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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