Elexwiz

So I get home today, open the garage door, and this is what I find:



This is the upper bolt for the shackle. I put installed these on Tuesday night. These are 14mm, 10.9 bolts, as evidenced by the head. I torqued them to 109 ft lbs as per my Haynes manual. Is the manual wrong? I'm hoping maybe this was just a bad bolt. But check out the washer. Would a Grade 8 washer imprint like this?



Here's a close-up of the broken bolt head followed by the shackle. This is not going to be fun.

XJ-92

when i did mine i torqued them to 85 ft lbs and havent had an issue since. i couldnt tell you what went wrong here.

Elexwiz

Looking at the close-up of the bolt head, would you guys say that this bolt is steel or aluminum? I got my bolts from a "bolt" store, not the stealership.

Cherockee

It is suppose to be the strength of a grade 8, but it's metric... and probably made in China- therefore the fail bolt. Looks to me like a defect.

Since you just put them in it should be easy to use ... wait for it... an easy-out. And the washer probably doesn't have a grade rating.

Elexwiz

Probably true about China. Looking at the broken bolt head, it REALLY looks like it's aluminum. Steel would have a smooth, somewhat shiny, finish. This is dull and textured. I've already loosened all the other bolts. I will be taking them back and going elsewhere for my hardware.

By the way, I already broke one easy-out. I'm going to ask a friend if he can weld a nut to the broken bolt. It's lathered up pretty good with anti-seize so it should be relatively easy to get out. The reason I can't use an easy-out is that I can't get a drill up there.

edit: China... that's probably what the C H means on the bolt head.... doh!

Moncheche

It's made of old sunken Japanese battleships. Good luck with that.

rrich

It's not aluminum.

Even a cheapie soft washer won't imprint like that. It took a Hell of a lot of pressure to make the imprint before the bolt broke.

You did not have a washer under the nut - - as the suspension cycled the nut/bolt kept getting tighter and tighter - till several hundred lbs of torque broke the head.

The bolt MUST BE ABLE TO rotate with the movement, not get tighter.

Lift the axle till the shackle is in 0 strain, then use a punch to drive out the broken piece.

Check that the other side was done right.

Elexwiz

I appreciate your input but I think you may be confused. This bolt was my the upper bolt on the shackle, the one that goes into the frame. There's only the weld nut on the other end.

The suspension hasn't been cycled at all. I just put these bolts in on Tuesday evening and she's sitting in my garage. She still doesn't have her front axle yet. She hasn't been driven.

Since when does the bolt rotate with the spring? In the case of the upper bolt, if the bolt is rotating then its not tight enough. The weld nut certainly doesn't rotate. In the case of the lower shackle bolt, the spring eye will rotate on the bolt. The the entire bolt is rotating then its not tight enough.

I torqued the bolts to 109 ft lbs IAW the Haynes manual. I checked my torque wrench to make sure I didn't screw something up with the dial, it was good. I did some more digging last night and found a vast range of torque specs for the bolts; from 80 - 110. Even at 80 ft lbs, the bolt would not be able to rotate.

I still question if that bolt is really steel...

gpeade

I'm gonna take a guess here that either that washer is aluminum or the softest steel allowed to still be called steel. If thats a steel washer then it took well over 109ftlbs to imprint it like that. That thing looks like you put it in a press and stamped it with a die.

CCKen

Elexwiz,

I'm not familiar with, nor do I have a parts catalog for a 1987 Cherokee, but starting in 1988 that bolt is OEM P/N 34202118, and is a M14x2.0x120mm, flange head bolt. The same bolt is is called up for the '88-'01 Cherokee. I'd have to check the bolt head on my '99 but I'd bet it's a class 10.9 bolt.

14mm Class 10.9 bolts should be able to handle up to 120 ft/lbs of torque. My '99 XJ FSM calls for 115 ft/lbs of torque on these bolts.

A word about torque values: The torque values in a manual are dry torques, i.e., no lubricant on the bolt threads or under the bolt head. Lubricants will change the applied torque considerably - up to 30% less than the published torque value when lubricants are used. You stated that you used anti-seize on your bolts and applied 109 ft/lbs. I'd say that 80-85 ft/lbs would be adequate with anti-seize on the bolt threads (see XJ-92's post).

Note that the bolt length from the parts catalog is 120mm, if you used a bolt longer than this it may have bottomed out on the other side of the frame rail from the weld nut. If the bolt bottomed out on the frame rail and any applied torque would go out of sight and snap the bolt head. No telling what the actual torque it would take to snap a Class 10.9 bolt.

The dealership should have the proper bolts, in that they were used up until 2001. If the pre-1988 Cherokees used a bolt other than the P/N 34202118, the dealer may, or may not, be able to help you. Most hardware stores may not carry 14mm bolts, especially flanged head, 120mm long, so you may have to get them on line.

When you get this bolt stub out I recommend getting the proper bolts. Even replace the bolt on the other side. Do not apply anti-seize to the bolt threads or under the bolt head.

If you are concerned about that washer being Aluminum, just use a magnet to check it out.

Good luck.

Do you still have the old bolts that were removed so you could match them up to the parts catalg specs?

weebur

If there's one thing the Chinese do really bad it's heat treating steel; it usually comes either too soft or too hard...usually too hard in my experience. I'd just replace the bolt with an SAE grade 8 bolt. 109 ft/lbs won't snap even mild steel of that size.

Elexwiz

Right. I will checking with a magnet when I get home. (why didn't I think of that sooner)

Great information! Thank you. I didn't consider dry torque vs. wet torque. If the torque values change so much then I torqued this to approx 155 lbs. The bolts are the right size, M14 x 2.0 x 120mm. And yes, I planned to replace ALL six bolts in the rear suspension. Thank you again.

Elexwiz

Its not that easy though. The weld nut inside the frame is a 14mm x 2.0 nut.

rrich

If you used aluminum for it - whose fault it that?

What do you think the chances are you bought BOTH a defective bolt AND a soft washer?

Show us a picture of both washer and bolt head sticking to a magnet.

The imprint label on the bolt is NOT aluminum! Even the Chinese aren't that stupid.

Even an aluminum washer won't crush down with an imprint like that.

TRY IT! Put a washer between a bolt head and nut and tighten it gorilla tight. TRY IT WITH STEEL, TRY IT WITH ALUMINUM.

There's something else you aren't telling us. Bolts don't break in the middle of the night untouched for no reason.

It's obviously a phoney post. Next time make up something more believable.

Dan91

Eh, I'd beg to differ. Like the guy a few posts up stated, with lube/antiseize you need to adjust your torque rating accordingly. It's highly likely that a combination of over torque and a bad bolt caused this. Say, for example, the bolt was on the verge of breaking after he torqued it down. Then after some hours of sitting there over-strained it finally broke and let loose. Obviously not something that happens often, but it seems plausible.