On the .com forum I'm getting questionable answers to this one.

My '74 Scamp has a 7.25 rear. 9 bolts and small. I jack it up and count revolutions. Here's what I got. Both wheels off the ground BTW. 1 wheel revolution gives about 1.3 driveshaft revolutions. Someone on the other forum says it's a 2.76, which sort of makes sense. He says with one wheel on the ground you have to double the revolutions. Can anyone explain what's going on here? Is there some strange interaction with the planetary gears or what?

I thought there would be a straight ratio. But not the case. I did the same test on my Chevy Caprice and got similar results.

Thanks.

Hmm, with both wheels on the ground, and the trans in neutral, turn the driveshaft by hand. Count how many times the driveshaft has to be turned for one full wheel revolution. That is your ratio. Both wheels should be turning at the same rate but in the opposite direction assuming an open differential.

Check this post out for pix of where to find the ratio stamped on the 7 1/4" housings.

http://www.slantsix.org/forum/viewtopic ... atio#27473

Also, if you have the back cover off (assuming ist not an 8 3/4) to change the fluid, you can check whats stamped on the ring gear. there should be a fraction such as 43/12, for example, or a decimal figure, 3.23 for example, stamped into the ring gear near the part number stamping. If it is a fraction, just devide one into the other, that will give you the ratio. If its a decimal figure stamped in, no math required, thats your ratio.

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"That thing gotta HEMI in it??"

Pierre,
We should warn textoad that if he does this he better not get under the car to turn the driveshaft, or he'll run himself over.

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There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.