierschow has a huge inventory of used parts.  I used one in my build stage and the other one was send to the rechromers in California.  I took the shifter bezel and fashioned a mounting plate out of 1/4" steel plate.  I taped the plate for the bezel mounting with 10/32 threads.  The plate is a little larger than the bezel to allow room to round the edge a bit and provide a nice fitting of the leather.....I thought it would look better with a softer curve at the top.  To that plate, I tack welded 4 straps (legs).  With that basic structure, I fit the plate over the shifter.  I bent and cut the legs to fit over the original shift pedestal.  (Pic #11, #12)  As you can see the tunnel has been covered with Second Skin (link to Second Skin) insulation in these pictures.

With the rough basic shape established, I cut some cardboard to fit around the frame.  I didn't try to do it in one piece.  I made 4 separate pieces to fit between each mounting strap.  I took this approach to make it easier to do the final fitting of the metal.  Once the general size of the pieces was determinded, I transferred the cardboard shapes to metal (I used 18 guage but other guages will work).  I took one at a time and welded a bit at the top, bent it, welded a bit more, bent it, welded a bit more, etc.,etc.. (Pic #13) 

  With this approach I was able to gently shape the metal to fit the bezel mounting plate and mounting legs. Then I took a coarse #80 grit rotary sander and did a bit of shaping.  (Pic #14, #15)  


I followed that with some body filler.....with the following results.  (Pic #16, #17)

The attractive chrome bezel is the center piece for the pedestal which will be leather covered and can be removed with 3 hidden screws.  The driving light switch wiring will run inside the leather boot and exit below the leather pedestal within the tunnel carpeting.....nothing showing. 

Steve Thomton

This project paper was first posted Nov. 29, 2009.