You could consider this a poll: I notice that the 3.23 ratio is popular. Before I get off my lazy duff and screw a new rear together, any concerns with an automatic, no overdrive in a vehicle that sees highway duty? All answers will effect my decision.

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Troops on the battlefield have a far better view of the battle then the generals who lead them

In my 71 duster with 3.23 rear and a 904, I run about 3k on the highway at about 70ish give or take depending on the grade.

I deffinately wouldn't use a numerically higher ratio for a daily driver, but a 3.23 is a good comprimise. My engine is all stock internals except for a 30 over bore and it still has a bit of pull left on the highway with those gears.

Post a tire diameter and I will list rpm vs speed for several different ratios for comparison.

Even better, send me an IM with your email address and I will email you the Excel program I made to do these calculations for me.

-S/6

For a frequently street driven car, I'd say 3.23 is a very nice ratio. You can cruise all day at 3600 RPM if you want, although it may be loud. 3000 RPM is a good cruising speed, as Pierre said. If you don't want OD, but want some off-the-line performance, then 3.23 is a VG choice. I ran a 3.23 for years with a stock 904 auto, and would cruise as fast as 75-80 MPH. Gas mileage really doesn't change much either, if your motor's tuned for that rpm range.

Lou

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Home of Slant6-powered fun machines since 1988

Out West we have more distance to cover and some long open highways. For a car that I want to drive at 75-80 MPH I use the 2.94 ratio.
The 2.94 is not as spunky off the line but it sure likes the high speeds.
DD

I use a 3.23 ratio with 24" tires in my Valiant and my Roadmaster. They both have OD transmissions. I live in the land of no stoplights or speed limits. Frankly I could not live with 3.23 with no OD. The engine RPMs would be so high at 75 the noise would drive me nuts. My car came as a 3spd manual with 3,23 ratio. The ratio was a big factor in me choosing a 5 speed OD. (2300 rpm AT 83 MPH)
If you live in the city and never go over 60mph the 3.23 is very nice with 24" tires. If you still have small 13" tires you will go nuts.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

I am also running a 3.23SG 8.75. I am running 235/60R14(25"tall) tires in the rear. at 70mph I'm turning 3000rpm and will pull to 90mph (4000rpm) easily. it is quite loud though(headers 2.5"pipes turbo muffler) I have seen at least a 2 mpg decrease going from the 2.76's

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