Allen,
FYI The 3.9 rears are available from Bob Bowie all day long for $59. You
can spot them for sale on ebay.
Keith Pennell
> Thanks for the replies on this thread.
>
> I dug into this a little more, and went to the 1956 Parts list
(PUblication
> 1050, ed2). I now realize that the 140 mph spedometer (7H1751), rated in
the
> catalogue at 1180 rev/minute, equates with a special axle ratio of 3.6,
> against the 120 mph speedometer (3H3061) which is rated at 1325 rev/min
for
> the stock 4.125 stock axle ratio. The conversions are not identical
(1180/1325
> = 0.891:1 and 3.6/4.125= 0.8727), but I get the general idea.
>
> I know understand that some later BN** pumpkins are rated at 3.90 and hear
> some BN2 owners have gone to this for longer legs without perceivably
> sacrificing acceleration. This has been recommended by atleast one M owner
in
> prior correspondence. Our engine is really hoofy (lightened flywheel,
0.60"
> oversized rings from PO, headers, etc., so I wouldn't mind some longer
gears
> in 2nd and 3rd gear. The majority of our drving is on unengineered winding
New
> England secondary roads, where overdrive is seldom needed. With just a
little
> more speed in 4th we could do without it almost all the time.
>
> If I were to make the conversion to 3.9, this would reduce the speedometer
> error by roughly half (3.9/4.125=0.9454). If we do this, can the
instrument
> services adjust the other half without changing the spedometer gears?
>
> Any thoughts on the 3.90 conversion or on the range of adjustability of
the
> speedometer mechanism would be appreciated.
>
> Also, are 3.6 rears available for the BN2 pumpkin?
>
> One of the responses to my last inquiry mentioned a BJ8 conversion to
3.54"1
> rear. Is that something that can be done with a BN2 axle housing?
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