Brent -
Put the car in 4th and push (plugs out helps). This method also corrects
for differences between measured diameter of tire and actual rolling radius
and eliminates backlash effects.
Clay L.
'67 Sprite
At 07:36 PM 11/20/2001 -0800, Paul A. Asgeirsson wrote:
>If you jack up just one wheel to count the driveshaft revs, then you need
>to do
>two revs of the wheel. Then the driveshaft revs equal the dif
>ratio. (1.95 X 2
>= 3.9!)
>
>There are also numbers stamped on the top of the dif carrier, just to one
>side of
>center there is a boss that has the numbers stamped on it. Might need a wire
>brush and a mirror. You might also check out the tachometer for being off
>some.
>
>Have some fun, find out the distance one rev of the rear wheel travels,
>know the
>dif ratio, and a measured mile and you can calculate the RPMs.
>
>Paul A
>
>Brent Wolf wrote:
>
> > While I was under the 76 playing with the brake hose, I got to thinking (I
> > know - shouldn't do that) about the final drive. Why are my rpm's so high
> > at 50 mph (about 3400). If my final drive is 17.3 mph per 1000, then I
> > should be flying down the road at almost 60 (58.8). Anyway. I was also
> > told it sounds like a 4.22 diff is installed (about 15 per 1000) So I
> looked
> > up an old driveline info section and was read - To determine final drive
> > ratio, raise one wheel, mark driveshaft, mark wheel, rotate wheel one (1)
> > revolution and count driveshaft revs. (3.9 = 3.9, 3.7 = 3.7, 4.2 = 4.22).
> > Ok easy enough.
> >
> > There must be something wrong or I can't follow instrucitons. My drive
> shaft
> > rotated exactly 1.95 revs (not quite 2 and more than 1.9) per wheel
> > rotation. What am I doing wrong? Is there anyway short of pulling apart
> > the diff to determine what is inside?
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