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diff R&P swap question


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Correct me if I am wrong, but I recall that numerically higher diff ratio R&P sets are weaker than the lower ratio R&P's. So a 4.56 R&P would be weaker than a 3.64. This goes back to my 4x4 days. Not sure about the BMW ones.

Frankly, I don't know. I suppose its technically possible based on gear shape. BMW Motorsport offered ring/pinions in increments up to a 6:1 ratio. I'm assuming these were equipped on some alpina and other period cars.

The Alpina book shows these ratios:

All are at 7000 rpm

5-speed C/R trans.

3.45 219 kph

3.64 208 kph

3.9 194 kph

4.1 184 kph

4.37 174 kph

4.75 159 kph

5.32 143 kph

5.86 129 kph

Will scan the graph & post as time permits. Have fun 8^)

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You are going to love that 4.44!

Come out of Oak tree in 2nd and you are in 5th before the top of the hill.

3rd in the start of Hog pan and 5th well before start finish at VIR ending up around 78K into Turn 1.


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3460120 - 74 Verona Touring....... (Sold) sent off to LA.

2760306 - Ultimate driving machine Skidmark 204 car. 72 Inka (Sold)

Formerly the old and slow division of Skidmark Racing. 

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I recall that numerically higher diff ratio R&P sets are weaker than the lower ratio R&P's

This is generically true, I seem to remember, too.

It probably has a lot to do with how 'few' teeth are engaged on the pinion.

(realistically, it's how much of one tooth, what with hypoid gears being what they are, and the pinions having maybe 7-9 teeth)

The 4.27 and 4.44 run noticably hotter than the 3.64 and 3.91, that, I HAVE found.

If you want a laugh, look at the ratings in, say, Machinery's Handbook

for straight bevel gears about the size of the 2002 pinion.

They're in the single- digit HP and max double- digit torque range...

(explains why the spiders give out early, too)


"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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