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Re: speedometer conversion

To: Blue One Hundred <international_investor@yahoo.com>
Subject: Re: speedometer conversion
From: John Harper <AH@jharper.demon.co.uk>
Date: Wed, 29 Sep 2004 08:23:10 +0100
Alan

You may say that I am going into too much detail and I agree that from a 
rear axle ratio point of view you are correct.

However pity the chap who is trying to remove his hubs on the later 100 
Hypoid 5 stud axle where both large nuts are Right Hand thread! He might 
be expecting R.H. and L.H. threads as per the later cars.

Also one needs to watch out for oil fillers. Two is obviously not a 
problem but if you try to fit a later 'pumpkin' into a late BN1 casing 
you will end up without an oil filler plug!

All the best

>The rear axle is exactly the same for late BN1s all
>the way to BJ8 (only difference are some variance in
>the brake drums).  That means you can use Mike
>Lempert's 3.54:1 gear in your BN2 no problem.  Go
>order one quickly... who knows how long it will be
>until they are available again.
>
>http://www.lempertgroup.com/gears.html
>
>I, on the other hand, may have to settle for the Cape
>3.66 gear for my early BN1.  $$$$$
>
>Cheers,
>
>Alan
>
>'53 BN1 '64 BJ8
>
>
>
>--- "Allen C Miller, Jr." <acmiller@mhcable.com>
>wrote:
>
>> 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?
>
-- 
John Harper

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