In a message dated 01/07/01 9:50:20 AM Pacific Daylight Time, kmr@pil.net
writes:
> Very correct. The advantage in every aspect, except strength, goes to a
> stock O/D gearbox. Typically the O/D boxes have a better top ratio than the
> 5spds do. I see no competition advantage to using a 5spd over an overdrive,
> you can modify your overdrives to work in all gears... giving you eight
>
I'd beg to disagree on this point. Use of the OD in lower gears might be
useful on the street (I used to use 2nd OD in my TR3 to avoid going up to 3rd
for traffic), but the sizing of the OD components is not such as to allow
that use in competition without ripping up the friction surfaces.
Yes, you can modify the OD to take more torque, but then in racing use you
have less, nor more need for such.
This may sound contradictory, but bear in mind that the gear splits are
around 1200 rpm apart on an early CR gearbox at around 6000 rpm. So if you
shift at 6200 rpm, for instance, you drop to about 5000, right at the torque
peak on a racing engine. Any additional ratios in between those would just
slow you down, as you must not do a full throttle upshift into an OD ratio.
Other than the odd corner that slows you down a bit more, my engine during a
race is between 5000 and 7200 or so for the full 30 minutesof the race, using
2nd, 3rd, 4th, and on the straight, 4OD.
The early box with 4 bearing layshaft is strong enough for almost any use to
which you might wish to put it; I have had a brand new set of the MGC all
synch straight cut close ratio gears (presumably long unavailable) on the
shelf for the last 20 years, in case I started trashing the smaller gears of
the early box, without having to unpack them. Maybe I'll build a V8 some
time, and need them, but otherwise I shall continue to use the (to my way of
thinking anyway) nicer early box.
Bill
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