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Re: SPIT OD

To: british-cars@hoosier, mit-eddie!probe.att.com!gerry@EDDIE.MIT.EDU
Subject: Re: SPIT OD
From: muller@Alliant.COM (Jim Muller)
Date: Tue, 21 Apr 92 11:28:15 EDT
Gerry tells us:
>Now my Scimitar has 150 HP and 180 lbs/ft of torque, which is somewhat
>more than a Spitfire, but on the other hand the overdrive unit is meatier
>too !!!!
>BTW: when I used the OD in 2nd gear, it would engage/disengage more
>abruptly than in 3rd & 4th, I guess putting strain on the unit.

Someone else pointed out the danger of using OD in too low a gear.  Perhaps
one should avoid using the OD in 1st or 2nd even if it can be engaged.
On the other hand, it certainly is easier to wire up a relay off the
backup light than to fabricate a bunch of lost parts.  At least you get
some protection against one of the several ways you might abuse it.

I don't know that shifting abruptly is a problem.  The various manuals and
such say to shift the OD while under full power, and when it shifts, the
result is, shall we say, instantaneous.  But that seems to be the prescribed
mode of operation, not that the various B-L manuals ever were that accurate.

Just curious, though, wasn't the later Spitfire OD the J-unit (or whatever
the letter was) the same as used on the later TR-6's?  If so, it is very
unlikely that the Spitfire motor can over-torque it, even in 2nd (and 1st
would be kinda' silly).

Except of course that the 1500 is such a monster that it will snap the
teeth right off the planetary gears... :-)

Jim Muller
(Hey, I drove Percy in to work this morning, top-down alla the way.  Warm
weather has finally arrived in New England.  I expect tomorrow it will
be either (a) 40 degrees and rainey, or (b) 90 degrees with 90% humidity.)



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