We Build Three Types of Shifters... Well... sometimes Four
The Complete Shifter class is an evolutionary design. The factory geometry remains but the construction of the various components is upgraded, the clearances of all the joints are tightened and the throw shortened. The feel of this entry lever shifter is night and day compared to the stock shifter. Price is generally between $250 and $300 and it is offered on most cars but only if it can deliver the night and day promise.
The Ultra Shifter ( often referred to as Ultimate) is a redesign of the factory shifter and not only replaces all the components but changes the geometry of the mechanism. This is the first step to a hand fitted mechanism. It is a substantial improvement of our complete shifter especially in the gated feel of the pattern. Price is generally between $399 and $449 and it is offered on a several models. Sometimes this class includes a new shift arm , other times a different pivot.
The AutoCross Class is a beast. It represents the latest upgrade in shifter design . Equally at ease on the track and in traffic jams. It has none of the noise, vibrations or harshness of a full on race shifter and shifts with a couple of fingers while commuting. The AutoCross design maximizes rigidity, control of the pattern and ease of shifting. It is slicker and more precise than the Ultra and sadly more expensive as well at $450 to $540. Sometimes it includes a new shift arm other times a better shift arm retention mechanism. Is it worth it? You be the judge . Available on a very limited number of models.
This category includes all three classes of shifters. Complete, Ultra and AutoCross plus a few hybrids. Mostly this category covers BMW models that are not particularly common as shown in the AutoCross class of the z3M shifter pictured above. It also includes simpler shifters products like a plain jane complete shifter for a 2002 4 speed or an adapter to raise the pivot point on e21 323i. And sometimes shifters that make an esthetic statement.
HOW IT WORKS
And What the Shifter Really Does
A major fallacy is that a short shifter will make you shift faster than one with a long throw. In reality it matters not if your shifter is a stock shifter or a super short shifter. What matters is the quality of your shifter. In other words how little the shifter gets in the way of shifting gears. As this section explains, it is the transmission that is the ultimate limit to the shifting speed. Things like lubrication, efficiency of synchronizers and simplicity of the mechanism inside the transmission are the main determinants of the ultimate shifting speed. The shifter itself is only the contraption that connects the human element (your hand and mind) to the machine (your gearbox) and as such that contraption is more hinderance than help.
Generally a shifter will shift faster if it allows you to shift using muscle memory so that the same amount of effort is spent on every gear and if it allows the gates for each individual gear to be located at the same place in the shifting pattern time and time again and finally if the effort it requires from you is used moving gears rather than to deforming components.
This is a Simplification of the BMW Mechanism
Take a peak at the above Diagram while you downshift from 4th to 3rd. The shift effort at the knob is redirected by the lever and multiplied by the ratio A/B. This ratio is the mechanical advantage of the shift lever and multiplies the force at the knob by a factor as high as 8 on some cars and as low as 4 on other . A 6 to 1 factor for instance, is quite advantageous. It multiplies the force at the knob by 6 so that a 15 Lbs. force at the knob can become a 90-lbs force at the bottom of the lever. A 4 to 1 factor is less advantageous and only multiplies the force at the knob by 4. Why does the A/B ratio vary from car model to car model. Two reasons we think. First is the intended purpose of the car. A 5 series is typically a daily driver with a requirement of an easy comfortable shift whereas an e30M3 is a racer with little to no aspiration of being a grocery getter. As such the A/B ratio on an 85 535i will be considerably greater than that of an 88M3 even though both cars use the same transmission. Second is the design of the transmission. The 88M3 transmission was originally designed sometimes in the sixties whereas the e92M3 transmission was designed about half a century later. Both cars are sport cars but the newer transmission is more efficient at transmitting the force applied to its shift rail than its older sister and therefore can make use of a lower A/B ratio. As an aside the greater the mechanical advantage the more travel at the shift knob. Short Shift kit anyone?
Moving on … and back to our 6 to 1 ratio which generates 90Lbs of force at the selector rod when 15Lbs is applied at the knob. The selector rod transmits this 90 Lbs. force almost completely to the shift rail that traverses the transmission. To be precise, this force is reduced slightly since the selector rod is not always in line with the shift rail*.
Past the shift rail the shifting force continues to propagate and has to overcome the resistance of the shift rail detents (a) and the resistance of the synchronizer sleeve detents (b) and various frictional resistances between the moving parts of the gearbox and its casing. Finally, most of the force is spent fighting any selected gear’s reluctance to align itself with the synchronizer sleeve (c).
*The resultant force on the rail is actually 90Lbs multiplied by the Cosine of the angle of the rod to the rail. The greater the angle the smaller the resultant horizontal force at the transmission rail. A 60-degree angle has a cosine of .5 and will effectively reduce the force by half.
In practicality however the angle of the selector rod is around 4 degrees and rarely exceeds 10 degrees. The cosines of these angles are respectively .997 and .984 so the resultant force travels almost intact to the rail.
What's With This Shifting Effort ?
A Little of it is Spent Moving Springs and Detents...
A Little Friction Goes a Long Way
Red Dots show the various springs and detents and the spots where friction occurs during a shift. A transmission that has been running low on oil will require undue effort. What's worse is that the damage may be permanent because the springs will jam in their holes and the friction surfaces will gall . Once this happens, the damage is done and adding fluid at that point will not unjam the springs or re polish the friction surfaces. Keep an eye on your fluid level.
TRIVIA OR USEFUL KNOWLEDGE : No doubt you have noticed how shifting in the same gear over and over when the engine is off and the car stopped is easier the 2nd time or third time around? The why is because the first time you shifted you overcame some of the static resistance of the transmission by aligning the synchro of that particular gear. Need more details? Read on:
The shifting force is applied against the shift rail and pushes it forward. The shift rail rubs against the case and some of this force is lost in heat. Another portion of the force activates various detents. Here, spring loaded detent balls climb on a ramp cut into the shift rail and overcome the resistance of small springs (1) Similarly the shift rail activates shift forks that in turn move the synchronizer sleeve compressing other detent springs (2) in the sleeve body and allowing clips in the body to retract.
However most of the force is used by the synchronizer-sleeve teeth meshing with their counterparts on the selected synchro-meshed gear (3).When the transmission is not rotating that resistance (3) needs to be overcome only once. It will not reappear until the transmission is rotated and the gears are no longer aligned. This leaves only the two smaller resistances (1) and (2) to overcome on a second and third shift hence the ease of shifting in the same gear when the vehicle is stopped.
But Most of it is Used Moving Gears
Where Most of it Goes
It is usually harder to downshift than upshift. On an upshift the synchronizer grabs the spinning gear and slows it down until it meshes. On the downshift it must accelerate it and force itself into it. increasing the rotation speed slightly through double clutching creates a virtual upshift situation and makes for an easier engagement.
To fully understand this one must look at the design of the synchronizer assembly used in BMW transmissions.
Imagine two sets of gears resting flat on the table. When the peaks of one gear are lined up with the valleys of the other then both gears can mesh effortlessly. However if they do not line up then one gear has to rotate slightly in order to mesh with the other. In order to do so the teeth of one gear will simply push against the teeth of the other and rotate it slightly while they are meshing together. Easy to do when the gears are not turning at different speeds. What the Synchronizer does is exactly that it aligns peaks and valleys so to speak ( over simplification but this is not a class on manual transmissions). To get the synchronizer to do that requires effort. The bigger the gears and the higher their speed differential the more effort is required for the synchronizer to grab the rotating gear and slow it down or speed it up till it meshes. Moreover, if the synchronizer has "slippery hands" and cannot cut through the lubricating film in which the gear is then it will be even harder for it to even grab that rotating gear in the first place let alone change its speed.
Therefore the bigger the gears in the transmission the harder it is to move them and a worn synchronizer will have a harder time doing that than a newer one and that the transmission oil in which the gear rotates can cause resistance a well. The first is a given .gears in an e46M3 will require more effort to move than those in a 2002. The second is dictated by the condition of one's transmission requiring a rebuild to alter. The third can be experimented with at reasonably low cost.
Building a Short Throw Shifter
In its Simplest Form all That is Needed is to Increase One Arm of the Lever
As you may have read above , the BMW lever gives the operator a mechanical advantage. This advantage is required to overcome resistance inside the transmission that may be due to transmission design or wear or a combination of both. Previously we used the example of a lever with a 6 to 1 mechanical advantage so that a 15Lbs effort at the knob would generate 90Lbs of force at the selector rod and consequently at the shift rail which is the business end of the transmission. What we have just described here is a class 2 lever. Lets assume that 90Lbs at the shift rail is required to effect a shift. The greater the distance B is in the below diagram the smaller the mechanical advantage of the lever and the more effort is required at the top of the lever to generate the required 90lbs at the shift rail. Conversely the smaller B is the lesser the required effort .
However, shifting from one gear to the next requires that the shift rail moves a given distance. Say for argument sake that the shift rail needs to move exactly one half inch for fourth gear to be engaged. On a 6 to 1 mechanical advantage lever that pivots around a ball as shown in the above picture, the top of the lever needs to move backwards 6 times more than the bottom of the lever is moving forward. If the bottom of the lever needs to travel forward one half inch then the top of the lever needs to move backwards 6 times as much or 3 inches. So if the distance from the pivot to point A is 6 inches and the lever is a 6 to 1 lever then the distance from the pivot to point B is 1 inch.
As you may have read above , the BMW lever gives the operator a mechanical advantage. This advantage is required to overcome resistance inside the transmission that may be due to transmission design or wear or a combination of both. Previously we used the example of a lever with a 6 to 1 mechanical advantage so that a 15Lbs effort at the knob would generate 90Lbs of force at the selector rod and consequently at the shift rail which is the business end of the transmission. What is described here is a class 2 lever. Lets assuftme that 90Lbs at the shift rail is required to effect a shift. The greater the distance B is in the below diagram the smaller the mechanical advantage of the lever and the more effort is required at the top of the lever to generate the required 90lbs at the shift rail. Conversely the smaller B is the lesser the required effort .
However, shifting from one gear to the next requires that the shift rail moves a given distance. Say for argument sake that the shi
We Hold this Slop to be Self Evident
In Green are the areas of greatest concern. The basic stuff so to speak. If these areas are not addressed first no amount of money will get you a decent pattern. First make sure that these clearances are minimized and that they will stay low for a long time.
Below the Shift lever is the First Joint...
It consists of a cylinder with a hole in it that is lined with a friction friendly material and a harder cylindrical pin tightly filling that hole and able to rotate in the hole