Installing Classic Motorsports Group’s
Deluxe TKO Overdrive Transmission Kit Into a 1967 Chevelle
by
Chuck Bonasera
Recently, Jeff Mortenson, one of the owners of Classic Motorsports Group, flew to the San Francisco Bay Area for the installation of a new Tremec GM TKO-600 5 speed overdrive transmission in a Chevelle Super Sport. I am Chuck Bonasera and the Chevelle is mine. The purpose of this collaboration is to document the TKO installation in the early series “A” body Chevrolet cars. Much has been published about the 68 through 72 Chevelles but this document is intended to fill the gap for owners of the earlier year models like mine. We hope it helps you out. This document is meant as a guideline only and, while accurate, implies no obligation or liability on the part of Chuck Bonasera or Classic Motorsports Group for the procedures contained herein. Proceed at your own risk.
We will start with the assumption that you know how to remove and install a transmission, although we will teach you an installation trick or two later. No modification to the Tremec transmission was necessary. It fit like a dream.
Extra Parts Needed:
You will need some extra parts and changes to a few things and I will go over that list so you will be ready. The GM TKO comes with both an electronic and mechanical speedometer pick ups. You will need to purchase either the electric speedometer kit or the mechanical speedometer cable kit for your application. Classic Motorsports Group has these kits available. A four page “tips” sheet was sent with my TKO kit and it covers this procedure as well as a ton of other items to know. The back up light switch is hooked up using a pigtail connector available from Classic Motorsports Group.
The TKO uses a 26 spline input shaft, rather than the stock GM 10 spline shaft. So I needed to replace my stock clutch disc. You will also need an offset shifter if you plan to use a stock console. The kit comes with everything else you need. Jeff thought of everything, including an allen head tranny bolt for the impossible to get to upper tranny mount.
Modifications:
As everyone has heard by now, the tunnel does need to be cut. It wasn’t a big deal, just time consuming. We had two people on the tranny and two on the tunnel. I’d allow a complete day for the modifications and the sheet metal covers but we were done by the end of the day. Jeff at Classic Motorsports Group has a template. We made my tunnel cut a little wider than some I have seen because of the narrow tunnel in the pre-68 series but the new sheet metal covers nicely and, other than a wider, flatter appearance, it fit well and didn’t add much to the height. The kicked out area to the left is the hump from the stock shifter location. We secured the front cover with pop rivets and made a separate cover for the rear, leaving room for removal of the shifter without removing the carpet again. The old Chevelle floor boot covers the hole but it’s close. Black RTV was used between the covers and the old floor pan to assure a watertight seal.
The rear tranny cross-member was usable as is except for a dent or two. We found inadequate clearance between the rear of the cross-member and a tang on the bottom of the TKO-600. We decided on heating and dimpling the cross-member to give more topside clearance rather than doing surgery on the tranny case. With the tranny bolted to the cross-member two of the frame holes lined up and two holes needed to be elongated, confirming other reports. No other modifications were required.
Installing the TKO:
We learned a simple trick that I hadn’t seen in all the years that I have been breaking cars. The hardest part of installing a tranny is alignment. Even with the tool, it’s a tough task. Many times in the past we have had to tighten the tranny mount bolts to “home” the transmission because the tranny, clutch Disc and pilot bearing NEVER line up. This time we got the TKO installed with the pilot shaft fully in to the clutch Disc but not into the pilot bearing. This is where most of the fight takes place. We previously attached and rough adjusted the clutch linkage and as one person pushed forward on the supported TKO, I slowly pushed the clutch in to release the pressure and the TKO went right into place. Make sure the pilot shaft is engaged into the clutch disc or the disc will drop and you will need to realign the clutch.
Back Up Switch:
The wiring for the back up switch is under the dash near the steering column or connected to a reverse/safety switch on the steering column. The two-wire plug is pink and light green. The pink lead has 12 Volts on it when the ignition switch is on and the light green wire goes to the back up lights. Using the reverse light connector that comes with the Classic Motorsports Group kit made this a simple job.
Shifter:
If you are not using a factory console simply use the Tremec top mounted shifter that comes with your transmission. If you are using a factory console you will need to purchase the low profile offset shifter. Because the offset shifter was not available at the time we installed the TKO, we tested a number of available offset shifters including the Tremec offset shifter. None performed as well as the low profile offset shifter from Classic Motorsports group. The shifter has a lower profile, a shorter throw and is much tighter through the gears. The internal design includes a custom spring washer set up that makes the shifter snap back to center. With a healthy layer of Dynamat or other matting installed on the top of the tunnel, the shifter boot is no more than 1/4 inch above the carpet. Be sure to completely cover the hole in the tunnel with matting to prevent engine heat from entering the car at freeway speeds. The shifter will fit underneath your console as well as locate your stick in the stock position within your console. My console did not need to be modified in any way. The shifter is available from Classic Motorsports Group.
Select Your Conversion Kit
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To achieve better sound deadening and heat control I installed the stock tar type mat, attached with 3M 777 adhesive. Then I installed a layer of Dynamat over the entire front area. Be sure that you console wiring is above the Dynamat for easy installation and that you cut a hole for the accelerator pedal to be attached. The stock floor boot will go over the carpet to keep road noise and little creatures out of the car.
Offset Shifter Installed
Final clean up:
| I reinstalled the carpet and had no problems. The console sits a little high in the front and may require some minor tweaking to get it to sit right but the end result is great. Note the cool Tremec logo and the 5 speed pattern on the shifter knob. OK, so you can’t see it, but it IS cool! Hook up the clock and get ready to head down the road. |
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Interior Installed |
Now just drive it:
As called for in the installation instructions, fill the TKO with just under three quarts of GM Syncromesh fluid from your Chevy dealer. Make sure you do the initial break in of the transmission as shown in the instructions. With the car on jack stands, start the engine and shift up and down through all the gears for about 10 to 15 minutes. You will start to feel the shifting get easier after a few minutes. The first road test found the TKO to be very tight, but it continued to loosen up during the drive. I did not build my car to race, it was built for crusin’. My reason for choosing the TKO-600 was the need for an overdrive for those long drives to events. I have 3.73:1 rear gears with a .64 overdrive. For me this is the perfect combination. 1st through 4th is aggressive, quick and the car has a great launch. With 50 series Radial TAs on the back, the 427 runs at 2000 RPM at 65 MPH. It is very drivable and takes off quickly. The new saying around here is "first, second, third and fourth gear belongs to me. Fifth gear belongs to my wife. I am amazed at how quiet the car is in 5th at 65 MPH. I couldn’t be happier.
THANKS JEFF!
By Chuck Bonasera, Dublin, Ca.
Team Chevelle Member
Nor-Cal Chevelle Camino