You either have a tach problem or you have a 4.88:1 diff if it is a
midget. I'm not sure about the available ratios for a B.
Both are possible.
You could check the tach easily enough by using a combination
dwell meter/tach tune up instrument. You'd need a 2nd person to
sit in the car and hold a steady 4000 rpm.
Mike
-----Original Message-----
From: Michael Graziano <mgrazian@ltcm.com>
To: MGList <mgs@autox.team.net>
Date: Wednesday, June 24, 1998 12:47 AM
Subject: Differential Calc Update
>OK. I sat at home with my manuals, and my MS Excel and did
>the math.
>
>My tires are P155/70R13's. The wheel radius is 11.050
>inches (and therefore, the wheel circumference is 5.79
>feet. So at 4000 rpm, the car should run the following
>speeds:
>
>3.72 differential: 70.70 mph
>3.90 differential: 67.43 mph
>4.22 differential: 62.32 mph
>
>So, I'd have to have a 5x to 1 gearing in my differential
>to explain 50mph at 4K rpm. Definately not the case. Where
>to next?
>
>BTW - when doing the calc, using the 3rd gear ratio of
>1.433:1, I'd be doing 50 mph @ 4K rpm. BUT I KNOW I'M IN
>4TH.
>
>Can it possibly be a tranny problem?
>
>Mike
>
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