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Shifty Business: Keisler TKO Five-Speed C3 Corvette Install

Project Shark Attack gets a new Keisler TKO five-Speed

Chris Petris Aug 4, 2006
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When we initially began Project Shark Attack, the car desperately needed an overdrive transmission of some sort. At the time, PSA was using the old school Borg-Warner T-10 four-speed, so a new tranny was a high priority. We initially wanted the O/D to slow the engine down and reduce some of the noises associated with the higher rpm of the original Borg-Warner. Engine and transmission heat is also lessened when the rotating pieces are slowed down, so when we chose the Keisler Engineering Tremec O/D five-speed, the choice was a win-win situation. At that time, the fuel costs were relatively cheap. It's hard to believe when we began the project, premium fuel could be found for $1.50-$1.75 a gallon, and we thought that was outrageous. With prices hovering around $3 a gallon, we're now ecstatic about the change to a more favorable tranny. higher gas prices are here to stay, and the Keisler Tremec PerfectFit five-speed O/D transmission makes the road trips easier on the wallet.

We contacted Keisler and gave them our engine and differential ratio specs and an idea of what we would be doing with PSA. They then assembled a complete package for us that had all the necessary pieces for the install including hardware. They suggested their TKO-500 kit that also included a new driveshaft ready to install. The only trip we had to make was to the local GM dealer to buy three quarts of GM Synchromesh transmission fluid. The supplied speedo cable for the Keisler Tremec is a hybrid GM-Ford unit, and it's nice to know that it's one less thing to locate, plus the correct speedo driven gear is calculated and supplied for you.

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1 We started by removing the driveshaft yoke straps. The crossmember-mounted shifter gets the ax and will that ever be appreciated. The only other bolts to remove were from the 51/48-inch hex-head transmission mount. When we look back at these photos, it's hard to believe the transformation. It was nasty underneath the car, and we cleaned for many days to avoid this mess during assembly.

The Tremec five-speed O/D has an integral back-up lamp switch in the transmission case so there is no linkage to be concerned with and no external switch next to the hot exhaust pipe like the original four-speed. For added safety, the five-speed transmission has an integral neutral safety switch that can be easily connected to the starter system. Another amenity is the integral Vehicle Speed Sensor (VSS), which can be used for an upgrade to fuel injection that requires a VSS or if you're installing an aftermarket cruise control.

If these points don't make a case for an upgrade to O/D, this little tidbit of info might do the trick. The Keisler PerfectFit five-speed requires no cutting of the floor or tunnel of your Corvette. The shifter is offset, allowing the shifter to be installed in the stock location with the stock shifter boot. Tunnel clearance is an issue at the top of the Tremec transmission, so the Keisler unit allows the install with adequate clearance.

The only issue for the installation is the bellhousing and transmission has to be installed as an assembly if the engine is in place. Actually, it's a loose fitting assembly. The bellhousing is placed on the transmission, then the transmission is put into position with the bellhousing bolted loosely so you have room to install the clutch pressure plate. Once we did the first install like this, we found the task was much easier than we anticipated.

We installed our Tremec as an engine/transmission assembly, which makes the install easier, but this procedure is not necessary. Once the install was completed, the benefits were immediately realized. The TKO-500 First gear ratio is lower (than the T-10), so the clutch life will be increased since there is no sliding of the clutch to get rolling. Once we were on the highway, shifting into that extra Fifth gear was a great improvement as the rpm dropped to 2,300 on the tachometer at 72 mph. We would have been cruising at 49 mph with the old T-10 and would have had to bring the rpm up to 3,250 at 72 mph.

Since the install, we are now cruising with the pack on the highways. Previously we would constantly watch the cars go by since we really didn't want to sustain the 3,500 rpm that would be necessary to keep up. As a matter of fact, with the Keisler PerfectFit Transmission and the Holley fuel injection installed in PSA, it's hard to go through a full tank of fuel before stopping for a reststop break. We should be able to go 200,000 miles on our fresh engine since we slowed the rpm down so dramatically. Like we said before, this was a killer win-win!

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8 Once the engine is in place, we can pickup the rear of the transmission and install the Keisler-supplied mount plate adapter. Keisler also supplies the transmission mount and new hardware for the complete mount install. The transmission goes up as high as possible to install the mounting plate.

Here are a couple of quick notes on bellhousing alignment concentricity. The auto service industry never worried much about checking alignment concentricity unless there was a problem with hard shifting, missed shifts, jumping out of gear, or vibration. We've found that most original equipment bellhousings were close enough to concentric to not worry about it. Today we have many choices of aftermarket engine blocks and bellhousings. This proliferation of so many parts increases the opportunity for less-than-satisfactory tolerances. This situation can lead to alignment problems (more than .005). If you want long transmission, clutch, and driveline life, check the bellhousing-to-engine concentricity everytime you mate these two driveline components together.

The latest development in bellhousing alignment is Lakewood's adjustable dowel pins. We wish these high-tech dowel pins were available when we assembled PSA. The Lakewood offset dowel pins allow you to rotate the pin to adjust concentricity, then run a set screw down to lock them in place. If you need to make a change, just loosen the set screw and rotate the offset in the dowel. Lakewood has three: PN15907 (.007 offset), PN15914 (.014 offset) and PN15921 (.021 offset). These pins make the task much easier, and once you've completed one, it's not too bad to do the concentricity adjustments. The extra work pays off in the long run.


12 Obviously, there is no floor to deal with, and we hope this gives you an idea how it all goes together. The shifter is bolted to the plate from above and since it's centered in the shifter opening, the task is simple. No sealer is required, but we usually use a 11/416-inch bead of silicone sealer around the outer circumference to keep the dirt and debris out.

13 The transmission "dog" that the shifter lever rests in has a cap that requires two screws to be installed. Hand tighten the retaining cap screws, and you're ready to check the shifting action, which is always a good idea before buttoning it all up. Once the shifter is run through the paces and everything feels right, install the cover and you're ready to go. Did you fill the transmission? Now is the time to do a double check of all fasteners from top to bottom.

14 Notice the shifter in the stock location with factory shift boot. We opted for the Hurst stick for PSA ,but they also have the original style with T-handle if you like. The immediate thing you'll notice is how tight the shifter is and how short the throw is. The best thing about the assembly is that the linkage is all internal. There are no shifter arms outside of the tranny case, with dirt and water getting things corroded and full of road debris. Job done.


Mr. Gasket
Midway Industries
Prescott, AR 86301



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