Expert: Brad Sears - 2/5/2010

Question
I have a 1950 Chev Bel Air 2 door hdtp. It has a 1960 235 engine. I have been told that to get good highway speed I should put in a 1949 - 1954 Automatic rear end (355).  Without knowing better I bought a 1953 Chevy rear end.  I didn't know if it was auto or standard (it had been torn apart).  So I guess I have a 370 rear end.  Will that work as good (highway) as a 355 rear end?  Thank You.
Wayne

Answer
I did a bunch of research on this question and here is what I found. The 1953 Chevrolet used the same 4.11:1 rear axle gear ratio as standard equipment as the 1950 series car did. There was a 3.77:1 option in 1953 that I believe was used in the automatic Powerglide cars. The standard transmission cars used the 216 CID engine while the Powerglide used the more powerful 235. Now consider that the lower numerical gear ratio will lower the engine revolutions at highway speed in top gear but will also reduce the power to the wheels. If you live in a hilly area it may mean more down shifting to climb hills but it will also mean slower acceleration in the lower speed ranges. In stock form this engine car combination should be able to keep up with 65 mile per hour traffic without a problem since the 235 engine has full pressure lubrication and hydraulic valve lifters. I would however caution that the brakes, suspension, and bias ply tires are more of a limiting factor for high speed driving than the rear axle ratio. I wouold be comfortable if the car is stock at 55 miles per hour.
Brad