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High Speed rear end gears


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I appreciate everyone's help so far. Whatever gears the car has (1940 80 series convertible sedan) it is spinning too fast at 50 mph. I just restored the engine (car was originally restored around a 60k original engine) and the last thing that I need to do is strain the new engine. I do like to tour with my cars (Caravans, etc) so would like get it to run comfortably at freeway speeds. Price is not a major consideration. Thanks for the help and questions.

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Keep after it for the sake of those that follow.

I'm in the same position that you are but with a '40 series 90.

I've just begun my quest for a taller rear gear too, and the big series cars are different in many ways.

As a last resort you could consider converting over to an open drive line, which opens up a lot of Buick and other GM models rear ends. Nobody would know if you don't place mirrors under your car at the shows.

Mike in Colorado

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The ring & pinion part number is used for only 1940 S80, 1941 S90 & 1942 S90 (up to frame ??) [46:11 ratio 4.182]

ring 5.503 1302177

pinion 5.503 1313200

Axle shaft is common to 1938 1939 1940 series 80 & 90 and 1941 series 90

group 5.420 part 1394560 Shaft, rear axle right

group 5.420 part 1394561 Shaft, rear axle left

In the Torqetube magazine Vol XV Issue 6 ( www.1937and1938Buicks.com ) is an article where a person with a 1937 Limited (S90) replaced the diff with 1955 assembly, third member & torque tube (ratio 3.4:1)

Edited by 1939_buick (see edit history)
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