Downshift from 4th to 3rd. The shift effort at the knob is redirected by the lever and multiplied by the ratio A/B. this multiplies the force by about a factor of 6. A 15 Lbs. force becomes a 90-lbs. force at the other end of the lever.
The selector rod transmits this 90 Lbs. force almost completely to the shift rail. To be precise, this force is reduced slightly since the selector rod is not always in line with the shift rail.
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.
Past the shift rail the shifting force continues its travel and has to overcome the resistance of the shift rail detent (a) and the resistance of the synchronizer sleeve detents (b). Finally, the majority of the force is spent fighting any selected gear’s reluctance to align itself with the synchronizer sleeve (c).
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Path of the shifting force |  |
Static resistance withintransmission |
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Clearances in External Linkage |  |
Dynamic resistance within transmission |
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Other Clearances |  |
The Ideal Shift Linkage |
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