There's nothing like the sound and exhilaration of winding that motor up in your hot rod, reaching down, stirring the gears, and having all that horsepower throw you back into the seat as the car lunges full steam ahead. It's something that just can't be replicated with an automatic. Sure, there are shift kits and manual valvebody conversions and things like that but it's just not the same. Try sidestepping the clutch with a 700-R4-it doesn't happen.
But there are numerous advantages of running a manual transmission over an automatic as well. For one, automatic transmissions tend to be physically larger. The bodies of most automatics need to be large enough in the mid section to house the valvebody and all the clutches and bands associated with the internals of a slush box. This can oftentimes be some valuable real estate in the relatively tight confines of most street rods. Manual transmissions are usually narrower from the bellhousing back due to the fact that the transmission body need only be large enough for the gears, shift forks, etc., inside the body of the trans. Automatic transmissions also tend to generate more heat, and therefore need to be cooled by external means. This usually equates to either running a transmission cooler incorporated into the radiator (which can inhibit the radiator's ability to effectively cool the engine coolant), or running a separate tranny cooler (which takes up even more space). Additional drawbacks to running an automatic transmission are that most need a kick-down cable of some sort attached to the carburetor or throttle body, a vacuum line connected to the intake manifold, a dipstick, and of course, the shift linkage. In a tightly packed car such as a '29 Ford roadster, all these small items can quickly add up.
These were a few of the points taken into consideration when the time came to choose how to shift the gears in my '29 roadster project. I wasn't subject to the availability of a transmission or an adapter because I will be using a small-block Chevy engine. I was, however, limited by space and strength. The confines of the chassis and the roadster body are not very accommodating to the larger-sized transmissions, and the engine is going to be putting out somewhere in the area of 500 hp, so whatever ends up going behind it-transmission, driveshaft, and the rearend-needs to be able to handle the abuse.
When it comes to available, modern manual transmissions, my first choice was the obvious junkyard go-to: the venerable T5. They came in a variety of makes and models, from trucks to passenger cars for years. In fact, the T5 is the only American-made standard transmission to span more than 20 years of production. They also share a number of similarities throughout the years and applications. One common swap was to use the tailshaft of the weaker Chevy S-10 T5 and install it on the stronger Camaro and Mustang counterpart, moving the shifter location forward approximately 7 inches. While their availability and their many interchangeable parts make them ideal for use in the street rodding industry, the fact is the strongest production T5-the World Class models that first appeared in Ford Mustangs in the mid-'80s-are only capable of handling around 300hp. That's 200 ponies short of the expected output of the engine, and to avoid worrying about when that little silver fuse between the engine and the rearend's gonna blow, I opted to go with something that could handle the power and abuse I plan on dishing out on it.
That led me to the modern-day big brother to the T5, the Tremec TKO. The Tremec TKO-available as either the TKO-500, rated at 500 lb-ft of torque, or the TKO-600, rated at 600 lb-ft of torque-is the premiere high-performance overdrive five-speed manual transmission. Originally designed by Transmission Technologies Corporation as a replacement for the earlier TR-3550, the TKO has been significantly upgraded, making it more robust, flexible, and versatile. The higher center distance from main shaft to countershaft allows for larger gear sizes and higher torque carrying capacity, and the internal three-rail shift system with cast-iron shift forks equal a very robust transmission design. Eight available shifter locations, dual electronic and mechanical speedometer pick-ups, multiple crossmember mounting configurations, and three different available input shafts make the TKO one of the most versatile transmissions available. Three different overdrive gear ratios are also available. A .64 or .68 ratio reduces engine rpm and increases fuel efficiency, while the .82 ratio is ideal for long straightaways for high-performance racing.