Derek,
Thanks for the information on the Getrag Transmissions. I
have taken the liberty of adding some more transmissions to
your fine table, and doing one more calculation, the gear
'spacing'. This is expressed as the percent ratio change,
which is the same as the percent change in rpm on a gear
change. The higher the percentage, the greater the rpm drop
(or rise in down-shift), regardless of how quickly you
shift, as this is strictly mechanical. The greater the
ratio change, the more you get off the flat part of the
torque curve. The main advantage of multiple speeds is to
reduce the drop in rpm to keep 'on the power curve'. The
later model non-sports car 5 spds have very high 5th gears
for economy, not performance. The Getrags seems to be more
of a sports car transmission, where a 20% change is about
the norm.
It should be noted that the Tiger MkII "wide ratio" isn't
much "wider" than the "close ratio", in that he gear spacing
is relatively evenly spread, but starts at a lower point,
giving much more acceleration in first without putting a
3.55 rear end in it, and killing your 4th gear behavior.
I hope I've made that clear enough, this is not an intuitive
concept for most. With a choice of the rear end ratio and
tire diameter, road speeds at shift points can easily (?) be
determined. I'll post the formula's for those that are
interested. The "% Change" is simply =
1- (Higher Ratio/Lower Ratio). It the same percentage the
RPM changes.
Hope the Table fits the line breaks.
First
Second Third Fourth Fifth
Getrag 265 3.82 (42%) 2.20 (37%) 1.39 (28%)
1.0 (19%) 0.81
Getrag 265/Sport 3.44 (42%) 1.98 (36%) 1.26 (21%) 1.0
(27%) 0.73
TREMEC TR-3550 3.27 (39%) 1.98 (32%) 1.34 (25%) 1.0
(32%) 0.68 (Torque 400+ Lb-Ft)
T-5 Original 3.35 (41%) 1.99 (33%) 1.33
(25%) 1.0 (32%) 0.68* (Torque 265 Lb-Ft)
T-5 World Class 3.35 (41%) 1.99 (33%) 1.33 (25%)
1.0 (32%) 0.68* (Torque 300 Lb-Ft)
Top Loader (close) 2.32 (27%) 1.69 (24%) 1.29 (22%)
1.0 (Torque - Humongous)
Top Loader (wide) 2.78 (31%) 1.93 (30%) 1.36 (26%)
1.0 (Torque - Humongous)
It should be noticed that the gear spacing between the
"close" and "wide" Top Loaders is nearly the same, and
either is more evenly spaced (closeness) than any of the
others. That "wide ratio" 2.78 first, with the stock 2:88
gears is a great combination for a Tiger.
Picking a rear end ratio and tire diameter allows speed/rpm
in each gear to be determined, but I'll leave that for
another time.
Steve
--
Steve Laifman < Find out what is most >
B9472289 < important in your life >
< and don't let it get away!>
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