bolt head came off

[2Farr]

I was driving me 98 12v the other day and herd a loud bang. Stoped the truck and found a hole in the diff cover. Took the truck home and pulled the cover and found this on five bolts. I took carrier out and bearings felt good, ring gear had no nicks on it. Everything looks good except for the five broken bolts. Never seen this happen before. Has any one else have this happen?

 

[Ozymandias]

Factory or Aftermarket?

 

[2Farr]

These were factory. on the truck when I purchased it new. The truck has a auto trans and is a 4 wd. I am putting more torque out than stock.

 

[Ozymandias]

These were factory. on the truck when I purchased it new. The truck has a auto trans and is a 4 wd. I am putting more torque out than stock.

I've never seen something before.
More torque sure adds to it, RAM went from 12 to 16 bolts for the new HO Trucks.

According to the responses here it seems pretty unique.

 

[BigPapa]

Do any of the bolt heads, the broken ones or the ones still holding, show evidence of an impact? I’m wondering if one bolt head broke off and bounced around in there, hitting the other heads and knocking them off. Obviously something like this happened for one of them to knock a hole in the cover.

 

[2Farr]

I'm taking the bolts that didn't break to get them NDT to see if there are cracks under the heads. All new bolts are going back in with lock tight. I have herd of this happening before under high load conditions from other people. Sounds like something that needs to be look at every so often.

 

[SAndreasen]

Under heavy load? What’s a heavy load?

 

[BigPapa]

My experience, I've never seen this happen before from heavy loads or even in high powered trucks with over 1K HP at truck pulls. the force of the pinion on the ring gear is pushing the ring gear into the carrier, not pulling it away. If this is from a "heavy load", the force would shear the bolts off where the ring gear contacts the carrier, not pop the heads off.

It'll be interesting to see what your testing shows on the unbroken bolts. Also waiting to hear if they had evidence of an impact.

 

[2Farr]

Update: Bolts came back. All but one showed signs of cracking under the heads. Rockwell test shows bolts are not grade 8. They were closer to grade 5. Since I purchased the truck new now I get to figure out what happened to these bolts. They are marked as grade 8.

 

[JMcCoy]

Someone (Dodge or Dana/Spicer) likely purchased inferior parts to save a buck.

 

[ironforger]

Itneresting thread. Kind of rare to hear about bolts flying apart inside a differential. Obviously defective bolts. At least you got lucky since the bolt head didn't get stuck in the ring and pinion hypoid gear teeth while you were moving. Edit: I had an old 88 ford E150 van years ago, LSD differential. I was using to tow a junk car out of the mud, one of the tabs broke on the LSD clutch pack, that tab got stuck in the gears while moving and it broke the carrier, not the gears. Fixable (new carrier and clutch pack) but it was expensive.

I'd be curious to know if for example those bolt heads would snap off under the correct torque specs. Can you test that one good bolt you have? Do a destructive test? thread it into a nut and torque it to normal specs, then increase the torque in 10 lb increments to see how much it takes to snap it off. Then compare that to a good new grade 8.

IF im not mistaken, the 98 auto 12v trucks got the dana 70, correct?

 

[Cummins12V98]

"IF im not mistaken, the 98 auto 12v trucks got the dana 70, correct?"

Thats what mine came with.

 

[SnoKing]

Probably over tighten at original assembly.

 

[Cummins12V98]

Probably over tighten at original assembly.

Probably a HarborFreight TQ wrench.

 

[2Farr]

Speaking of Harbor Freight. Drilled holes in head of one of the broken bolts with a drill from Harbor Freight. Yes it is a dana 70

 

[SnoKing]

I have had an old fairly cheap with twist dial in the handle to set the torque wrench. I was getting the tires rotated at Costco in Tri Cities,Wa and they had a test stand in the waiting room, so I went and got my wrench, and in the 100-125 ranges it was spot on. Surprised me!!

 

[SnoKing]

Speaking of Harbor Freight. Drilled holes in head of one of the broken bolts with a drill from Harbor Freight. Yes it is a dana 70 View attachment 119827

Someone sold Dodge some bogus bolts!