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Changing ratio on a 47 Rear End

Guest Wes

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I saw this posted on this WEB site about a 47 Packard for sale and was wondering if anyone else has tried this and where can you get the parts to do this?

"Legendary NorCal vintage car mechanic Wayne Ballerstein, who worked in the Oakland, CA Packard dealership in the late '40s rebuilt the 3.92:1 differential which we substituted for the factory 4.09. This was often done at Packard, Hudson, etc. dealerships in the day for drivers who enjoyed frequent fast long-distance business trips over the increasingly better roads after the war."

I'm still working on rebuilding mine and this looks like the better way to go.


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Have you sat down and calculated how much this change will lower your engine RPM at a given speed, say 60 mph? The arithmetic is pretty basic grade-school stuff and I went thru it looking at possibilities for my 34 Eight. I'd guess without doing the numbers that going from a 4.09 to a 3.92 is probably only going to make a difference of about 150-200 rpm. I suppose every little bit helps and finding an installing a factory-correct overdrive is a lot of work, but the reward will be significantly greater.

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