We ask a lot of our classic Camaros. After all, they were never designed support the parts we’re dying to transplant into them. Back in the ’60s, transmissions were small and, with only three or four gears, they didn’t need to be any bigger. Today, one of the most popular transmissions to transplant into early Camaros is the Tremec Magnum six-speed. The four “go” gears and two overdrives in the T56 Magnum offer the perfect blend of performance and highway manners. The big problem is that it’s far larger than what GM envisioned when they designed the Camaro’s transmission tunnel.
The simple solution is to do a little metal surgery and make the tunnel roomier. A task made simpler thanks to the transmission tunnel cap offered by Chris Alston’s Chassisworks. This preformed panel takes a ton of fabrication out of the equation and allows someone with basic tools and some welding skills to make their tunnel “Magnum friendly.” To preform the operation on our '68 Camaro project (Track Rat), we headed over to one of our favorite shops, Best of Show Coach Works in Escondido, California, to get Track Rat ready to receive its T56 Magnum.
01. To make sure we add enough room for the T56 Magnum in our '68 Camaro project, we installed it along with a composite LS engine we have at the shop. To support the transmission, we used the trans crossmember (PN 5916-F10-05, $256) that came with the Chris Alston’s Chassisworks front subframe. This also gave us a chance to see how our new stainless Hooker 1 7⁄8-inch first-gen LS headers would fit. They weren’t designed for this application, but they fit perfectly and cleared the subframe.
02. We were able to make the marks needed under the Camaro and start removing the top of the factory tunnel, making sure not to go bigger than the tunnel cap we sourced from Chassisworks. The T56 Magnum was supported by the Chassisworks tubular crossmember that’s designed to work with our subframe or with a stock subframe (using adapter plates).
03. Here is what we removed from the factory '68 Camaro tunnel. The new cap will raise the tunnel about 1.5 inches. Not a lot, but enough to clear the new T56 Magnum.
04. This is the transmission tunnel cap from Chassisworks (PN 5922-F10, $101). It came preformed and ready to rock complete with a mating flange on the downward edge. The cap extends from the firewall back to the seat crossmember.
05. We also marked where the shifter would poke through and made the necessary hole.
06. Best of Show Coach Works fabricator Kyle Phillips installed the new tunnel cap on the '68 Camaro and clamped it in place. As you can see, we needed to fabricate a panel to transition to the firewall. For easier panel fitment, Kyle used a marker to scribe a cut line in the top of the tunnel cap.
07. He then used a pair of snips to remove the marked section.
08. With that done, he drilled some holes around the perimeter and used Cleco fasteners to hold the new tunnel cap in place. Cleco fasteners and the required pliers are inexpensive and come in handy when doing all sorts of sheetmetal welding.
09. We then busted out our trusty Millermatic 140 MIG welder, which is a perfect size for sheetmetal work.
10. With the tunnel cap secured by five Clecos and a couple of locking pliers, Kyle started tacking it all together.
11. A tack every couple of inches was more than enough to do the job.
12. Next, it was time to fabricate the panel to tie the tunnel cap into the forward section of the trans tunnel. For this, Kyle had someone hold a piece of heavy-stock paper under the car so he could trace the opening with a marker.
13. After attacking the paper with some scissors, this was the end result.
14. If we made the panel the same size as the hole, we wouldn’t have any overlap to weld to. The solution was to trace the template onto some steel, then use 1⁄4-inch tape to add a flange edge to the panel.
15. The panel was then cut out with a pair of snips and curved to match the tunnel.
16. Kyle then used a pair of pliers to slightly bend the curved edge of the panel so that it would better mate up with the tunnel cap and the curved section he cut out earlier.
17. The front edge was tacked down and Kyle used a hammer to force the far edge down and tack it in place.
18. More tacks were added until the patch panel was as secure as the tunnel cap.
19. And just like that the T56 Magnum had more than enough room to fit under our ’68 Camaro.
20. The last steps were to give the panel a coat of black Wurth paint and apply a bead of Lord Fusor seam sealer. To get the best result, Kyle taped off the welded areas, applied the seam sealer, spread it with a disposable brush, then removed the tape.
21. Later, once we pull the mock-up LS engine and T56 Magnum trans, we will repeat the seam sealer part on the underside of the Camaro and then give it a coat of Wurth SKS stoneguard undercoating.
22. At the last moment, we received a sweet little trinket from Brian Finch over at Hot Rod Transformations. The nice part about this shift boot kit is that the lower ring is welded to the tunnel and the boot is secured to it. This is far better than poking through the carpet with self-tapping screws.