Offset and squareness problems of the carrier were common. The fact that it was difficult or impossible to obtain a good pattern may be because of this. Also, 2 new factors were introduced: the new ring and pinion, and the new "posi" unit. If the backface of the ring gear is not flat, or the corresponding mounting surface on the posi cover is not flat, the pattern will wander. Check the ring gear on a very flat surface, use a dial indicator to check the cover.(I'm sure a lot of readers of this thread know this, but we are on page 2 and no one has brought it up yet.)
Looking at the adjuster for the carrier bearings, were the holes for the pin spanner all beat up before? I assume that some one that has done these for 30 years has a pin spanner and uses it and not a puch and hammer to adjust the carrier bearings. Right? It really looks like some one beat the holly shit out of the adjusters. Could it be that once he got the back lash to .008 he over hammered away on the bearing adjusters to get them tight and in the process got the preload on the carrier bearings to tight that they heated up, expanded and broke out of the case??!!!! I can't really tell from your pictures, but do the carrier bearings look like they have been hot? Did you ever check the rear end after you started driving it to see if it might be hot? To have the carrier bearing cap and boss to fail like that really looks like they were both pushing outward from heat. If the bearings were over preloaded and the ring gear carrier got hot, say 300 deg. F, the carrier could expand as much as .030 to .040 inches, doesn't sound like much but when the bearing bosses and caps are already over stressed because the adjusters are over tighten the additional expansion from heat could easily cause this type of failure. Rex
Davy Crockett said it best........."Be sure you're right THEN go ahead". Sometimes it's hard to tell what was wrong from the shelled out pieces. I understand getting the contact wrong; I don't understand how you can generate those kinds of forces on a pinion. The key is in the "hard to get the pattern right" comment. Almost like the pitch circles didn't touch. If it had to be pulled up hard to get the pattern, I think you have a mismatched set of gears.
When all this happen I took him a whole different 3rd member. I just talked to him, he put the "new" one together with the posi carrier, had the same problem with the gear pattern, so he tried again without the posi, not one issue setting it up this time. I did also fail to mention that he said he has never seen main caps on a 9" do that. I've never heard of anybody having a issue like this
Lots of plausible reasons offered as to the cause of the catastrophic failure. The bad pattern seems to have been caused by the ring gear wobbeling due to the posi case being not square to the case (or carrier- whatever you choose to call it). Maybe in an attempt to set the pattern, he did some of the things mentioned in prior posts. The ring gear mounting surface on the posi case can be trued up to save the case.
Who's gears is Speedway selling? Most aftermarket gears suck ass.. Did he use a solid spacer, or a crush sleeve? What was the pinion drag? I have only seen caps fail, in real hi horse power, and sticky tire situations. If the caps got reversed, the spanners were under way to muck offset from the machining of the caps, to the case.I think the carrier was moving side to side, that will be an issue. Or like was stated before, pinion depth, and poor gears, are not right. But that carrier was moving around with way to much backlash.
I'd be checking to see if the axle housing isn't bent. I've seen lots of rearends with with failed bearings where the carrier was sloppy as hell in the case but have never seen one break a cap. I feel that improper setup is an unlikely cause of this failure. I'd bet that your rearend housing is bent which is causing the axle shaft to put excessive sideload on the bearing. this would also explain why the rearend would make noise before and after rebuild, the old bearings were probably just worn enough to allow the misalignment without causing a failure.
Have you removed the pinion nut? I wonder if it wasn't torqued properly. More than a few guys have wondered why only 16 inch pounds or so on the big pinion nut not realizing that's the bearing preload. Couple years back one of the magazines indicated the low inch pounds figure was the proper torque....
No mystery here. I've set up many of these and others, and broke one just about like that. I don't think tooth pattern issues is to blame. I think you simply launched it to hard. Get a nodular case. You can't abuse a standard case in a heavy car. Don't blame the installer, or the vendor.
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