Ken Nuelle writes:
>In a message dated 12/11/98 10:50:53 PM EST, bk54@erols.com writes:
>
><< Andy Mace wrote,
>
> >> To be sure, though, raise the rear of the car and place it on stands.
> Temporarily stop one rear wheel from moving (have someone hold it, or
> tighten the brake adjuster). Slowly turn the free wheel through one
> revolution while someone counts the revolutions of the driveshaft at the
> input flange of the rear axle (you could chalk or otherwise mark the
> flange to make the counting easier). If the flange/driveshaft turns just
> under four times, it's 3.7; if just over four times, it's 4.1. <<
>
> Actually, with the opposite wheel immobilized the drive shaft will spin
> twice as fast. 7.4 turns if the axle ratio is 3.7, or 8.2 if it's a 4.1.
> >>
>Actually I think Andy is right here. I tried this on my car without
stopping
>one wheel and got about half the expected ratio. 1 turn of the roadwheel
was
>about 1.9 turns of the prop shaft. Scratched my head and moved on.
>
>Ken Nuelle
>58 TR3A
>62 TR3B
>64 TR4
Actually, There is a factor of two here but it is in the other direction.
If you immobilize one wheel and rotate the other wheel one time the
drive shaft will rotate a number of times equal to one half the axle
ratio.
I did this on my TR8 (I suspected someone might have fitted a 3.36
axle on my car) and the axle rotated a little more than 1.5 turns.
This, however, was inconclusive (and required a little math (1.5?
x 2) so I thought "Why not rotate the tire through TWO revolutions?"
Doing this gives more resolution and the drive shaft revolution count
translates directly into the ratio!
Then I went one better (more anal retentive?) and rotated the tire
20 times and counted just short of 31 drive shaft revolutions thereby
confirming that the axle in my car has a ratio of 3.08 which is
stock on this car.
Hope this information helps.
Dave Massey
57 TR3
71 TR6
80 TR8
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