Paul Hunt wrote:
> > BTW, on Triumphs, they used to allow OD on 2nd, 3rd, and
> > 4th. Great for people that wanted rowing practice, but unless
> > you were in stop and go slowly moving traffic, when 2 - 2OD
> > could be useful, there really wasn't much point.
>
> Obviously the MG has more torque that the Triumph... but I
> *thought* it was only in 2nd on a 3-speed box i.e. still the top
> two gears. It was not allowed on 1st and 2nd in the MG for
> the same reason that it was removed from 3rd on the factory
> V8 i.e. the torque reversals are potentially damaging.
Paul, Bill was referring to TR3s, TR4s, TR5s and yes the TR6 which, when
equipped so, had A type overdrives (up until about 1972). It was standard
at that time to allow 2nd gear to operate in overdrive, in addition to the
normal 3rd and 4th gears. Since, there are no part number changes for the
transmission top covers for the UK PI TR5/6s, it would reason that they too
were allowed to operate OD in 2nd gear. So it isn't that the MG has more
torque (which it doesn't) than the TRs, the TRs simply did not use D and LH
type overdrives which are not of the specification as the A type.
The factory Triumph rally cars had operational overdrive available in all
forward gears. Neil Revington's current TR4 rally car also is setup to
function this way, without any adverse effects. The A type overdrives are
incredibly tough, only surpassed in their strength and bulkiness by the P
type overdrives used in Bentley's and Roll Royces (as well as a great deal
of commercial trucks).
In my experience, 2nd Overdrive can be useful, but in limited circumstances.
I would use it when there was slow moving, but a constant flow, on the PA
Turnpike when I traveled that route to and from work. Shifting gears
becomes tiresome after a while in those conditions, so it was more of a
convenience than a necessity.
About upshifting while overdrive is engaged, Revington also sells a kit
(albeit for TRs, but probably suitable for any Laycock overdrive) that he
terms an Overdrive Logic Device. It will automate the function of
disengaging overdrive while upshifting or downshifting and then reengaging
when you've settled on which gear you wish to be in. It isn't terribly
expensive, so it may be worthwhile for some people who use their cars
heavily as daily commuters.
Kai
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