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Old 01-25-2011, 09:14 PM
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Quote:
Originally Posted by tomslik
well, theres a casting # that'll end in 789 if it's the good one.
make sure it's a posi or be prepared to spend $$$
just about any 8 3/4"er is decent though...

i'm a chevy guy (and rambler)too, so i've been getting eddycated....
That would be a 489 case or a 741 or 742. differences are pinion sizes and way you adjust pinion preload.

741 case uses a 1 3/8 diameter pinion and shims to adjust pinion depth/preload
742 case uses a 1 3/4 diameter pinion and shims to adjust pinion depth/preload
489 case uses a 1 7/8 tapered pinion, shims and crush sleeve for depth/preload

489 is considered the strongest but the "use once" crush sleeve is a pain.
All carriers can use either cone or rebuildable clutch type Sure-Grip units.
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Old 01-25-2011, 09:23 PM
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pishta,

welcome to Hotrodders.com

I split out your information from the old thread you posted to.

thanks for the information
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Old 01-26-2011, 03:19 AM
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Quote:
Originally Posted by pishta
That would be a 489 case or a 741 or 742. differences are pinion sizes and way you adjust pinion preload.

741 case uses a 1 3/8 diameter pinion and shims to adjust pinion depth/preload
742 case uses a 1 3/4 diameter pinion and shims to adjust pinion depth/preload
489 case uses a 1 7/8 tapered pinion, shims and crush sleeve for depth/preload

489 is considered the strongest but the "use once" crush sleeve is a pain.
All carriers can use either cone or rebuildable clutch type Sure-Grip units.

yep, you're right...don't know where the "789" came from, musta been early in the morning...

489 and 742's have a better aftermarket following, virtually nothing for the 741's
489's have a stronger pinion, 742's have stronger carrier bearing caps ( the stock/ss guys tell me...)
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Old 01-26-2011, 04:38 AM
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thanks for the clarification tomslik.

sometimes age affects folks as they type.
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Old 01-26-2011, 05:18 AM
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Originally Posted by Crosley
thanks for the clarification tomslik.

sometimes age affects folks as they type.

..if you want to call what I do "typing"
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Old 01-26-2011, 10:53 AM
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I haven't done a lot of 8 3/4 rear ends, but someone that I talked to prefered the 742 case. I think it was Tom at Tom's Differentials. I didn't ask why, but it might have been because of the bearing caps. Here is what happened to a 489 case that I built for a drag racer.

We put a steel cap on it and never had another problem with it.
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Old 01-26-2011, 06:21 PM
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Quote:
Originally Posted by tomslik
..if you want to call what I do "typing"

I thought the court ordered medication had helped you.
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