Evolution of the BMW shift Mechanism
The Early Years
The very early cars used this mechanism. Most of the time the shift arm was an aluminium casting attached to the transmission . the selector rod was a yoke style rod and the coupler had 2 small pins
The Shift arm in the early 1600 were aluminium castings bolted to the transmission and very well supported. This allowed the mechanism to behave like if it was built inside the transmission rather than hanging on its outside.
However the mechanism was outside the transmission exposed to the elements and noisy.
Notably the selector rod used a yoke. With a pin in double shear on one end of the rod. The pin was much larger then than it is now and was needed because the nylon surfaces used for friction had very poor life. Thermoplastics available then were pure nylon and wore out rather quickly. The pivot ball was a steel ball much more durable than today's nylon balls and the lever was a 2 piece job with replaceable innards.
The transitional period 73 through 76 saw a change in the mechanism. Mostly improved that style of shifter lasted through 1985
Gone is the aluminium bracket bolted to the transmission. This now replaced by a sheet metal bracket connected to the back of the gearbox using isolation blocks.Rubber filled aluminium connectors . while this has the advantage to be quieter because of the give of the rubber they also allow the rear of the bracket to droop down forcing the BMW engineer to devise a rear rubber support to counteract that unfortunate characteristic.
Notably however and through the years that double shear selector rod having outlived its reason for being is now been replaced with a single shear rod. Plastics have improved and the nylon used is of higher grade. At first the pin going through that plastic is of a larger diameter to better spread the load on the bushing but as of 83 it shrinks down to the current 10 mm dimension as the Nylon bushing is now reinforced with fiber.
This is not a bad shifter when new. Mostly because the bracket is connected to the transmission with two bushings 3 inches apart and is therefore prevented from rotating along its axis. pivot ball is also steel and the connection between the outer and inner levers reasonably rigid.
A drastic change happened in 1986 with new materials and cost cutting
First the great steel stamped bracket was replaced by a cast aluminum job poorly supported at the front . Then the lever dropped its replaceable innards and became a 2 piece bonded unit. The rear support also changed for the better this time.
It could have been a great setup. The bonded lever evolved in 1988 to become what was perhaps BMW greatest lever. ( steel ball, rigid connection, reinforced bottom upper handle) And the aluminium bracket metallurgy also improved as did its connection to the transmission. Sadly as one got better the other got worse. Sometimes in the mid nineties the shift lever production switched from Germany to France, the rigidity of the upper to lower ever connection switched from rigid to mushy and the steel ball switched from steel to nylon. e46 ended up with the worst shifters ever. Some enlightened soul though developed the best rear bracket mount ever . A tank of steel and rubber still in use today.
BMW sees the light and improves the shift arm based on the lessons of the past. The lever continues its long decline. Front coupler improves to mirror the AutoSolutions coupler.
2006 sees the birth of the double bushing shift arm bringing a lot more stability to the bracket where the shifter mechanism resides. To be fair the move started in the early 2000 with 2 bushings per arm near to one another but it was only after 2006 that the arms sported bushings several inches apart and the resultant rotational rigidity.
Sadly the lever went the other way. Inner lever bonded to an outer lever in a rather loose manner and the ubiquitous nylon pivot ball.
The front coupler is no longer a welded unit. it is now built out of one piece of steel a year or two after we built ours.
As stick shift cars become a true afterthought, the mechanism is modified to provide manual control to vehicles that are designed as automatics or to be paddle shifted.
This period retains the poor lever from the previous generation bent and re-bent at bizarre angles in order to fit newer shift consoles. The cars also retain the great rear shift arm support bushing.
Shift brackets themselves also evolve in shapes bizarrely formed to clear obstacles that the earlier cars did not have. Shift couplers adapt with varying degrees of offset to accommodate the AWD transmissions and are now sometimes welded.
Selector rods are now solid rods in some cases with a pressed pins just like the AutoSolutions rods. Others follow the same construction techniques established in the early eighties but the shapes are bizarre