qtlow

This winter I'm taking time to go through my rear suspension and differential to address some side yoke slop and while I'm at it, wheel bearing and control arm bushing inspection/maintenance.

Here's an interesting little discovery I made after removing the differential cover. One of the ring gear bolts never got torqued tight. But never backed out either luckily.






Upon removal of the bolt my only conclusion is the threaded hole in the ring gear must've had a burr or trash in it during assembly which caused a false torque reading that went unnoticed.




Now, I can't say for certain that it came from the factory like this and has just been hanging in there for the last 47 years. But knowing the history of my car, I have no reason to believe anyone has ever been in there before. Still has the GM gears with the 3.55:1 ratio matching the "CAN" axle code and dated correctly prior to the build date of my car.




My plan is to chase the bolt threads, run a bottoming tap into the ring gear and re torque using some loctite. Probably wouldn't hurt to re torque the rest of them too.

Gordonm

The threads left on that bolt look pretty bad. I would spring for a new set of ring gear bolts and replace them all. Retorque all of them with some Loctite. Cheap insurance against failure.

MelWff

the same thing happened on my original 69 3.55 rear but in my case I found out one or more bolts had loosened to the point of falling out and projecting themselves through the rear cover at speed.

PainfullySlow

Agreed and those bad threads was the first thing that I noticed. I would chase those threads with a tap before installing a new bolt.

qtlow

Thanks for the replies. The bolt really isn't that bad. The camera flash makes it look worse than it is. It's only the first 2 threads that are damaged which was why I was going to chase it and re use it. But like Gordonm said, cheap insurance to replace and re torque them all using loctite. I guess that would be the smart thing to do. I am thankful I caught it now before something bad happened.

Priya

By fopaux did you mean faux pas?

TimAT

IF you upgrade to ARP bolts, make sure you chamfer the bolt holes in the carrier.

qtlow

Yes, will do thanks. I recently read a thread about this.
Before I pull the trigger on new ARP bolts I'm going to dig through my bolt collection. I might actually have a factory GM ring gear bolt or two.

carriljc

I thought about sending a P.M.....You coulda sent a P.M....

GTR1999

Common enough issue. If you are not going to pull the posi case then you can clean and blow out the holes using acetone or brake cleaner. Dry fit the bolt to make sure there is no thread damage in the RG hole, then use some Loctite #271 on it and torque it to 69 ft/lb. Do all the others. The best option is to use the ARP bolts, in an emergency you can use the grade 8 bolts that come in the kits- but why really, they are not as good as originals or ARP's.

68/BB

I wouldn't be concerned about that bolt myself. The wear looks to be on the crest and that really shouldn't be a problem since the pitch diameter does not appear to be affected. JMO

qtlow

This was my initial thought too. I chased the threads this morning just to see how bad it was. I used a thread chasing die, not a thread cutting die because I didn't want to cut new threads in it.

It's really no surprise that I literally ran it all the way down with my fingers with only very slight binding at the start of the thread. I followed that with running a 3/8-24 nut on it and it spins right on.

Like I mentioned in my previous post, I'm going to look in my bolt collection for a good factory ring gear bolt. If I can't find one, I think I'll just run this one after chasing the threads of the ring gear and dry fitting the bolt like GTR said. And follow that up with cleaning, loctite, and re torquing the rest of them.

Thanks for all the replies, even the spelling police.
Priya, I'll contact a mod to see if they can fix my spelling faux pas in the title.