Ubolt tightness and sheared center pins

Hey everyone,

Just went through a miserable experience late last night and this morning...thought I would impart some wisdom so a potential problem can hopefully be avoided by others. I had been driving the past month or so with ubolts that were only "partially tightened". What I didn't think about while I was doing this was how much stress is put on leaf spring center pins when the axle rotates even 1/100 of an inch during every brake and acceleration. Last night my axle actually went back to the point of touching my rear quarter panels in the wheel well and I got lucky I didn't shred a tire or loose control of my Jeep. The point of the story is, learn from my idiotic mistake, and if you have ubolts that have just barely enough thread to tighten down...add more threads or get different ubolts, it's not worth a safety risk chancing it. Hope this helps someone in the future.

-Collin

yes that should be common sense to use proper torque on all critical parts, especially parts that hold your whole rear end to the chassis.

stevedrums said:

yes that should be common sense to use proper torque on all critical parts, especially parts that hold your whole rear end to the chassis.

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Should be but all I'm saying is sometimes common sense can get the better of you. I didnt figure the little bit of torque I was lacking would be a big deal, turns out it really was though.

BIGSLVRXJ said:

Should be but all I'm saying is sometimes common sense can get the better of you. I didnt figure the little bit of torque I was lacking would be a big deal, turns out it really was though.

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Live and learn. Even the most experienced wrenchers make some dumb mistakes sometimes. Glad nobody got hurt Collin!

Yep, you got to "live and learn", but it could have gone the other way.

Of note, there have been a number of posts that the u-bolt mounting plates will bend on you when torquing the u-bolts.

Made mine out of 1/2" steel plate. I don't think I'm strong enough to torque the bolts down that much :roflmao:

Glad no one got hurt, and you learned the lesson without too much damage to the XJ it seems...

No real damage done to the XJ or myself thankfully. I felt like an idiot for posting this and knew I would take some crap for it but...I figure even if it helps only one person down the line, it was still worth while.

kastein said:

Made mine out of 1/2" steel plate. I don't think I'm strong enough to torque the bolts down that much :roflmao:

Glad no one got hurt, and you learned the lesson without too much damage to the XJ it seems...

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1/2" plate? Did you ever work in a Soviet tractor factory? :scared:

Actually, that is impressive!

kastein said:

Made mine out of 1/2" steel plate. I don't think I'm strong enough to torque the bolts down that much :roflmao:

Glad no one got hurt, and you learned the lesson without too much damage to the XJ it seems...

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Actually, there is a torque specs for the 'U' bolts. I use a good quality (grade 10 I think) after market 1/2" 'U' bolt that is rather springy tightned to 65 ft lbs and never had a problem. I wonder if bending the plates is caused by over tightning or a weak/defective plate.

BIGSLVRXJ said:

No real damage done to the XJ or myself thankfully. I felt like an idiot for posting this and knew I would take some crap for it but...I figure even if it helps only one person down the line, it was still worth while.

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Been there, done that. Last week I overdiagnosed a problem, XJ just sputtered out and stopped running... voltmeter was at 9V and I was 60 miles from where I usually run out of gas so I figured it was the alternator and went and bought a new one. Just before installing it (luckily) I said what the hell, I'll try putting gas in the tank. Guess what it was? Yep, I ran out of gas 60 miles early because I went from bald 32s to new 33s, blew my transmission, and limped it home 25 miles in 1st gear at 4000rpm. Now the autismzone guys laugh at me, that makes me feel pretty speshul :dunce:

joe_peters said:

1/2" plate? Did you ever work in a Soviet tractor factory? :scared:

Actually, that is impressive!

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Nope, but I looked at the prices on the JKS U-bolt plates, said "holy crap! they sure are proud of those" and bought 3.5 feet of 10" wide 1/2" plate for just under 2/3 the cost... sold the leftover plate off and got about half my money back. Even including the drill bit I had to buy (I didn't have a good 9/16" drill yet) and the cutoff wheels I came out spending approx. $45 on the pair, vs $92 for the JKS ones...

techno1154 said:

Actually, there is a torque specs for the 'U' bolts. I use a good quality (grade 10 I think) after market 1/2" 'U' bolt that is rather springy tightned to 65 ft lbs and never had a problem. I wonder if bending the plates is caused by over tightning or a weak/defective plate.

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Probably ISO Property Class 10.9 (the standard used for metric bolts, roughly equivalent to a grade 8 - I don't think a grade 10 actually exists in the ANSI spec. I think bending the plates is caused by both... the stock plates aren't all that thick (3/16" or so I think?) with a fold at the leading/trailing edges to help with rigidity, but they still seem like something I could bend fairly easily.