May 24, 2011

If you’ve spent any time at all hanging around the various online forums, you’ve seen the obligatory, Which manual transmission should I use? post. Most often, the poster wants a street/strip setup; something that will be easy to drive on the street but yet could withstand a few launches at the local dragstrip. We all want that, right? We all want something between the T-5 that’s in Dad’s ’93 Mustang GT and the Jerico that we see on YouTube getting the absolute snot beat out of it at the dragstrip.

The choice isn’t always so simple and that’s what we’re going to discuss in this article. Just like a camshaft or an intake manifold, there are a myriad of choices and they all hinge on several very key facets of your particular build. We’re going to break down the most common scenarios (street, street/strip) for you and then list the most common options under that scenario. You’ll notice that as we get toward the racier applications, the options will get fewer and more specialized. As an aside, we’ll only be including commonly available aftermarket transmissions. Otherwise, you’d still be reading this article next month.

Street/Cruiser

The first category, and probably most common, would be the street/cruiser category. This would encapsulate the daily drivers, and the guy with the super-sweet, restored ’67 Mustang fastback that never gets above 55 mph or 2,500 rpm.

For cars with engines under 350 hp/350 lb-ft, you pretty much have everything open to you as an option. This would include the Tremec T-5, the Tremec TKO 500/600, the Richmond 5/6-speed, the Tremec Magnum T-56, and for you old-schoolers, the Ford Top Loader. We know you’re saying, You said you’d only include aftermarket transmissions. Why are you mentioning the Top Loader? Well, there are many aftermarket Top Loader venders out there, offering everything from spice to nice, and we’ll talk more about that a little later.

For you guys with more horsepower, you can check yourselves against the comments that we will add beside each transmission in the notes below. For the most part, you want a drivetrain that will be able to withstand what your engine will put out. Since we’re talking about street cars only, we’ll assume that no one with drag radials or slicks will be in this category.

Tremec T-5

The T-5 has been around for a long time, offering reliable performance in various vehicles such as the Ford Mustang, Chevrolet Camaro, Pontiac Firebird, Chevrolet S-10, and more. Earlier versions were rated for less than 310 lb-ft of torque, while the new T-5 that you can get from Tremec is rated at around 330 lb-ft. While there are aftermarket gearsets available, the most common gear ratios for the T-5 include a 2.95:1 First gear and a 0.63:1 Overdrive. The input shaft is 1116x10-spline.

Pros:

    1. Very light at 75 pounds
    2. Great shifting transmission, quick and smooth
    3. Large variety of aftermarket shifters available
    4. Pretty cheap for a new gearbox
    5. Comes with its own factory shifter

Cons:

    1. Only rated for 330 lb-ft. We’ve seen stock 5.0L Mustangs break them

Tremec TKO 500/600

The TKO 500/600 is an absolute workhorse when it comes to passenger-car transmissions. The 500 and 600 denote how much torque the transmissions will hold. The key here is that it’s rated in continuous torque, so the TKO 500 can handle 500 lb-ft all day long. These transmissions replace the older Tremec 3550 and 3550-TKO transmissions that looked pretty similar, but didn’t have the torque ratings that these transmissions have.

The TKO 500 is available with two different input shaft choices: 1116x10-spline and 118x26-spline. The latter increases the torque capacity of the transmission, but Tremec doesn’t list a separate torque rating for that option. For gear ratios, First gear is a 3.27:1 and Overdrive is a 0.68:1.

The TKO 600 is available only with a 118x26-spline input shaft. It is, however, available with two different Overdrive ratios, 0.82:1 or 0.64:1.

Pros:

    1. Medium weight at 105 pounds
    2. Large variety of aftermarket shifters/handles available
    3. Will handle a large amount of horsepower/torque
    4. Many different shifter positions available (up to eight), so you can put the shifter where you need it
    5. Short input shafts available so that you can use a TKO with an older Top Loader bellhousing
    6. Comes with its own factory shifter. It also has a mechanical speedometer provision, along with an electronic speedometer provision

Cons:

    1. Doesn’t like to be shifted quickly at higher rpm due to manufacturing tolerances and design
    2. Larger than a Top Loader or T-5, so transplanting this into your older muscle car may necessitate some modifications. For instance, to achieve the proper pinion angle in an older Mustang, the bracing inside the transmission tunnel may need trimming or a little persuasion. On some older Galaxies, the transmission tunnel has to be completely rebuilt