Installing Classic Motorsports Group’s
Deluxe TKO Overdrive Transmission Kit into a 1967 GTO
By
Alex Goodsey

The following information describes the installation of a Classic Motorsports Group, Tremec TKO transmission kit into my 1967 GTO. The guys from CC5S are great to work with and they really put together a quality kit. I could tell by talking with them several times before buying my kit that these guys actually have done several install themselves so they know what they are talking about. That Classic Motorsports Group kit includes all the parts you need to get the job done correctly.

The first thing I did was build this beast to go in front of it. It's a 461 with 310 cfm KRE D-port heads and a Jeff Kauffman spec COMP hydraulic roller. Man it sounded wicked with open headers!

New motor waiting to be installed

As you can see the TKO is quite a bit bigger than the Muncie. It is about 3 to 4 inches longer and it has a lot more beef up on top of the tranny, especially in the back by the shifter.

TKO vs. Muncie – the TKO is noticeably larger

I decided to go with the McLeod offset shifter, instead of the stock Tremec shifter, in case I decide to use a console in the future. The McLeod shifter positions the shifter stub in the stock location when using a stock center console. If you are not going to use a center console, for optimal positioning, I would recommend mounting the shifter in the rear most position on the transmission.

McLeod 2” offset shifter installed  

I installed a new flywheel, pressure plate and 26 spline clutch Disc. I am still in the process of putting the recommended 500 stop and go miles on this thing to break it in before I really apply the horsepower. The tranny also recommends the same break-in period. It's killing me!

After I attached the TKO to the motor, I had to cut the hole in the floorboard. I had already chopped up the side of my transmission tunnel for a Hurst shifter several years ago so I removed the existing piece of sheet metal that I had fabricated for the Hurst shifter and then I positioned the template in place and drew an outline. I placed the template in the center of the tunnel and slid it all the way forward to where the tunnel makes the break up to form the firewall. I needed to cut about another 4”-5” behind the template to completely clear everything.

Tunnel template in place and tunnel cut

Once the hole was cut I put the motor and transmission into the car. WHOOOOHOOOO! I slid the factory crossmember in place to hold up the tailshaft and I secured the motor mounts in place. The transmission stuck up quite a bit through the tunnel. After a little more trimming of the tunnel and massaging the sides of the remaining tunnel to "aim" them straight up and over the transmission, I could see how it would all take shape.

Tunnel cutting

At this point I took the measurements for the new driveshaft so I could call them into Classic Chevy and get the custom driveshaft started. Next I began fabricating the new transmission tunnel patch. I used the tunnel patch from Classic Motorsports Group, it gives you plenty of extra material to deviate from the template if necessary.

Classic Motorsports Group tunnel patch for 64-72 Chevelle/GTO’s

Test fitting tunnel patch – the patch comes without the shifter hole drilled

Select Your Conversion Kit HERE

Since my transmission tunnel was so butchered from the previous Hurst shifter install, I had to improvise a little more. If you were starting with an automatic car floorboard, I would say this patch would have all the necessary metal needed. I decided to get some more 20 gauge sheet metal and go all the way over the previous hole so I would have less pieces.

Applying my personal touches to the tunnel patch

After the tunnel was completed, I called in the measurements for my new driveshaft. It arrived only four or five days from the time I placed my initail call to Classic Motorsports Group - that was fast! I decided that I should go with the larger 1350 u-joints for the extra strength since my engine is pushing 550-600 hp and over 600 ft-lbs. We used a combination ujoint in the back that connected the 1350 ujoint on the driveshaft to the1310 style, stock pinion yoke on my 12 bolt Chevy rear end. I ordered my driveshaft 1/2" shorter than the optimum measurement to make up for the longer 1350 style pinion yoke that I am planning to install later.

New driveshaft built by Inland Empire Driveline – it was part of the CC5S kit

The driveshaft fit perfectly, as did the CC5S supplied speedometer cable with the correct driven gear for my rear gears and tire size. Next, I re-installed my stock crossmember. The mounting holes in my frame rails lined up with an existing set of holes in the frame. All I needed to do to complete the crossmember installation was to drill a pair of holes to match up with the two rear crossmember mounting holes and I was good to go (in the picture below, you can see the original frame rail holes as well as where the crossmember mounts now). The center mounting position moved rearward about 1 ¾” to line up with the TKO’s mounting pad which is 1 ¾” farther back than the stock Muncie. I drilled a new hole in the crossmember for my emergency brake cable hanger and hooked it back up. I didn't even knock it out of adjustment.

Stock crossmember mounted to frame rail 1 3/4” rearward from stock location   

Stock crossmember mounted to transmission mount

Here is the finished product. I completed the welding of the floor and coated it with a good rustproof paint. I still have to get new carpet because the new hole is in a different place, and because the tunnel is actually bigger now, the carpet pulled away from the door sill plates about an inch on each side. New carpet is needed anyway.

 
Interior installed  

Complete and ready to drive