[Healeys] OD Longevity

Alan Seigrist healey.nut at gmail.com
Mon May 16 04:02:19 MDT 2016

Yep, the OD on my BJ8 has probably seen 150K or even 200K miles (not
sure).  Never touched it, still works like a champ.  My original 32% OD on
my early BN1 is similar... never rebuilt.

My feeling is they are quite similar to old three speed automatic
gearboxes, and as long as you treat them with respect, and keep oil in
them, they will last forever.

On Mon, May 16, 2016 at 1:04 AM, Bob Spidell <bspidell at comcast.net> wrote:

> Listers,
> I've always been a bit in awe of the Laycock De Normanville overdrive
> units as fitted to our Austin-Healeys.   To me, it's a wonder of
> engineering elegance and simplicity--well, except for the electricals,
> maybe--and as it's an 'axial' design there are no significant side loads to
> wear out layshafts/gears and bearings. However, all things have a life span
> and I'm wondering what is the typical life for the A-Series--I believe
> that's what's in my BN2 and BJ8--OD units under 'normal' (non-racing)
> usage?  The unit in my BJ8 has over 190K miles on it and AFAIK it has never
> been overhauled, and I'd hate for it to die on one of my long road trips as
> we inevitably spend hours on straight stretches of interstate highways (I
> do have a 3.54 rearend, which would make things a bit more tolerable, but
> the 22% reduction in RPMs is hard to beat; except maybe with 28%).  I've
> used Redline MT-90 in the gearbox/OD for the last 40-50K miles or so
> and--some will think this is blasphemy--I only change it out every 20-30K
> miles (I don't buy into the 'use non-detergent oil so the all the sludge
> will drop to the bottom' theory, when I change out the syn oil I note the
> oil is clean and light-colored, and that there is finely-ground brass shake
> suspended in the oil but it is so fine you can't feel any grittiness at all
> if you rub it between your fingers; and note that some of the best
> greases--lithium, molybdenum, etc.--are finely ground soft metals suspended
> in oil).
> Anyway, what's the collective wisdom on this: run 'em until they quit, or
> rebuild them at 100/200/300/?K miles as a precaution?
> As usual, TIA.
> Bob
> ps.  I'll keep using 74W-90 in the diff as recommended by y'all.
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