Lost Bolts Please Help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jp-n-mallory71 · 04-09-2006, 05:45 PM

I lost my trailing arm bolts that attach the arm to the cross member can i use grade 8 bolts and if so what size and what threads are they coarse or fine

THANKS
JOHNNY

qksilver · 04-09-2006, 08:45 PM

Check with one of the board vendors......they sell the right type. You need a shouldered bolt , hard to find that large.

4x4Poet · 04-09-2006, 11:46 PM

Those are pretty big bolts to just looose!

Ok, I've done worse. Much worse...

COBRO · 04-09-2006, 11:58 PM

They are 4"X3/4". And yes I would recommend using grade 8 - thats what I used and in fine thread and also used nylok nuts instead of the regular nut&lock washer.:::::::CB

4x4Poet · 04-10-2006, 12:02 AM

BTW, the torque setting on the control arm bolts is 145 ft lbs.

So grade 8 minimum is mandatory.

COBRO · 04-10-2006, 12:11 AM

The stock bolts that came in the truck are grade 5 as are most replacements that say LMC will sell you,they are course thread with a lock washer so moving up to grade 8 is a great improvement over stock. You can buy the grade 8 in either course or fine thread but again the fine threads are stronger compared to course.::::::CB

Fred T · 04-10-2006, 11:06 AM

3/4-10 X 4" is the size the factory used. You can buy them in grade 8 at a hardware or farm store. The cad plate finish (gold color) is far better than the zinc plate on most grade 5s. Strength wise, you don't need the fine thread. Get new nuts, too. And put them on with Loctite. It not only helps keep the nut on, but will seal out moisture so they don't rust together.

4x4Poet · 04-11-2006, 04:22 AM

COBRO is right. I'm wrong. Those 3/4" bolts are hefty, so I forgot that they wouldn't need to be grade 8. Just last week I finished removing, rustproofing, installing poly bushings, and reinstalling the trailing arms on my C10 burb. I never checked the bolt grade. I just cringed a little as I torqued both the trailing arm bushing bolts and new U-bolts to 145 ft lbs. Dat's alotta torque.

COBRO · 04-11-2006, 11:01 AM

4x4 your not wrong - I agree that grade 8 is mandatory. GM used grade 5 when they built it so who am I to say they dont know what they are doing. When I replace bolts on the suspension I always go with the best I can find.
I have never understood when some say you dont need it that strong,but whatever flys their kite.:::::::::::::CB

04-09-2006, 05:45 PM	#1
jp-n-mallory71 Registered User Join Date: Apr 2005 Location: san marcos tx. Posts: 38	Lost Bolts Please Help I lost my trailing arm bolts that attach the arm to the cross member can i use grade 8 bolts and if so what size and what threads are they coarse or fine THANKS JOHNNY

04-09-2006, 08:45 PM	#2
qksilver Senior Member Join Date: Dec 2004 Location: Southern Pines NC Posts: 3,853	Re: Lost Bolts Please Help Check with one of the board vendors......they sell the right type. You need a shouldered bolt , hard to find that large.

04-09-2006, 11:46 PM	#3
4x4Poet Registered User Join Date: Nov 2004 Location: "Under Montana skies." Posts: 1,836	Re: Lost Bolts Please Help Those are pretty big bolts to just looose! Ok, I've done worse. Much worse... __________________ '71 GMC K20 Suburban, '71 GMC K10 Suburban, '72 Chevy C10 CST Suburban, '72 Chevy K20 clunker pickup.

04-09-2006, 11:58 PM	#4
COBRO Active Member Join Date: Jan 2005 Location: RDM,Oregon Posts: 285	Re: Lost Bolts Please Help They are 4"X3/4". And yes I would recommend using grade 8 - thats what I used and in fine thread and also used nylok nuts instead of the regular nut&lock washer.:::::::CB

04-10-2006, 12:02 AM	#5
4x4Poet Registered User Join Date: Nov 2004 Location: "Under Montana skies." Posts: 1,836	Re: Lost Bolts Please Help BTW, the torque setting on the control arm bolts is 145 ft lbs. So grade 8 minimum is mandatory. __________________ '71 GMC K20 Suburban, '71 GMC K10 Suburban, '72 Chevy C10 CST Suburban, '72 Chevy K20 clunker pickup.

04-10-2006, 12:11 AM	#6
COBRO Active Member Join Date: Jan 2005 Location: RDM,Oregon Posts: 285	Re: Lost Bolts Please Help The stock bolts that came in the truck are grade 5 as are most replacements that say LMC will sell you,they are course thread with a lock washer so moving up to grade 8 is a great improvement over stock. You can buy the grade 8 in either course or fine thread but again the fine threads are stronger compared to course.::::::CB

04-10-2006, 11:06 AM	#7
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Re: Lost Bolts Please Help 3/4-10 X 4" is the size the factory used. You can buy them in grade 8 at a hardware or farm store. The cad plate finish (gold color) is far better than the zinc plate on most grade 5s. Strength wise, you don't need the fine thread. Get new nuts, too. And put them on with Loctite. It not only helps keep the nut on, but will seal out moisture so they don't rust together. __________________ Fred There is no such thing as too much cam...just not enough engine.

04-11-2006, 04:22 AM	#8
4x4Poet Registered User Join Date: Nov 2004 Location: "Under Montana skies." Posts: 1,836	COBRO is right. I'm wrong. Those 3/4" bolts are hefty, so I forgot that they wouldn't need to be grade 8. Just last week I finished removing, rustproofing, installing poly bushings, and reinstalling the trailing arms on my C10 burb. I never checked the bolt grade. I just cringed a little as I torqued both the trailing arm bushing bolts and new U-bolts to 145 ft lbs. Dat's alotta torque. __________________ '71 GMC K20 Suburban, '71 GMC K10 Suburban, '72 Chevy C10 CST Suburban, '72 Chevy K20 clunker pickup.

04-11-2006, 11:01 AM	#9
COBRO Active Member Join Date: Jan 2005 Location: RDM,Oregon Posts: 285	Re: Lost Bolts Please Help 4x4 your not wrong - I agree that grade 8 is mandatory. GM used grade 5 when they built it so who am I to say they dont know what they are doing. When I replace bolts on the suspension I always go with the best I can find. I have never understood when some say you dont need it that strong,but whatever flys their kite.:::::::::::::CB



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