Specialty Transmissions

MM Sport/OD 5 Speed (Metric Mechanic Sport Overdrive 5 Speed)

1. Stating the Problem
Over the years, we have listened to customers describe what gear changes they'd like to see in BMW transmissions. Comments run like this:

• First gear feels like a "stump puller", it's too low.
• Second gear could be a little higher also.
• An overdrive 5th gear would be nice.
• But a close ratio 5 speed would be great too.

It's interesting to see people try to solve these problems. Take the 2002 owner. He installs an overdrive 5 speed behind his hot 2 liter engine, then he finds out that he doesn't have enough bottom end torque to pull 5th gear so he goes to a 3.90 or 4.11 rear end. He thinks this will make 5th gear more useful and give him a close ratio gearbox. Next, he discovers that 1st gear is so low that it feels like a "throw away" and he's close to being back to a 4 speed. Well, the Metric Mechanic Sport/OD gearbox is an end to this dilemma.

2. Solving the Problem
This special transmission has semi-close ratio gearing in the first four gears for optimal acceleration and a long legged overdrive 5th gear for cruising.

3. Advantages

• It's an "Ultimate Transmission"!
• It has a higher load rated support bearing that ties the main-shaft to the input shaft.
• Semi-sport gearing in the first four gears for improved acceleration.
• A longer legged overdrive (23% to 27% overdrive) for improved fuel economy, less engine wear and reduced driver fatigue.
• It works with the Metric Mechanic 5 Speed conversion kit, so it's easy to install.

4. Usage

• Street
• Driver Schools

5. Available In

• 245 & 240 Cases for 4 Cyl. BMW's
• 265 & 260 Cases for 6 Cyl. BMW's

6. Rear End Ratio (our recommended choice)

• 3.64, 3.90 & 4.11 for Metric Mechanic Sport/OD 245 & 240 transmissions (4 cylinder)
• 3.45, 3.64, 3.73 & 3.90 for Metric Mechanic Sport/OD 265 & 260 transmissions (6 cylinder)

Note: Small displacement motors need numerically higher gearing and larger displacement motors need numerically lower gearing.

Comparing the Metric Mechanic Sport/OD 5 Speed to BMW's Sport Close Ratio 5 Speed & the M5/M6

First gear becomes much more usable than the "stump pulling" 1st gear found on BMW 4&5 speeds. In fact, 1st gear (3.45-3.50) is fairly close to the 1st gear found in the close ratio5 speed. Second gear (1.90-2.00) falls in the middle between 2nd & 3rd gear on a close ration 5 speed. Third gear (1.26) is close to the same as 4th gear (1.24) in the close ratio 5 speed. Let's look at some of the advantages of the semi-close ratio 5 speed over the traditional BMW close ratio 5 speed. Actually, the first 4 gears are also similar to the M5 & M6 (3 piece) 280 gearbox.

City Driving
The close ratio 5 speed can grow rather tiring to shift because 1st gear is a dog leg back and to the left out of the conventional "H" pattern. So, 1st becomes rather annoying to shift into every time you come to a stop. Also, because most city driving is done under 50 mph, with a close ratio 5 speed, this means a lot of shifting in the first 4 gears as opposed to the first 3 gears in the semi-close ratio 5 speed. This type of transmission also has advantages over the conventional 4 or 5 speed in that 1st & 2nd gears are about 10% higher and this helps eliminate the "stump puller" feeling you get with stock transmissions.

Highway Driving
In this situation, the close ratio 5 speed turns your BMW into a buzz bomb - with the engine turning about 4000 rpm's in the 5th gear at 70 mph. With the Metric Mechanic semi-close ratio 5 speed the rpm's drop down to 3100 thanks to it's 23% overdrive 5th gear. Not only do things get quieter but there is less wear and tear on the engine and gas mileage goes up.

Mechanical Upgrades
These transmissions have been upgraded to "Ultimate Transmissions" so they have all the mechanical "goodies" our transmissions are famous for. In addition, they have a higher load rated support bearing that connects the main-shaft to the input shaft. This is done for two reasons:

1. To increase the torque rating of the transmission.
2. To prevent main-shaft deflection under load.

Note: This support bearing feature is unique to these gearboxes and our race boxes only.

In Closing
The Metric Mechanic Semi-Close Ratio 5 Speed is an excellent choice to couple up with our larger 4 cylinder engines using a 3.64 rear end. It will also work well with a warmed over 2 liter engine and a 3.90 or 4.11 rear end. Also, this gearbox is ideal for those wishing to install a 3.5 liter or bigger engine in an earlier 6 cylinder BMW using a 3.64 or 3.45 rear gear. With one of these motors, the 27% overdrive of 5th gear becomes quite easy to pull. M3 owners may want to consider this box for the sportier gearing through the first four gears and the unwinding feeling of a higher 5th gear. So, if you're thinking about a 5 speed conversion for an earlier BMW or you want to upgrade, instead of just rebuilding your present 5 speed, consider one of these special transmissions. In studying your gearbox options for the street, this transmission starts to look very appealing.