I had a lower a-arm u-bolt break. You should change yours too. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Injected68LS1 · 09-29-2003, 10:44 PM

My 68 is a half-ton and came with drum brakes. On these trucks, the lower control arm shaft attaches to the crossmember with two 3/8 u-bolts. Chevy increased the size of these on disc brake trucks because they were breaking.

I finally had one break that I'm sure was 35 years old. Luckily for me it was in a parking lot. I was just idling in reverse with the wheel cranked. SNAP. Not 5 minutes before I was on a major freeway doing 80mph. It was quite surprizing.

So from my experience, I urge all of you to upgrade these bolts for safety. Early Classic has a 9/16 thread ubolt kit that they sell when upgrading to disc brakes. I just finished installing them and I feel much better and safer.

BLACK AND BLUE 67-72 · 09-29-2003, 10:58 PM

OOH, That sounds suprizingly familiar my 67' GMC did the exact same thing in reverse when turning to the right in my buddy's driveway, I had to call another buddy to get the parts and a jack for me, right before I had been on the highway running 65-70 mph. Then I had the same thing happen about a year later on the same side the passenger's when turining to the right hard.
Has anyone else had this problem?

Spoof · 09-29-2003, 11:34 PM

I think we should lobby for a recall.

orange71 · 09-29-2003, 11:37 PM

Ya i had one break and i didnt know it. I finally drove it home(about 15 miles) and noticed that one side was sitting lower and i looked down at the arm and it was hanging down on one side. I was pretty lucky that the arm never dropped!!!!!!!
Chris

Hooter · 09-30-2003, 12:09 AM

ok Im gonna go into my garage and look right now!

Hooter · 09-30-2003, 12:13 AM

nope not broken, so that wasn't the clunk im hearin, but my steering box must of just started leaking, oh well

Injected68LS1 · 09-30-2003, 01:05 AM

I've driven my truck hard for about 8 years. I guess I got a lot of use out of that u-bolt.

SLS · 09-30-2003, 02:26 AM

I believe it may be a good idea to occasionally check the U-bolts that attach the rear axle to the trailing arms (on coil type rear suspension).

While redoing my 71 I removed the bed and while I have it off decided to replace some brake lines and brake components, the real coils, differential seal and gasket...whatever I noticed needing work...and do the painting of all that stuff. I even had a new driveshaft fabbed up for it.

Now that I had a good, open view of the rear workings I noticed that the cups that hold the coil springs in place were rusted through on one side. The lower cups are perfect for holding water...

There are also brackets that hold the aformentiond rear axle u-bolts in place atop the trailing arms which have a raised 'lip' around them...thus trapping water also. One of the u-bolts on my truck was rusted down to about half of it's original thickness where water had collected atop the bracket.

Like I told my wife...the more I dig into this project...the more stuff I find to replace. I might have an original bolt or two left when its all over. LOL.

JJR · 09-30-2003, 07:04 AM

Same thing happened to my brother-in-laws 65 C-10. He was slowly taking a turn and one snaped. You can get the 1/2" U-bolts from your local Chevy dealer. I will be upgrading to the 1/2" when I re-do my front suspension.

lewi · 09-30-2003, 06:25 PM

Not just the older ones do this. My 71 did the same thing and it has the disk brakes up front. If you haven't replaced them do it before it's to late.

palallin · 09-30-2003, 10:27 PM

I had one break on my '67. Made him darned hard to steer

BLACK AND BLUE 67-72 · 09-30-2003, 10:32 PM

Sounds contageous!!

And pretty dangerous!!

*67Fleetsidedream* · 09-30-2003, 10:37 PM

Wow I am paranoid now..... Where can we get them 1/2in u-bolts for the front A-arms? Besides Early Classic.

GMC JUNKIE TOO · 09-30-2003, 10:48 PM

So for the upgrade all we have to do is drill the holes larger in the crosmember. sounds like a good Idea.

*67Fleetsidedream* · 10-01-2003, 12:22 PM

This seems to be a common problem..

GMC JUNKIE TOO · 10-01-2003, 12:31 PM

Another board member swervin ervin had one of the studs that holds rhe uper control arms on break its an epidemic

**COBALT** · 10-01-2003, 12:34 PM

It is.

When I rebuilt my front/back suspension last fall I used all new hardware INCLUDING grade 8 A-arm u-bolts in the front and grade 8 U-bolts throught the trailing arms. I didn't even bother to recycle them. I also noticed when I got the front u-bolts out they were deformed - meaning they had been twisted so that the threaded ends didn't even match up.

I think the fact that grade 5 bolts as original equipment is the problem. The metal is more ductile, and is allowed to flex (which is not entirely a bad thing), but when combined with continual stress due to cyclic loading the deformation due to torsion can make the lower part of the "U" harder than the rest of the bolt. Ultimately that's where the stress is concentrated.

A grade 8 bolt is harder but a bit more brittle, but it will distribute stress more evenly and won't result in one part of the bolt being more ductile than other parts, which is why it breaks.

To replace them just put your jack up against the center bar, yank them out, and put new ones back in, and torque to spec. Pretty easy. Recheck their tightness after alignment.

Suicide-D · 10-01-2003, 02:03 PM

I had one fall off on the freeway.... yes fell off, the nuts were still on top of the control arm... The dealer still stocks them... mine was on a 71 though. I kept hearing something scraping when I hit little bumps ... I thought it was my collectors scraping until I pulled over. I had to tow it home... thank the lord it was the back one and not the front.... that could've made a mess.

mcmlxix · 12-12-2003, 05:57 PM

COBALT
Do you (or anyone else) have the dimnesions for the lower controal arm bolts?
And the dimensions for the rear u/bolts as well ...

Another question, are they the same for 67-72?
I have a 71 C/10 with power steering. .. ..

**old Rusty C10** · 12-12-2003, 06:28 PM

its a good idea to replace em hell i always check the bolts on the front end every year or thereabouts when i do brakes and front end checks noones safety is worth the cost of a bolt and check the rear too

09-29-2003, 10:44 PM	#1
Injected68LS1 Registered User Join Date: Jul 2003 Location: So. Cal. Posts: 389	I had a lower a-arm u-bolt break. You should change yours too. My 68 is a half-ton and came with drum brakes. On these trucks, the lower control arm shaft attaches to the crossmember with two 3/8 u-bolts. Chevy increased the size of these on disc brake trucks because they were breaking. I finally had one break that I'm sure was 35 years old. Luckily for me it was in a parking lot. I was just idling in reverse with the wheel cranked. SNAP. Not 5 minutes before I was on a major freeway doing 80mph. It was quite surprizing. So from my experience, I urge all of you to upgrade these bolts for safety. Early Classic has a 9/16 thread ubolt kit that they sell when upgrading to disc brakes. I just finished installing them and I feel much better and safer. __________________ 1968 Chev SWB with 1998 Corvette LS1 305hp and 320 ftlb to the wheels (stock engine!) AEM EMS and wideband O2 sensors Bowtie Overdrive's 700R4, stage 3 Baer 4 wheel discs and 20s http://iciclelanding.com/aperture?album=2049&view=album

09-29-2003, 10:58 PM	#2
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	OOH, That sounds suprizingly familiar my 67' GMC did the exact same thing in reverse when turning to the right in my buddy's driveway, I had to call another buddy to get the parts and a jack for me, right before I had been on the highway running 65-70 mph. Then I had the same thing happen about a year later on the same side the passenger's when turining to the right hard. Has anyone else had this problem? __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

09-29-2003, 11:34 PM	#3
Spoof Registered User Join Date: Jul 2000 Location: Victoria,BC, Canada Posts: 1,300	I think we should lobby for a recall. __________________ 71 GMC 1500 LWB

09-30-2003, 12:09 AM	#5
Hooter My other Love Join Date: Aug 2001 Location: Castlegar B.C. Canada Posts: 4,085	ok Im gonna go into my garage and look right now! __________________ Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life

09-30-2003, 12:13 AM	#6
Hooter My other Love Join Date: Aug 2001 Location: Castlegar B.C. Canada Posts: 4,085	nope not broken, so that wasn't the clunk im hearin, but my steering box must of just started leaking, oh well __________________ Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life

09-29-2003, 11:37 PM	#4
orange71 Registered User Join Date: Sep 2002 Location: upland, california Posts: 146	Ya i had one break and i didnt know it. I finally drove it home(about 15 miles) and noticed that one side was sitting lower and i looked down at the arm and it was hanging down on one side. I was pretty lucky that the arm never dropped!!!!!!! Chris

09-30-2003, 01:05 AM	#7
Injected68LS1 Registered User Join Date: Jul 2003 Location: So. Cal. Posts: 389	I've driven my truck hard for about 8 years. I guess I got a lot of use out of that u-bolt. __________________ 1968 Chev SWB with 1998 Corvette LS1 305hp and 320 ftlb to the wheels (stock engine!) AEM EMS and wideband O2 sensors Bowtie Overdrive's 700R4, stage 3 Baer 4 wheel discs and 20s http://iciclelanding.com/aperture?album=2049&view=album

09-30-2003, 02:26 AM	#8
SLS Finish the'71..or bust! Join Date: Jun 2003 Location: Nashville, TN. Posts: 441	Speaking of U-Bolts... I believe it may be a good idea to occasionally check the U-bolts that attach the rear axle to the trailing arms (on coil type rear suspension). While redoing my 71 I removed the bed and while I have it off decided to replace some brake lines and brake components, the real coils, differential seal and gasket...whatever I noticed needing work...and do the painting of all that stuff. I even had a new driveshaft fabbed up for it. Now that I had a good, open view of the rear workings I noticed that the cups that hold the coil springs in place were rusted through on one side. The lower cups are perfect for holding water... There are also brackets that hold the aformentiond rear axle u-bolts in place atop the trailing arms which have a raised 'lip' around them...thus trapping water also. One of the u-bolts on my truck was rusted down to about half of it's original thickness where water had collected atop the bracket. Like I told my wife...the more I dig into this project...the more stuff I find to replace. I might have an original bolt or two left when its all over. LOL.

09-30-2003, 07:04 AM	#9
JJR Registered User Join Date: Apr 2000 Location: Leesburg, GA Posts: 746	Same thing happened to my brother-in-laws 65 C-10. He was slowly taking a turn and one snaped. You can get the 1/2" U-bolts from your local Chevy dealer. I will be upgrading to the 1/2" when I re-do my front suspension. __________________ FOUNDING MEMBER OF THE DRUM BRAKE CLUB Second Owner 70 C-10 Second Owner 93 GMC C1500 Third Owner 99 C2500 Crew Cab Short Bed

09-30-2003, 06:25 PM	#10
lewi Registered User Join Date: Nov 2002 Location: Redding California Posts: 223	Not just the older ones do this. My 71 did the same thing and it has the disk brakes up front. If you haven't replaced them do it before it's to late. __________________ 1971 Chevy Cheyenne 383/350 LWB 2wd Built to use, and look good.

09-30-2003, 10:27 PM	#11
palallin Registered User Join Date: Jul 2002 Location: St. James, MO Posts: 1,238	I had one break on my '67. Made him darned hard to steer __________________ '69 Longstep K-10: 327/SM465/T-221/Closed Knuckle Dana44/12-bolt.

09-30-2003, 10:32 PM	#12
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	Sounds contageous!! And pretty dangerous!! __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

09-30-2003, 10:37 PM	#13
67Fleetsidedream Wiseass secured himself a BAN Join Date: Nov 2000 Location: MOON!!! Posts: 2,282	Wow I am paranoid now..... Where can we get them 1/2in u-bolts for the front A-arms? Besides Early Classic.

09-30-2003, 10:48 PM	#14
GMC JUNKIE TOO THE QUICKER FIXERUPER Join Date: Jul 2002 Location: Ok Posts: 615	So for the upgrade all we have to do is drill the holes larger in the crosmember. sounds like a good Idea.

10-01-2003, 12:22 PM	#15
67Fleetsidedream Wiseass secured himself a BAN Join Date: Nov 2000 Location: MOON!!! Posts: 2,282	This seems to be a common problem.. Last edited by 67Fleetsidedream; 10-01-2003 at 12:24 PM.



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10-01-2003, 12:31 PM	#16
GMC JUNKIE TOO THE QUICKER FIXERUPER Join Date: Jul 2002 Location: Ok Posts: 615	Another board member swervin ervin had one of the studs that holds rhe uper control arms on break its an epidemic

10-01-2003, 12:34 PM	#17
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	It is. When I rebuilt my front/back suspension last fall I used all new hardware INCLUDING grade 8 A-arm u-bolts in the front and grade 8 U-bolts throught the trailing arms. I didn't even bother to recycle them. I also noticed when I got the front u-bolts out they were deformed - meaning they had been twisted so that the threaded ends didn't even match up. I think the fact that grade 5 bolts as original equipment is the problem. The metal is more ductile, and is allowed to flex (which is not entirely a bad thing), but when combined with continual stress due to cyclic loading the deformation due to torsion can make the lower part of the "U" harder than the rest of the bolt. Ultimately that's where the stress is concentrated. A grade 8 bolt is harder but a bit more brittle, but it will distribute stress more evenly and won't result in one part of the bolt being more ductile than other parts, which is why it breaks. To replace them just put your jack up against the center bar, yank them out, and put new ones back in, and torque to spec. Pretty easy. Recheck their tightness after alignment. __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

10-01-2003, 02:03 PM	#18
Suicide-D Registered User Join Date: Jan 2001 Location: Katy, TX...but the love of my life resides in Dublin,OH. Posts: 1,408	I had one fall off on the freeway.... yes fell off, the nuts were still on top of the control arm... The dealer still stocks them... mine was on a 71 though. I kept hearing something scraping when I hit little bumps ... I thought it was my collectors scraping until I pulled over. I had to tow it home... thank the lord it was the back one and not the front.... that could've made a mess.

12-12-2003, 05:57 PM	#19
mcmlxix Collector of Projects Join Date: Apr 2003 Location: Las Vegas Posts: 3,106	COBALT Do you (or anyone else) have the dimnesions for the lower controal arm bolts? And the dimensions for the rear u/bolts as well ... Another question, are they the same for 67-72? I have a 71 C/10 with power steering. .. .. __________________ Rich 1972 K5 Blazer CST Click HERE D60 BIG BRAKE UPGRADE Click HERE

12-12-2003, 06:28 PM	#20
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,313	its a good idea to replace em hell i always check the bolts on the front end every year or thereabouts when i do brakes and front end checks noones safety is worth the cost of a bolt and check the rear too __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

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