Guest Posted December 23, 2001 Share Posted December 23, 2001 I have a 70 Olds 442 W-30, 455 worked nicely. 400 tranny. 12 bolt rear; only one tire spins. Original rear from 70 Cutlass 455. I know nothing abut rear-ends. I want to change my gear to a 3.90 (maybe); daily driver- so I like the idea of limited slip. Can someone teach the ins and outs of a rear and my options. TIA Link to comment Share on other sites More sharing options...
Guest Posted December 26, 2001 Share Posted December 26, 2001 The rule of thumb is that 3.55 gears are the numerically highest you should go on a street car. Even then, if you do a lot of freeway driving then you may want something numerically lower. A good compromise would be 3.23 or 3.31 gears. The absolute best setup would be to run an overdrive transmission with a 3.73-4.10 rear end. This gives you acceleration and low crusing RPM.<P>To calculate what gear ratio you have right now jack the rear of the car up and put a chalk mark on the driveshaft and one on the tire. Turn the wheel one revolution and count how many times the driveshaft turns around. For instance if it turns about 3 and 1/4 times for every tire revolution then your rear-end ratio would likely be 3.23. Link to comment Share on other sites More sharing options...
Guest Posted December 26, 2001 Share Posted December 26, 2001 I recently went through the same ordeal of trying to identify and investigate options for an Olds 12 bolt I acquired. A great website with a wealth of information is <A HREF="http://www.442.com" TARGET=_blank>www.442.com</A> The frequently asked questions section has a great deal of useful information on differentials as a whole and gives some useful information on the Olds 12 bolt. Good luck. <BR>Kevin. Link to comment Share on other sites More sharing options...
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