Shear Selector Rod
This part fits:
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
One significant wear area that has never been addressed previously is the
and ovalization of the linkage connection points at the transmission and the
shifter'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.
The looseness and slop are magnified by the leverage-multiplication effect of
the shift lever itself. The result is an in-gear shifter "free play"
of 3/4" and up to 1" in either direction, over 35mm total.The
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). The 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 a UUC EVO3 shifter.
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 miles.