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3.91 SF Rear End

Old February 19th, 2019, 10:10 AM
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3.91 SF Rear End

How rare is this rear end?
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Old February 19th, 2019, 10:39 AM
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P,
SF was for 1970 3:23 Anti-Spin. I would think a pretty desirable gearing, not too high or low. My 70 Pace car had an SF and drove nice around town and highway.
According to my books 3:91 for 70 would be code TO for W-30 which I think is pretty rare along with TM (3:42) for W-30. I also see there are codes SH and SJ for 3:42 and 3:91 respectively for non W-30. Not sure the difference but a 3:42 and 3:91 and higher were considered performance axles and I would think maybe a bit more HD?
I think the SF 3:23 would be hard to find if needed?
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Old February 19th, 2019, 11:33 AM
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I believe TO and TM were also used for the W31 in 1970 as well. It's been quite a few years, but if memory serves the 70 W31 I had came with the TO rear end.
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Old February 19th, 2019, 12:06 PM
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Wrong Code - it's a SJ

had a brain fart....it's an SJ rear end.
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Old February 19th, 2019, 06:24 PM
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I don't know whether this is accurate, but

https://tech.classicoldsmobile.com/73.shtml
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Old February 19th, 2019, 07:03 PM
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SJ is the code for 3:91 anti spin non W car. I would think this is somewhat rare, but not as valuable as the TO coded 3:91 W rear.
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Old February 20th, 2019, 11:55 AM
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Is the TO 3.91 only available on the w 30 or a w 31 cars?Could it be ordered on a plain Cutlass?
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Old February 20th, 2019, 12:47 PM
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I believe TO and TM rear ends in 70 were W car only.
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Old February 21st, 2019, 06:38 PM
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there are 3.91 geared rallye's, so those would get the SJ code
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Old February 22nd, 2019, 09:06 AM
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