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Daaaaaamn ! !
 

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It was in this one
I am curious as to what was going on when it happened. The cracks look like they are from reverse engagement as the appear to be cracking with the pinion yoke going "up" . In forward gears the pinion yoke is loaded downward and the "gear" portion tries to "climb" the ring gear. That is a rare failure especially for an 8" with it's lower pinion angle.
Randy
 

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Discussion Starter · #13 ·
I am curious as to what was going on when it happened. The cracks look like they are from reverse engagement as the appear to be cracking with the pinion yoke going "up" . In forward gears the pinion yoke is loaded downward and the "gear" portion tries to "climb" the ring gear. That is a rare failure especially for an 8" with it's lower pinion angle.
Randy
Hey Randy, all i did was put my foot down in first, changed into second and pop.....i have made a 9" for it now so all good.
 

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My guess of a cause would be a bad suspension that let the rear wheels jump on hard take off's. That or revving high before dropping the clutch are axle killers. Rear axles are rarely killed by pure engine power. It's also an early weak 8 inch, 67- got cases with more ribbing to ad strenght.
 

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Back when I bought my 65 it also got a broken stock rear. The pinion had killed it's bearings and broken the case inside. The guy that sold the car had done that with a completely stock 2-barrel 289" and very little traction. The car is now powered by a hot 347", have better suspension, much more traction and the new 8 inch have no problems handling that.
 

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Hey Randy, all i did was put my foot down in first, changed into second and pop.....i have made a 9" for it now so all good.
It may have been hanging on by a thread for previous abuse. FEW of us check cases for cracks when we rebuild them. I have dis assembled "running" 8 and 9" differentials and had the main cap be in two pieces. Yours is a new one on me without "obvious" drag strip abuse when it happened. The '67 up cases are certainly stronger than that early one.
Randy
 

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Yeah, wheel hop is a killer, whether in a car or offroad truck with large tires !
Yeah, everything inside are hit HARD by the repeating on-off traction and if the car got leaf springs, then the pinion angle will probably be all over the place. It may stand that abuse for some time, but in the end something are going to break. The problem gets even bigger if the axle are worn and not new and tight.
 
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