FoT'ers
A few years ago an acquaintance did a series of back-to-back comparisons of
differentials at Sears Point in Improved Touring 240 Z's which I and other of
his customers were then racing. Said acquaintance was a suspension and
development guru and a very capable test driver whose business was located at
Sears and he typically spent several days a week actually on the track. As an
aside, the ability to pull a car off of the track, into your shop, and onto
your setup platform is almost too cool for words.
His experience, with that type of car, at that track, indicated very little
difference in the several LSD options available then for diff's, including a
Gleason-Torsen (torque sensing type which I am told is similar to the Quaife),
and your basic welded units, especially when the car and the driving style was
adjusted for the attributes of each.
His bottom line was, with the possible exception of a low HP car or at tracks
with long sweeping corners where the drag of the welded unit might be an
issue, the options yielded very little measurable change on the stop watch;
spend your money on seat time. Having driven some with Detroit lockers, the
Gleason-Torsen's and mostly, with the welded types, I would agree the Gleason
is the smoothest feeling. Smooth is a relative term however when you're
talking Triumph. There is something to be said for the consistency, lap after
lap, of the welded diff, which is not the case with some of the other options.
>From my very amateur perspective, there's nothing worse than trying to figure
out if it's you or it's something obscure like the breakaway torque on the
rear end that is making things feel so goofy.
The welded approach calls for some extra effort on the turn-in, although that
may be lessened with some toe-out at the front end (which I suppose might hurt
on a track with long straights which Sears doesn't have). Also, I would
suppose that a good driver might do a better job saving the tires if he was
not having to throw the car around as welded diffs seems to require, although
from what I hear about Vintage Hoosiers (compared to slicks that you can
overheat) that may not be an issue.
In terms of performance, I think I'd put a bigger priority on optimizing the
final drive for each track (which means having several diffs if you travel)
than the possible improvement of a limited slip device. When you want several
different final drive ratios, it's a lot less expensive to only buy the
various ring and pinion ratios and weld up the spiders, rather than paying for
all of that plus an expensive diff for each set.
All of that said, this is clearly a question for which there is no right
answer. But hey, I got to think about the sunny summer days of racing for a
while I wrote this.
The best of the season to all, Dave Talbott
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