auto mechanic

Big Red has gone through a few transmissions over the years. When Big Red was first built by Bill Osborne in 1988, it was equipped with a Jerico four-speed. That transmission was adequate for Road Racing for many years. Big Red is not a lightweight race car; it tips the scales at 3,300 pounds. Now factor in horsepower, tire size, and tire compounds, all of which have improved or increased over the years. What previously worked might not continue to work. In 2016, Big Red received a new G-Force GSR four-speed manual racing transmission. According to G-Force, “The GSR is absolutely the end of the line in terms of absolute strength and performance from a four-speed racing transmission.” Only time will tell how it holds up to the punishment dished out by RJ and Big Red.

Written in Sharpie ® on the transmission (and the tag) are all the specs. The gears are: 2.26 (first gear), 1.58 (second gear), 1.19 (third gear), and 1:1 direct drive (fourth gear). With the correct rearend gear, these are great for Pikes Peak. Also written are the numbers 21/23, stating that the input drive has 21 teeth and the cluster drive has 23.

The GSR was bolted to a bare block and a Tilton bellhousing for mock up in the chassis. The transmission crossmember was narrower in 1988. During the rebuild, they widened the transmission tunnel, so the new manual transmission crossmember also is wider. The crossmember mounts to tabs that protrude through the floorpan up into the chassis structure inside the cockpit. Keeping the structure above the floorpan left more clearance under the car.

The Long internal-rail shifter is an amazing piece, and has a unique design for a four-speed that mounts directly over the center of the transmission, in line with the output shaft. The slim design allowed Dave to build a narrower (compared to the Jerico) and shorter transmission tunnel. The design gives more clearance between the shifter and the driver’s seat. Larry inspects the GSR before it’s mounted to The Beast for installation in the chassis. The input-shaft bearing is much better quality than the one from the previous transmission. The GSR should be a better match for Big Red’s power and versatility. Dave chose to use a Tilton 7.25-inch clutch to reduced flywheel weight, and its small diameter gives the bellhousing considerable ground clearance when installed in Big Red’s chassis. The GSR still has plenty of ground clearance behind the 7 3/4-inch-deep dry-sump Olson Motorsports pan, which is same depth as a stock wet-sump pan.

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