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#1 |
Registered User
Join Date: Sep 2007
Location: baltimore md
Posts: 45
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Broken U-bolt Help
I was taking a little trip to the dump today and when I was backing up to the dumpster there was a pop in my front suspension. At first I just thought it was normal sweeks from a 40 year old truck but one of the guys there said theres something hanging down from under my truck. When I looked I saw the passenger side lca damn near touching the ground in the back. The only thing holding up was the shock
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67 c-10 lwb 81 trans-am (in 1000 pieces) 92 firebird (pos) 63 austin heally sprite (future project) 58 chevy pickup (future project) |
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#2 |
Who's got steelies?
![]() Join Date: Feb 2006
Location: Morrison, Oklahoma
Posts: 1,026
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Re: Broken U-bolt Help
Ouch!!! Its an easy fix, but still.... Glad you weren't doing 65 or 70 when that happened.
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#3 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Re: Broken U-bolt Help
Look at the U-bolt real close, you may get to see what it was. Rust could have been a factor, over torqueing upon a rebuild, under torquing, but in all reality, there shouldn't be too many factors in this.
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#4 |
member #16
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Location: Yuba City Ca.
Posts: 3,618
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Re: Broken U-bolt Help
Some model trucks have a larger U bolt, You just have to ream the holes and that should cure the prob. Not sure of what year bit a vendor should know.
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john http://67-72chevytrucks.com/vboard/showgroups.php board vendors ![]() http://www.flickr.com/photos/1745471...7602865984234/ |
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#5 |
Registered User
Join Date: Nov 2003
Location: Alexandria, VA
Posts: 1,534
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Re: Broken U-bolt Help
This has been addressed on the forum before. Not real uncommon. There is a heavy duty replacement u bolt.
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'72 GMC SWB C1500 Custom, frame-off in progress. 383 SBC, 9:1CR, Comp Cams XE262H, Scat internal balanced crank, Eagle SIR 6" rods, Keith Black dish pistons, Dart Iron Eagle 72/180 heads, Weiand Stealth intake, Stewart stage I water pump, Holley 4bbl vac sec, TH350 with B&M Shift Improver Kit. 12 bolt positraction. ![]() ![]() ![]() |
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#6 |
Registered User
Join Date: Mar 2006
Location: Kansas
Posts: 865
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Re: Broken U-bolt Help
with repeated beating from normal use the bolts can crystallize. it most likely started from a very minor flaw in the bolt when it was made. Does the surface that broke look rough? a bit like fine sand? If so that is the answer to why! If it doesn't then look at the way it broke. is part of the broken area dull looking? like it is an old break? If so then it could be over tightening, or over stressed. (hitting a pothole he size of a small car.) Is part of the bolt worn away? if so then it was loose. If it is a crystallized bolt then you might consider changing the other 3. they have been through just as much abuse as the broken one.
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#7 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: Broken U-bolt Help
are those springs cut? and are the shocks the stock ones? if so and the shocks were bottoming out it will cause the ubolt to fail//if not i'd also suspect overtorqueing//proper torque should be right about 45ft/lbs
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#8 |
I am a Referee of life.
Join Date: Jun 2000
Location: Greensboro N.C.
Posts: 13,993
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Re: Broken U-bolt Help
Even though the pic isn't a close up it appears the U-bolt is crystalized.I don't see any rust to speak of but the U-bolt is 40 years old and has probably had it's share of bumps.Just something about the way it broke makes me think it's crystalized.
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The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil" |
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#9 |
Registered User
Join Date: Sep 2007
Location: baltimore md
Posts: 45
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Re: Broken U-bolt Help
Thanks guys. I bought 4 new u bolts from the gm dealer but I have not worked on the truck yet. The front is lowered and I dont know about the shocks. I bought the truck the way it sits minus the front discs. I need to drop the back down about 5" which might take a little stress off of the front end. The thing that really bothers me is that I always heard noises from the front end.even after I replaced all the balljoint and sterring setup when I did the brake swap. Could the lca's be moving inside the U-bolts. I havent looked in to how they mount on these trucks but Im getting ready to find out.
thanks karl
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67 c-10 lwb 81 trans-am (in 1000 pieces) 92 firebird (pos) 63 austin heally sprite (future project) 58 chevy pickup (future project) |
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#10 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: Broken U-bolt Help
easy enough to check those shocks with bottom mounting bolt removed push bottom all the way up into the top then take a marker and mark on the bottom shock body the position of the top shock sleeve then when you have the suspension back together and shock installed you can tell from the mark how much shock travel you have//i'm bettin not much and that there is the cause of your ubolt failure
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71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY |
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#11 |
Firefighter
Join Date: Feb 2001
Location: Yellville, Ar, USA
Posts: 1,943
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Re: Broken U-bolt Help
I've had the exact same problem with my 67 GMC, it's done it 3 times now twice when backing up and turning and the other while going across a small ditch going forward. And every time I had repalced the u-bolts with new ones and torqued them down like they were supposed to be. Now thay make a larger u-bolt 9/16" I think to fix this problem.
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#12 |
Registered User
Join Date: Sep 2007
Location: baltimore md
Posts: 45
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Re: Broken U-bolt Help
Thanks for the replys.
I will look into the shock problem for sure. Does anyone know what year trucks came with the bigger u-bolts or are they strickly aftermarket. Thanks Karl
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67 c-10 lwb 81 trans-am (in 1000 pieces) 92 firebird (pos) 63 austin heally sprite (future project) 58 chevy pickup (future project) |
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#13 |
Registered User
Join Date: Dec 2004
Location: Central Wisconsin
Posts: 1,317
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Re: Broken U-bolt Help
I replaced mine when I dis-assembled the A-frames for paint---they had wore and I didnt like the idea they were 39 years old----new ones were $22 from GM Now Im taking others advice and replacing all the studs for my lug nuts----
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#14 |
Registered User
Join Date: Sep 2007
Location: baltimore md
Posts: 45
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Re: Broken U-bolt Help
I replaced 3 of the four u-bolts yesterday the guy at the dealer gave me 7 correct size nuts and nowhere sells 9/16" nuts. but the po didnt line up the holes in the cross shaft with the dowel so the front of both shafts were not tight in the cradle. So im hoping that was the whole problem.
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67 c-10 lwb 81 trans-am (in 1000 pieces) 92 firebird (pos) 63 austin heally sprite (future project) 58 chevy pickup (future project) |
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#15 |
Registered User
Join Date: Oct 2007
Location: Sykesville MD
Posts: 357
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Re: Broken U-bolt Help
67lngbd, google Fastenal, they are a bolt distributor and have a bunch of baltimore locations, only thing is they sell stuff in packs, any kinda bolt/nut you can think of, even grade 14 for the military
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#16 |
Senior Member
Join Date: May 2004
Location: johnstown, NY
Posts: 2,393
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Re: Broken U-bolt Help
Ok so what is the torque supposed to be on the new 9/16" ubolts. My 69 chassis manual says 40 but that is for the stock 1/2" ubolt. The 9/16" must be more than 40. I found the attached word file that says 85, but seems like quite a difference. It sounds like this is important to torque correctly, so that is why i'm asking.
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#17 |
Registered User
Join Date: Sep 2007
Location: baltimore md
Posts: 45
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Re: Broken U-bolt Help
I probably should have asked that question myself. I just made them very tight and used red locktite just to make sure they didnt fall off. Let me know If you find out for sure.
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67 c-10 lwb 81 trans-am (in 1000 pieces) 92 firebird (pos) 63 austin heally sprite (future project) 58 chevy pickup (future project) |
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#18 |
Registered User
Join Date: Dec 2007
Location: Santa Maria, Ca.
Posts: 1,423
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Re: Broken U-bolt Help
The nuts on those u bolts are crimp lock nuts and are not supposed to be reused. I had a shop put an a-arm on my one ton and the u bolts worked there way off in less than a month
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