Rear Diff *&(()%!!!

ranger952 · February 14, 2004

You all are going to love this........

I posted a question last night about changing my rear diff fluid. I had changed it a couple of weeks ago, and last night heard a thump from the rear end. I thought I had not gotten all of the friction stabalizer in there...well....NOT THE PROBLEM!!!!

Turns out that the small bolt holding my rear diif "pin" in place (the big pin that holds the whole assembly together), had come loose, releasing the pin. The pin shifted forward almost exactly halfway out of my diff, and sheared off, leaving the bolt and half the pin laying in the bottom, stuck to the magnet.

I kept driving, not knowing this. Made it home, made it to work, made it to my buddy's garage today. About 100 miles. How?

The other half of the pin, when sheared off, mushroomed at the top, and spread out, not moving any farther. It kept everything together until I took off the cover thinking I was doing a fluid change. With a VERY little amount of pressure, it came out. One good bump and I would have been toast.

Of course, I cant get the part until morning. The new pin is about $10 total. So, this pin saved me from 2-3 thousand in damage easy.

Moral? Yes, there is one. PLEASE check this tiny bolt that holds your pin in when servicing your rear diff.

My buddy, who is a mechanic, 30 years worth, said that the only ending to this that he has ever heard of is the pin moves, stops the diff, and everything starts blowing apart.

I have the pin still. Anyone want to see pics? :-)

Lucky, lucky, lucky!!!!

Jayman, you forgot to tell me to check this bolt while changing the fluid. I am really just kidding. I have never heard of that. Well, I have now!!!!! The hard way.

100R1 · February 14, 2004

If I read your post correct, you had the rear diff. serviced several weeks before the rear failure.

Did the shop that serviced the axle remove the cover?

If they did I would suspect that the person whos serviced it loosened the lock bolt on the pinion mate shaft.

OR

the factory did not torque it properly

OR

there was no thread locker (again a factory oversite)

Not sure of the correct torque specifications for your rear axle, But I have done dana 35 & chrysler 8-1/4 & they usually are torqued to 12 -15 ft lbs of torque.

Good thing you caught it when you did otherwise $$$$$$$$$$$

ranger952 · February 14, 2004

I serviced it myself a couple of weekends ago. I didnt check the bolt. I didnt know too.

It didnt look like any locker was on the bolt.

What gets me, is that this is such a simple thing to check. I really wonder how long that darn thing was loose??? Could have been a long time.

willfxp · February 14, 2004

Not sure what pin you are referring to. I changed out my rear diff fluids a few weeks ago, so I'm a bit curious. Thanks!

JayMan · February 14, 2004

Jayman, you forgot to tell me to check this bolt while changing the fluid. I am really just kidding. I have never heard of that. Well, I have now!!!!! The hard way.

GEEZ are you KIDDING?

No, I guess not.

Cripes, I have NEVER heard of a pinion lock bolt loosening like that! EVER.

I know I've never checked them, but after your little misadventure, you can BET I'll start that procedure! One more potential disaster to keep me up at night biting my nails!

I've built a few differentials and have ALWAYS put a dab of LockTite on the lockbolt threads before torqueing it in. Most service manuals recommend that to prevent JUST what you described.

Geez, must be a Chevy. If that had happened to a Furd or a Dog, the pinion shaft would have jammed against the housing, the carrier would have INSTANTLY stopped turning (BTW locking up both rear wheels at highway speeds), the pinion shaft would most likely have sheared right off, and possibly the driveshaft would have come apart too and whacked the plastic gas tank.

This DOES sound suspicious. I don't see how the pinion shaft lockbolt could have just loosened up like that. If it had been loose from the factory, that would have happened within the first few thousand miles. Hmmmm.

I hope nothing got shifted around too much. That is, I hope your backlash is ok.

Considering the more likely outcome (Thousands and thousands in damage) I guess you had a happy ending.

redvett · February 14, 2004

I have had 3 of them loosen up in 38 years and many miles. I dont think brands make a difference either. Remember that the GM axle is made by American axle and Fxxd & Dxxxe use the same company to make their axles. Some of those bolts just work them self loose. Seems like snowplowing seems to make it happen more often.

ranger952 · February 15, 2004

Well, I got the new pin in. It was 6.50, plus 3.00 for the new gasket and 16.00 for new fluid. No comparison to 4-5 thousand in potential damages.

In looking at this thing over and over, I just cant beleive how lucky I was. Please everyone, check the bolt that holds this pin in. When I rechange the fluid in a month or so, I wll take pics to show you that dont know what I am talking about. I would have done it today, but dont have my digital camera. (My brother had a new baby Wens, and I gave it to him. I know priorities. Should have kept it for the truck!! :-))

Anyway, if you really dont know what I am talking about with this pin, PLEASE ask someone who does know. JayMan has been a big help to me on this site. He may know.

If someone who IS changing their diff fluid in the next couple of weeks and has a digital camera can post one or two pics showing the bolt and pin, that would probably help those who dont know.

ranger952 · February 15, 2004

Geez, must be a Chevy. If that had happened to a Furd or a Dog, the pinion shaft would have jammed against the housing, the carrier would have INSTANTLY stopped turning (BTW locking up both rear wheels at highway speeds), the pinion shaft would most likely have sheared right off, and possibly the driveshaft would have come apart too and whacked the plastic gas tank.

From what I understand Jayman, this is what SHOULD have happened to me. Luckily the magnet caught the bolt that came out and the pin sheared with half staying in to hold the diff together. One in a million!

100R1 · February 15, 2004

I hope you FLUSHED the hell out of not only the carrier but also the housing.

As the metal shavings will work their way into the various bearings and could cause pre-mature failure.

I see you are going to change the fluid again in a month or so. I would make it sooner than later if you did not flush the whole rear axle. Metal shavings can migrate all the way to the wheel bearings almost as easily as to the carrier & pinion bearings.

And this happened on friday the 13th ?

I hope you played some lottery numbers that day!

JayMan · February 15, 2004

Good point on the axle flush. Hopefully the magnet in the cover will catch most of the particles. Otherwise just a fill and drain won't be able to suspend and flush most of the particles.

Yeah, imagine if he had played the lottery the same day. We could have bragging rights to knowing the next PowerBall winner!

ranger952 · February 15, 2004

I flushed the whole assembly pretty good with gear oil. Also, we did have to fish around with some of those antenna type magnets to pull some of the mor stubborn parts out from under the pinion gear. Seems all of the particles fell to the bottom or stuck to the top.

I think just driving under 40 mph from when it happened to when I pulled the cover helped with that, plus the fact that I had just changed the gear oil helped with the magnet and fluid collecting everything.

If I did win powerball guys, I hate to say it, but I probably wouldnt have to come here anymore. I could pay someone to!

JayMan · February 15, 2004

Sounds like you flushed things out very good. Unless the seals were damaged by the particles, everything should be fine.

Yeah, if you win the PowerBall, the LAST thing you'd have to worry about is babysitting a vehicle.

chvythndr · May 14, 2004

I'll get some pics in a few weeks. I'm regearing a buddies truck to 4.56s. I've never heard of the cross-pin coming loose before. My guess is it loosened up due to not being tightened to factory specs when the carrier was originally installed. The 5/16" screw that holds the cross-pin in place must have come loose.