GM's horseshoe-style automatic transmission floor shifter looks great sitting in '68-'72 Chevelles, '68-'72 Camaros, '70-'72 Monte Carlos, and '68-'69 Impalas. But in stock form, the horseshoe shifter (sometimes referred to as the staple style shifter) is far from the ultimate setup for high-performance driving. An ambitious driver wanting to manually shift with this lever quickly learns that the lack of a positive stop for each gear results in missed shifts or unwanted Neutral engagement. As odd as it may seem, some Chevy owners are content to live with the less-than-competent OE shifter. Others, however, toss it for an aftermarket unit.
The sloppiness of the factory shifter in Bob Thomson's 1969 Chevrolet Chevelle SS396 drove him to seek a better way to manually shift his Turbo 400 while maintaining the interior's stock appearance. The factory horseshoe shifter incorporates a pawl bar that rides along a detent plate. This plate determines how the shifter moves from gear to gear. Bob applied some careful and creative thinking to come up with a redesigned detent plate with ratchet-shifting ability. He tested the design in real-world driving, perfected the detent plate, and formed Thomson Performance to supply the part to fellow enthusiasts. This ratchet-shift detent plate can be easily installed within a couple of hours and is available for less than $100 through Shiftworks. Applications for the horseshoe shifter upgrade include Turbo 350, Turbo 400, and TH700-R4/TH200-R4 Overdrive transmissions.
With the new detent plate in place, the three-speed automatic driver starts out in First gear and squeezes the shifter button up to make the 1-2 shift. The 2-3 shift is a simple matter of slapping the shifter forward to Drive, employing a positive stop that does not allow an unwanted shift to Neutral. Bob has been driving his Chevelle with his detent plate for more than two years, and the functionality—not to mention the fun factor—is incredible. Positive shifts for street driving and occasional all-out blasts down the quarter-mile are now a reality.
1 The first step in swapping the horseshoe shifter detent plate is to remove the console, which comes apart in three pieces. A Phillips screwdriver is used to remove the gear indicator plate.
2 With the screws removed, the gear indicator plate lifts out of the way.
3 The console top plate is also removed to gain access to the console fasteners.
4 The console is held in place with a combination of 3/8 and 7/16 fasteners. Make sure you have removed all of them before attempting to remove the console.
5 The '68-'72 factory horseshoe shifters used a universal detent plate in both the two- and three-speed transmissions. Our subject car has the three-speed Turbo 400. Make sure the emergency brake is engaged and wheel chocks are placed behind the tires to prevent rolling. Put the shifter in Drive and remove the OE detent plate's forward-facing fastener.
6 If the shifter is factory stock, the rear of the detent plate will be held in by a rivet. Removing the rivet is best accomplished with a Dremel tool. Carefully cut an "X” in the rivet head, and then drive it off with a screwdriver or small chisel. The angle is not the best, but be patient as the rivet is ground out.
7 Once the OE detent plate is gone, the Thomson Performance Ratchet Shift detent plate can be installed. The fastener holes are threaded for ease of installation.
8 The fasteners are provided by Shiftworks. Install the new front fastener, but don't tighten.
9 Install the rear fastener in the detent plate, but again, do not tighten.
10 With the shifter in the Drive position, adjust the Thomson Performance detent plate so the pawl bar is fully engaged in the Drive detent. Pawl bar engagement is adjusted by raising or lowering the detent plate. When properly adjusted, tighten both detent plate fasteners.
11 It is critical that the shifter cable be properly adjusted. The distance from the forward face of the shifter bracket to the center of the cable pin at the handle should be 6¼ inches.
12 With the shifter properly adjusted, jack up the car and support it with jackstands under the framerails. Note that Bob Thomson stays to the side of the car as he sets the jackstands in place. When the jackstands are positioned, lower the jack, and make sure the car is secure by pushing the car from side to side. Never go under a car that is supported only by a jack.
13 Locate the shifter cable and attachment bracket. Spend a quiet moment in a fit of jealousy over Bob's immaculate undercarriage.
14 The distance from the rearward face of the attachment bracket to the center of the cable attachment pin must be 5½ inches for the Turbo 350 and Turbo 400 transmissions.
15 Reinstall the console, and your totally stock-appearing horseshoe shifter is ready for some gear-slappin' fun.
16 Take the car for a testdrive to make sure the shifter is functioning properly. Get out and drive your muscle car, promote the hobby, and smack that Thomson Performance horseshoe shifter. MCR
