While producing a "short" shifter, our more important goal
in improving the BMW shifter assembly is to increase the precision and
smoothness of the overall operation.
One significant wear area that has never been addressed
previously is the wear and ovalization of the linkage connection points at the
transmission and the shift's lower pivot.
In the original BMW design, the connection at both ends
has a large injection-molded plastic bushing. We already know how badly plastic
wears in an automotive application, and these areas are not an exception. The
design of the selector rod has a pin at 90° to the main rod, which exerts a
tremendous amount of leveraged force on the selector joint bushing from one side
(known as a single shear force). The result is a steady deformation of
the bushing, resulting in looseness and slop in the entire mechanism.
New Page 2
A temporary fix is to simply replace the
selector joint. Unfortunately, this is only a temporary fix as the new
joint's bushing will exhibit the same rapid deformation. To permanently
fix this, a change in the fundamental design of the pivot is required,
changing the assembly to a double shear system with the UUC
Double Shear Selector Rod (DSSR).
DSSR redistributes the torsional forces from the pin/bushing interface
to the complete face area on both sides of the selector joint. By taking
advantage of the strength of steel in the DSSR and the body of the
joint, the problem of deformation is eliminated and the movement of the
selector rod correlates directly to movement of the selector joint - the
only "free play" movement remaining in the shifter assembly is from
within the transmission itself. In-Gear "free play" is
reduced to approximately 10mm total when used with the UUC.
The original BMW shifter
and all other aftermarket shifters (except UUC which uses
deformation-free bearings) contain a plastic bushing similar to the
selector joint, and the exact same wear and ovalization causes those
shifters to get sloppy. The DSSR permanently fixes these shifters also.
The DSSR is compatible with all brand shifters, whether
original BMW or other-brand aftermarket.
When used with the original BMW shifter or
other aftermarket shifters, the amount of "free play" will be greatly
reduced but varies by shifter (flexation of the shifter shaft
contributes to the total "free play" travel).
No Other Solutions
While there are other replacement selector rods sold in the
aftermarket (including "no tolerance" brass and "heavy" selector rods), none
of them will get rid of the slop and "free play" in the BMW shifter assembly.
These alternate products are not actually improving the shift feel at all, but
are simply rods with alternate geometry (either bent or twisted), an
accommodation to make the "universal fit" aftermarket shifters fit properly.
These other aftermarket shifters, even with their "heavy"
selector rods, will still be as sloppy as the original BMW shifters they are
replacing. While the throw may be shorter, the precision of the assembly is no
better than a new BMW part, and will develop the same slop within a few thousand
- 1997-2003 528i/530i (manual transmission)