#1  
Old 09-18-2020, 08:24 AM
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Default Wear on differential cross pin shaft

a guy in our local club had growling noise in his Firebird 10 bolt. Pulled apart and there was extensive wear on the shaft where the spider gears ride. It is an open diff. Any idea of root cause? Shaft too soft?

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Old 09-18-2020, 08:34 AM
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Common to see when i was a teen-30's. No so common now. Think it shows the spread of rear quality varied in production.

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Old 09-18-2020, 09:38 AM
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Too many one tire fires. gets the spider spinning too fast and burns up. Seen it wipe out the case ( Or Carrier) as well.

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Old 09-18-2020, 11:35 AM
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Quote:
Originally Posted by Lemans64 View Post
Too many one tire fires. gets the spider spinning too fast and burns up. Seen it wipe out the case ( Or Carrier) as well.

I had a set of loose spider gears and worn/galled pin in the last rear I rebuilt. I also figured this was due to too many violent one wheel peel burnouts like Lemans64 surmised. Everything else was in good shape except those pieces.

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Old 09-18-2020, 11:37 AM
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Yup one wheel burnouts, think what happens in the differential when one wheel turns slower / faster than the other one

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Old 09-18-2020, 11:53 AM
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Replace the pin and both spider gears and cross bolt and run synthetic fluid, issue solved!

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Old 09-18-2020, 07:31 PM
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Now he has an excuse to put a posi carrier in there.

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Old 09-19-2020, 05:32 AM
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Yup, that would be the way I would go if I had the funds!

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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!
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Old 09-19-2020, 09:42 AM
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Something else to watch out for with those cross pins is how they fit in the carrier. If there is any play or wear in the carrier and that cross pin moves around a bit, it will snap that tiny cross pin bolt.

I've had a couple of them do that on OEM carriers. Take that little bolt out and only the threaded part comes out, the rest of the pin snapped off and stays in there. You then have to drill that cross pin and it's a hardened shaft, not easy to do. I've never really seen a cross pin that was so worn it needed replaced, they are extremely hardened steel. But it will eat into that iron case like butter if the fit is sloppy.

So when this happens, and that cross pin no longer fits snug, it's time for a new carrier anyway.

Just an FYI

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Old 09-20-2020, 06:42 PM
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Pictures of shaft
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Old 09-20-2020, 10:41 PM
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Wow, I probably can't tell you how hard that shaft is, to see wear on it like that is really doing something. I've drilled my fair share of those pins to get them out when the little bolt is snapped, and those things are TOUGH!!

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