Metric Mechanic - Transmission Questions & Answers

1. What is the "Ultimate Transmission"?
2. Specifically, why is an "Ultimate Transmission" superior to a "new" or factory rebuilt gearbox?
3. Can all BMW gearboxes become "Ultimate Transmissions"?
4. What kind of lube do you recommend using in your transmissions?
5. Are there other gearing options available, like close ratio five speeds?
6. My shifter feels sloppy; What does this mean?
7. How can I tell if my transmission needs rebuilding?
8. How do you define a "rebuildable core"?
9. How do I determine if my core is rebuildable?
10. If my core isn't rebuildable?
11. Can I trade my rebuildable 4 speed for an "Ultimate Transmission" 5 speed?
12. Can I trade in my automatic on an "Ultimate Transmission", 4 or 5 speed?
13. Does Metric Mechanic do complete 5 speed conversions?
14. Can I trade in more than one core for an "Ultimate Transmission"?
15. If I decide to do the work myself, are there installation instructions?

1. What is the "Ultimate Transmission"?
It is the result of a rebuilding and redesigning procedure that eliminates the three shortcomings in all BMW manual transmissions:

1. Premature layshaft bearing failure.
2. Short synchronizer life span.
3. Weak clutching action of the synchronizer.

5. Are there other gearing options available, like close ratio five speeds?
Since the transmission gear ratios are the "torque multiplier" between the engine and differential, it's obvious to see that engine power can actually be enhanced by correct transmission gearing. Gear ratios are to transmissions what horsepower is to engines. Metric Mechanic is proud to offer 4 specialty transmissions with optional gear ratios for street and competition.

1. Metric Mechanic Semi - Close Ratio for Street
   This offers semi-sport gearing in the first 4 gears combined with a 23% overdrive 5th gear.
2. Metric Mechanic Close Ratio 4 Speed for Road Racing or Driver's Schools
   This transmission keeps a competition engine operating in it's power band.
3. Metric Mechanic 2 Speed for Circle Track
   A transmission designed for 1/2 mile or smaller tracks.
4. Metric Mechanic 4 Speed for Circle Track
   This transmission is designed for 1/4 mile to 5/8 mile tracks.

6. My shifter feels sloppy; What does this mean?
Part of what makes shifting a transmission pleasurable is a well defined shift pattern. The more side-to-side movement of the shifter, when in any gear, the more difficult it becomes to find the "gate" for each gear which impedes the effectiveness (not to mention the enjoyment) of brisk, clean gear changing. Although the "H" pattern is determined by the internal transmission design, it is the external shift linkage usually responsible for the "sloppiness" felt at the shift knob; specifically, two nylon bushings! The following parts form the shifting mechanism from the transmission to the hand:

1. Shift coupling
   Is "pinned" at one end to the transmission selector shaft and is clipped to the shift rod extension by means of a nylon bushing.
2. Shift Rod Extension
   A horizontal rod with two perpendicular projections that slip through the coupling bushing at one end and the lower shift lever at the other.
3. Lower Shift Lever
   Is the pivot ball for the whole shifter, the direct connection with the shift rod extension, via another nylon bushing, and the internal support for the upper shifter and knob.
4. Upper Shift Lever
   Circlips to the lower shift lever by sliding over two closely fitting rubber bushings that, when assembled, give the impression that the shift lever is one solid piece.

Conclusion
The nylon bushings, in the coupling and the lower shift lever, have always been and still are the weak points in the shift mechanism. And furthermore, the only things available from the factory are replacement couplings and lower shift levers with nylon bushings until now! Metric Mechanic has developed a bronze bushing short shift kit that makes sloppy shifting obsolete.

7. How can I tell if my transmission needs rebuilding?
Bearing Noise
With the car idling in neutral, repeatedly depress and release the clutch pedal. Listen for a significant increase in the noise level of the transmission when the pedal is "out" and for the noise to go away when the pedal is "in". This could best be described as a low pitched rumbling or "static" sound. All transmissions make some noise. That's why there are numerous points of contact with the gearbox and the shift linkage where sound and vibration absorbing materials are used. In addition, body insulation, engine noise and road noise help to keep normal operating noises at bay. Excessive noise would be so loud as to compete with the engine noise, or prevent normal conversation in the passenger compartment.

Synchro Weakness
Contrary to popular belief, a transmission that works correctly can be shifted into any gear, up or down, without grinding, as quickly as the shift can be executed (providing the clutch is used). Some folks would consider this to be abusing the transmission and that grinding when shifting is not the fault of the gearbox but the driver's inability to execute a smooth shift. This statement can be interpreted in two very different ways. If done correctly, and "new" or newly rebuilt transmission will up-shift or downshift into any gear without pausing between gears. If it is constantly shifted aggressively and frequently, in 10,000 or 20,000 miles the driver will experience his or her first "grind", usually while downshifting into second gear. At this point, the driver has two choices, stop downshifting or pause slightly before engaging the desired gear. If the driver opts to refrain from downshifting, the synchro won't get any worse but neither will it improve. Whereas if downshifting continues, "pauses" will become "hesitations", "hesitations" will turn into "waiting" and over time "waiting" will have to become "double clutching". This progression is very gradual, over the span of many thousands of miles. Often the driver doesn't even realize that the car has taken over and is teaching him to coax the transmission into gear. Now, is the "art of shifting smoothly" discovery of how to make the mechanism operate in it's most efficient manner or is it a collection of continually slowing motions that are directly related to ever weakening synchronizers? This all boils down to the following: BMW has continued to couple a strong and responsive engine to a dependable differential through a "weak-link" gearbox. The really sad part about all of this is that we have progressed from toleration to expectation and finally placed blame on the driver's inabilities! The "Ultimate Transmission" is the only unit that allows the driver alone to decide how he or she wants to shift, rather than allowing the gearbox to dictate how the driver has to shift.

8. How do you define a "rebuildable core"?
A rebuildable core is one that has no damage to the drive teeth of any gear or the layshaft, meaning, no pitted, disfigured or missing teeth. Irreparable core damage is usually due to:

• Rear layshft bearing disintegration
• Rust
• Digestion of metal fragments
• Lack of lubricant

External case damage, loose or broken drive flanges, shift mechanism damage or the like will not prevent a core from being rebuilt.

9. How do I determine if my core is rebuildable?

In a 4 cylinder, 4 speed:

1. First remove the drain plug and carefully examine the cluster of gear teeth closes to the hole. Inspect each tooth for any pitting (holes on the surface), rust, deformation, chips or parts of teeth missing.
2. Next, remove the fill plug and look for generally well oiled, shinny gear teeth with no sign of water droplets or rust.
3. Also, verify that you actually have brass synchros and not the Porsche-type (don't assume that your BMW has it's original gearbox). There will be a seven digit serial number stamped into the top edge of the bell housing between the two bolts (through the bell housing into the block) directly behind the cylinder head.

In all 6 cylinder, 4 speeds and both 4 & 6 cylinder, 5 speeds

1. Pull both fill and drain plugs and inspect for any rust or metal fragments and the general condition of the gear teeth.
2. Spin the input shaft for free movement.

10. If my core isn't rebuildable?
If it fails the above tests, first call us and get a second opinion. If it proves to be totally unrebuildable, you can either pay the core charge or try to locate a suitable core from the salvage yard or the classified ads. Almost all cores have some value, depending on the extent of the damage. In these cases, it's best to ship it to us for evaluation first. If you decide to pay the core charge, we will treat it as a deposit for 30 days giving you the opportunity to locate a good core(s).

Note: Any rebuildable 4 speed will suffice as an exchange core for any 4 speed "Ultimate Transmission" and likewise for 5 speeds.