A couple of different cases are available for the Jerico four speed. Of primary interest are top as well as top and bottom loader cases. For ease of inspection and assembly, the top and bottom loader case (as shown in these photos) is preferred. It just makes access and service a whole bunch easier. Top loader (only) cases are often specified in road race applications. The reason is, a top and bottom loader case has an extra surface that might (a big might) leak.

How Difficult Are They?

The first thing someone (particularly someone with quarter mile experience) will say is "sticks are inconsistent." They’re hard to drive. I don’t think that’s totally correct. It’s the driver who is inconsistent and makes things hard to drive, not the transmission – particularly if the transmission is matched to the car. In fact, there is no real reason why a stick shift car can’t be any less consistent or harder to use than an automatic, particularly in a car that is properly set up.

Think about a typical high performance bracket race automatic combination (for example, a bracket race Powerglide). The ‘glide has two gears. First gear, in stock form, can be as high as 1.76:1 (1.82:1 first gear sets were used in OEM low HP applications). Aftermarket ratios are plentiful, more or less ranging from 1.68:1 to 2.18:1. Because of the rather high (low numerical) first gear ratios, a Powerglide really depends upon the torque converter. To get a ‘glide to effectively work in a drag race application, you’ll need an aftermarket converter. No big deal? Maybe it is. There’s more to this equation. In order to build horsepower, you’ll likely need a bigger cam – more lift, and more important, a bunch more duration. Add the big duration numbers, couple it with a car that likely weighs 3000-3500 (or more) pounds, stir in a relatively high first gear ratio, and in order to get the car moving, you’ll need to increase the stall speed of the converter (quite often by a dramatic margin). Therein lies the problem: The more stall speed you add to a converter, the harder it is to drive the car on the street (and hey, I’m talking from experience here – I once tried to street drive a big block-powered first generation Camaro with a Powerglide and a relatively tight 8-inch converter – it’s no fun).

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The perfect solution just very well may be a state-of-the-art manual gearbox in a street-strip car. First, let’s look at a Jerico gearbox. While Jerico is best known for their drag race gear boxes, they also manufacture a wide array of other transmissions. Many Nextel Cup cars regularly use Jerico four speeds, and believe it or not, Jerico also manufactures gearboxes for road race applications – even for Nextel Cup cars set up for road courses. Think about this for a minute: You have a car that likely tips the scales at 3700 pounds, has 700 or so horsepower under the hood and has to battle other similar cars around a road race circuit for hundreds of miles. The cars must be down-shifted and up-shifted constantly, with wide RPM ranges. The loads on the transmission are incredible. And they obviously live.

So why can’t you use some of this technology in a good-old-fashioned street strip car? You can, and it’s readily available (more on the pieces later). But what about something like a speedometer drive. They don’t use those in Nextel Cup cars. And few Bonneville cars use them either. That’s correct, but if you ask the folks at Jerico, they’ll gladly build you a transmission with a speedo-gear tailshaft. The third part of the puzzle is the clutch. Yes, high tech, low maintenance, low pedal pressure clutch assemblies are out there. You just have to find them (that’s another story). Let’s get back to the transmission:

Part of the puzzle, as mentioned above is getting a transmission built that allows you to shift easily in both directions – up and down. How Jerico accomplishes this is by way of a "road race slider". But let’s back up a minute and look at how these transmissions work:

One thing you have to consider is the synchronizers. The Jerico's uniquely designed gear, dog ring and slider eliminate weak, breakage-prone synchronizers. Shifting is handled by special "dog teeth" which project from the face of the slider and match "dog teeth" at the face of first gear or shift rings on the three upper gears. When a slider is moved toward a gear, the engagement teeth on its face mesh with the teeth on the gear's dog ring. This dog-ring engaging tooth design eliminates the harshness and rough shifting feel of a conventional transmission which has been heavily modified for racing (i.e.: a "pro shifted" gear box). As a matter of comparison, this special dog clutch configuration is very similar to a motorcycle transmission. If you've ever ridden a hi-performance bike (AKA "Crotch Rocket"), you know what the shift feel is like.

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Unlike the costly, one-piece cluster gears found on stock-type transmissions, the Jerico features easily and inexpensively replaced single components. Because of substantially larger engagement area, the wear of Jerico gears, dog rings and sliders is minimal. Road race and certain street applications incorporate a flat face with a three-degree undercut on the sides of the dogs, which provides for instant self-locking action. As the dogs of the slider and gear meet (as the shift begins) the wedging action actually pulls the slider toward the gear. The undercuts are the same on the acceleration and coast sides and both prevent the transmission from jumping out of gear.

It's no secret that stock street transmissions are designed for casual shifting. But when you lean on the shifter assembly, things can go bad -- quickly. And in many cases, it's not the fault of the actual shifter, the clutch set up or the driver. For example, Muncie (as well as Super T10) shift arms are designed to swing in an arc and the shift fork is free to pivot. As a result, the sleeve receives no real "guidance" from the fork. In contrast, the Jerico gearbox was configured from the onset for hard, full-force instant shifts. At each end of the case are three shift rails. The shift forks are rigidly mounted to these shift rails via socket head fasteners. The result is a completely guided fork that cannot move or twist on the sliders.

The Jerico shift arms are crafted from solid billet material. There is no welding present and unlike conventional transmissions, no weakening O-ring grooves. In order to seal the shift arms, lip seals are recessed in the shifter bosses on the side of the case. A pin located on the end of the shift arm engages a groove in the fork, moving it. The shift arms swing in an arc, but the fork, which is guided at both ends by the rail, travels in a straight line. Obviously, the shortest distance between two points is a straight line.

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There's more: Look at the typical rail motion in a manual gearbox: When shifting from First to Second, the shift rail motion is constant. The same applies to the shift from Third to Fourth. Unfortunately, this isn't so easy for the Second to Third shift. In this situation, the slider and fork must disengage Second gear, then come to a complete stop in neutral. Only then will the interlocks between shift rails allow the 3-4 shift rail to move. If the interlock in neutral is not included, the transmission will effectively jam between two gears. Jerico engineers solved the puzzle in a straightforward fashion. In order to speed up the shift, the 1-2 shift rail is fitted with two detents, designed to stop completely in neutral. This design prevents the heavy slider from overshooting and blocking out the 2-3 shift. When the shift rail is either in first or second, only one detent acts on it, so the shift feels light and smooth.

You should also consider gear ratios. A stock Detroit-built gearbox offers a couple of ratio choices -- wide or close. On the flip side is the Jerico. It's available with 300+ gear ratios -- enough for virtually any hot street strip combination.

It simply goes to show that a stick shift combination, when properly setup is likely a whole bunch quicker in a well-built street-strip than an equivalent Powerglide combination. And to be quite honest, if you drive a car with a high stall speed converter on the street for any length of time, it will get old in short order. The real point is, the stick shift car can be driven on the street with ease.

Jerico isn’t the only choice when it comes to high performance aftermarket stick shift transmissions. G-Force Racing Transmissions have an equally stellar track record, and like Jerico, they offer four and five speed manual gearboxes that are designed to live long and prosper in a high horsepower street-strip application. And yes, they too are very comfortable on the street, provided you pick the appropriate gearbox (FYI – you can order these transmissions with a speedo drive too).

A good example of streetable G-Force technology is the "GF-5R" transmission. It’s seen use in a wide array of applications. Some of these include: drag racing (both clutchless and clutch assisted), road racing, off road, and street/strip vehicles. It has also seen considerable use in conventional rear engine dragsters, roadsters, Bonneville salt flat racers and even in import drag racing. The layout of this transmission allows it to be used as a 4-speed if an overdrive is desired, or it can be set up as a regular 5-speed (5^th gear at 1:1). Like all G-Force Transmissions, this particular gearbox comes with your choice of a Long H-Pattern or Vertical Gate shifter. An air shifter can also be specified (but not likely for a street-driven vehicle).

Other available options for this model are a magnesium case (which saves 10 pounds), REM micropolished gears, needle bearing output (with includes a Mark Williams hardened yoke), and a torsion bar. What’s with the torsion bar? The torsion bar option is essentially what it sounds like. This is a long bar that runs through a hollow countershaft. This bar is connected to the input drive set at one end and to the rear of the counter shaft at the other end by way of splines. The idea behind the torsion bar is that the power transfers through this bar and consequently twists it slightly, but only for an instant. This power is then transferred to the counter shaft itself (the outer tube), thus driving the vehicle forward. This twisting action helps relieve some of the impact that normally gets transferred directly to the gears. This option is most often used in heavy cars (typically 3,000 lb. or more) or in applications with a very "stiff" clutch.

A number of different input shaft combinations are available. One of the most common is this: a 1-1/8-26-spline Chevy arrangement. At the rear, you can specify a 30 or 32 spline output (32 is a typically large GM TH400). Shifter choice is varied as well. This combination uses a conventional Long "H" pattern shifter. Vertical Gate shifters are also available along with air shifters for drag strip use only. Note too the speedo gear portal – it’s covered with tape in this photo.

G-Force transmissions (GF-5R included) are designed with a face tooth engagement system to ensure reliable shifting at speeds exceeding 14,000 RPM. All gears are manufactured from military grade 9310 high nickel alloy steel. The gears are also designed extra wide for more tooth contact, and excessive weight is removed for decreased inertia. A crowned profile is ground onto each gear after heat treating for more precise tolerances, then shot-peened which adds an extra level of strength.

Further to this, the GF-5R is based around a split-case configuration. In other words, you can split the transmission in half to service it. And by the way, the G-Force manuals are probably the easiest manual transmission in the world to service. Bearing supports are strategically located near each gear for the utmost stiffness, and low-friction roller bearings are incorporated in all gears and main shafts for near friction-free operation. All G-force transmissions use a Rail Fork design for smooth, effortless shifting with little wear as well as interchangeable gears that can be easily and quickly replaced.