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Troy
12-31-2018, 10:52 AM
Hey All,

I have a few questions regarding the differential in my '55.

1. When I was going to school in Arizona I blew up third member in my '55, my boss found me another that I believe came out of a '63 Impala. My question is... would the ring and pinion that fits the '55 third member fit the '63 third member?

2. What's kind of a good all around gear ratio to use? I have a relatively stock 350, Turbo 400, my tires are 25" OD now and they may be 26"ish when I put new ones on. Future plans may be a 4 spd OD Automatic.

Thanks for your help!!!

markm
12-31-2018, 11:29 AM
I believe 55 &56 gears are different than 57-64. However a complete later jug can be swapped in as you did. With a th350 a 3.08 gear from a 59-64 works well. With an OD 3.36 or 3.55 are good.

Troy
01-01-2019, 01:48 PM
Thanks Mark I'll look into that difference.

Rick_L
01-01-2019, 02:08 PM
The 55-56 gears as well as the differential carriers were different from 57 up. The gears were thinner and the carrier was different to compensate. As said the entire 3rd member assembly is interchangeable.

If there was trouble way back when, most guys just went to the wrecking yard and got another 3rd member. Easier, faster, and cheaper than repairing the 3rd member with new gears. The only exception to that was broken spider gears, you could easily replace them if the broken ones didn't tear too much up.

Troy
01-05-2019, 10:59 AM
Yeah Rick, that was it. I was a poor student at the time so $50 was the only way I could go. When it broke it blew a quarter sized hole in the casting so no repairing.