How strong are half shaft u-bolts?

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Feb 19, 2010 | 09:39 PM

sting66cp

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Racer

Joined: May 2004

Posts: 288

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From: Tigard OR

How strong are half shaft u-bolts?

I'm re-doing the rear suspension in my 69 small block. I have a 400HP 383, 700r4, and 3.08 gears. How strong are the u-bolts on the half shaft at the differential yokes? Is there an advantage to upgrading to big block yokes, or the Drag Vette billet caps? Or do I not need to be concerned at this power level? Has anyone purchased these caps?

http://www.dragvette.com/products.htm

Feb 19, 2010 | 10:44 PM

OMF

Melting Slicks

Joined: Jul 2006

Posts: 2,274

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From: Salmon Arm, BC

I don't think you need to be concerned. I have the same setup with a 425HP 406, and have had no problems.

Feb 20, 2010 | 12:25 AM

ED69ray

Pro

Joined: Dec 2008

Posts: 531

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From: Frisco TX

I think the main culprit is traction - on street tires the stock U bolts will work fine on a 400hp car.

If you are really hooking up the rear I'd look to build up everything

Feb 20, 2010 | 05:57 AM

white knuckles

Advanced

Joined: Feb 2009

Posts: 64

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From: Blairstown NJ

The U-joint is the weak link. Broke one racing last year.I got spicer solid U-Joints and have had no problems

Feb 20, 2010 | 07:45 AM

7T1vette

Team Owner

Joined: Jan 2006

Posts: 37,637

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From: Crossville TN

They are plenty strong enough...as long as you are using the correct Grade of bolt. I believe the U-joint bolts are Grade 5, so you could use either Grade 5 or Grade 8 bolts. Grade 3 bolts are fairly soft and could snap [or stretch] under load. Standard hardware store stuff is Grade 3.

Feb 20, 2010 | 07:48 AM

...Roger...

Race Director

Joined: May 2006

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From: Dayton, Ohio

I've never seen the factory u bolts break but I have seen the factory HD caps stretch, leaving the u joint loose to clunk around.

Feb 20, 2010 | 08:54 AM

hugie82

Safety Car

Joined: Mar 2007

Posts: 3,652

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From: Bridgewater nj

Quote:

Originally Posted by ...Roger...

I've never seen the factory u bolts break but I have seen the factory HD caps stretch, leaving the u joint loose to clunk around.

and usually it because a U bolt that came loose over time.

Feb 20, 2010 | 09:56 AM

sting66cp

Thread Starter

Racer

Joined: May 2004

Posts: 288

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From: Tigard OR

Quote:

Originally Posted by hugie82

and usually it because a U bolt that came loose over time.

I think the torque spec is 14 - 18 FT LBS, should you put loc-tite on these?

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Feb 20, 2010 | 11:09 AM

7T1vette

Team Owner

Joined: Jan 2006

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From: Crossville TN

They should either have split lockwashers or use French locks to prevent the bolts/nuts from backing off.

Feb 20, 2010 | 11:15 AM

#10

Mike Ward

Race Director

Joined: Jul 2001

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Quote:

Originally Posted by hugie82

and usually it because a U bolt that came loose over time.

HD caps do not use u-bolts, and vice-versa.

Feb 20, 2010 | 05:09 PM

#11

BKbroiler

Le Mans Master

Joined: May 2002

Posts: 5,084

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From: Lebanon Township New Jersey

Some people here are confusing U bolts with U joints. The OP asked about the factory U bolts and nuts that hold the inner U joints.
For what it's worth, I replaced the U bolts with the Drag Vette billet caps on mine. They fit nicely and they are holding up OK but I never had a problem with the stock U bolts either.