C3 Corvette Five-Speed Swap Kit From Silver Sport Transmission

For classic muscle car owners, three and four-speed transmissions just don’t cut it on today’s modern highways. In the case of a four-speed C3 Corvette, the low final gear of the factory box can result in buzzy cruising on the interstate.  YouTuber TacoJoe has a 1977 Corvette with the four-speed manual and he tells us his car is so frenzied on the freeway that he just plain avoids high-speed roads. That’s something a Corvette owner should never have to contend with.

To remedy this problem, he installed a Tremec TKO 600 five-speed gearbox, part of Silver Sport Transmission’s Tremec TKO PerfectFit Kit for the C3 Corvette, and takes us through the install process step-by-step with a very informative video. If you have a classic car that needs a taller final gear, you should get to know Silver Sport Transmissions. They are the gurus of adding more gears to your classic Corvette or muscle car.

Silver Sport Transmissions, a distributor of Tremec transmissions, is the industry leader in the research and development of gearbox kits to modernize the drivetrain of classic cars, trucks, and street rods. Their SST A41 Automatic, Tremec TKO and T5 5-Speeds, and Tremec Magnum 6-Speed PerfectFit and RestroFit Kits are the best fitting and most complete kits available on the market today.

Let’s Take a Look At The Transmission Swap Performed by TacoJoe.

Three elements make up the C3 Corvette PerfectFit Kit TacoJoe chose for his C3:

  1. Transmission modification to the shifter and the housing
  2. Custom brackets designed by SST
  3. Custom SST Driveshaft

The 1977 Corvette came from the factory with a Borg Warner ST10 four-speed and will be replaced with Tremec TKO 600 five-speed transmission. The fifth gear will provide a tall overdrive gear resulting in smooth, calm cruising with increased gas mileage. Both the old transmission and the new box have identical input shaft spline counts and the new five-speed is the same dimensions as the old unit and will marry with the bell housing with no problems.

Silver Sport modifies the TKO 600 by machining the tail shaft housing to make sure the transmission clears the cross member, and it will fit in the transmission tunnel when installed. The other mod is the relocation of the shifter placement, so it perfectly fits the shifter opening in the fiberglass floor pan of the old 1977 fiberglass dreamboat.

Installation

Although you can do this swap with the engine installed in the car, both Silver Sport and TacoJoe suggest pulling the motor to gain access and ease assembly. TacoJoe was going to rebuild and beef up the motor anyway so he went ahead and pulled it out of the car and will reinstall the new transmission and mill as one unit.

The kit comes with a pilot bearing and Silver Sport strongly recommends installing this as opposed to a bushing. The TKO 600 uses tapered bearings as opposed to ball bearings on the older unit. The pilot bearing is a better and stronger way to locate the input shaft.

TacoJoe installed a new flywheel and then establishes the most important spec of the build. Aligning the crankshaft centerline to the input shaft centerline at the bell housing. Any deviation here and you’re asking for problems down the road.

The two shafts were slightly out of whack but TacoJoe cleverly fabs up a fix and when he gets the situation straightened out, the two shafts are within tolerances suggested by Silver Sport. Next up, the bell house and attendant parts are assembled, and TacoJoe conducts some deft massaging and bolts the transmission up to the engine.

Reinstalling The Engine And Transmission Back In The Car

With the engine and transmission now one unit, it’s time to install it back in the Corvette. Using a two-ton engine hoist with a leveler, the motor and transmission slip back in, easy breezy. There was some concern about bumping up against the radiator core support but that proved easy to avoid and a crisis was averted.

Regarding the massaged transmission housing, it fits well in the Corvette and is a testament to Silver Sport and its superior engineering skills. The new transmission fits in the tunnel just right, the yolk isn’t too close to either side,  and the shifter was exactly in the right spot.

Moving forward, it was time to install the shifter and transmission mounting bracket. The new transmission is bigger than the old unit and although TacoJoe had a hunch he could have installed the gearbox with shifter attached to the tranny housing, he removed it just in case. The shifter fit well and he had no problem with the installation.

With that out of the way, the next step is bolting up the custom mounting bracket to secure the aft end of the transmission case to the frame. It bolts in easily with no modification. The kit comes with a custom exhaust bracket as well, but TacoJoe modified the factory one to his specifications.

Connecting the Driveshaft

With the motor and transmission located and bolted in place, now it’s time for the driveshaft installation. The process went smoothly except there was a deformed yolk seal at the end of the transmission.  Although this was cause for concern, the install progressed with the caveat of keeping an eye on that connection to monitor the situation for any leakage.

After all the heavy lifting is done, Silver Sport offers some very cool parts like a shifter and console plate that will add a touch of OEM look to the finished product.

This ease of TacoJoe’s install is a testament to Silver Sport Transmissions and the benefits of buying a well-engineered kit as opposed to chasing down all the parts you need from online catalogs and parts stores.

Although TacoJoe still has a bit of work to do to get this old C3 up and running, he assures us that it will be back on the road so stay tuned to his channel for all the updates on this 1977 Corvettes and test driving the completed car.

Article Sources

About the author

Dave Cruikshank

Dave Cruikshank is a lifelong car enthusiast and an Editor at Power Automedia. A zealous car geek since birth, he digs lead sleds, curvy fiberglass, kustoms and street rods. He currently owns a '95 Corvette, '76 Cadillac Seville, '99 LS1 Trans Am and big old Ford Van.
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