From RonStygar_at_aol.com Sat 17 1999
Date: Sat, 17 July 1999
Subject: Lets check out the selector rod joint vertical off axis force in my
My '96 328is uses the same transmission as the M3. With the help of Ken
Dobyns, I've calculated the vertical off axis selector rod joint force stock,
with the M-Z3 lever and with the M-Z3 lever using the ERK. Will be doing the
same for the horizontal off axis force soon.
Keep in mind that whatever percentage reduction in shifting throw you
achieve results in the same percentage increase in shifting force. It's just
lever physics. No magic here.
The stock shift lever in a E36 M3 has a ratio of 4.86:1. The M-Z3 shift
lever that people replace it with to short shift their cars has a ratio of
3.34:1. This results in a shifting throw reduction of roughly 31.3%. The
shifting force goes up the same 31.3% amount. 3.34/4.86 = .6872427. 1 -
.6872427 = .3127573.
.3127573 x 100 = 31.3%.
Another example, which takes into account the vertical off axis force.
Vertical off axis force is the force felt at the transmission selector rod
joint if the front and rear selector rod pins are not exactly inline. See
the above vertical off axis force diagram. As mentioned above, the stock E36
M3 shift lever has a 4.86:1 ratio. The M-Z3 shift lever has a ratio of
3.34:1. Say the force at the base of the shift lever is 26.51 pounds to move
the transmission shaft (this is what it was in my '96 328is which uses the
same transmission as the M3). With your stock lever the force at the shift
knob would be 26.51/4.86 = 5.4547325 pounds. With the new M-Z3 lever WITHOUT
THE ERK it would be 26.70/3.34 = 7.9940119 pounds. Still with me? WITH THE
ERK it would be 26.46/3.34 = 7.9221556 pounds which is .0718563 pounds less,
which is less than a 1 percent reduction in force felt at the shift knob
using the ERK.
Replace a shift lever for more info.
RonStygar_at_aol.com FLY BMW Marlborough, CT
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