nashdavea

I just spent 4 or 5 hours removing a trailing arm using the sawzall method. Now i have no bolt.

Any reason (except for aesthetics) I can't use a plain 7/16 x 4-1/2 bolt to replace this rather than waiting days for the real bolt? I know the correct part has the unthreaded end which you should use to drive the bolt out, but no one I have heard of has ever been able to get them out without the sawzall, so what's the point???

0Willcox Corvette

Grade 8 bolt... I'm not sure I would trust a hardware store bolt holding my rear wheel on.

i can post you a set by USPS and if you are close enough they may get there Saturday... I'm not sure what their schedule for pick up and delivery is like...

Just a thought....

Willcox

Mike Ward

The trailing arm pivot bolts applies 100% of the forward thrust to move the car and all of rear braking action. I wouldn't use anything other than the correct bolt.

babbah

Glassbowtie77

+1

sly vette

Yep!

There are a few bolts you may substitute a lesser grade for...This is NOT one of them!

nashdavea

Thanks to all of you, particularly Willcox, who gave a logical answer. If you look up the shear strength of 7/16 bolts, a grade 8 bolt will shear at 17,378 lbs. A grade 5 bolt will shear at 14,322. In my other life I'm an aircraft mechanic, and the wings of many older airplanes capable of pulling 4-5 Gs are held on by 3 each 1/4" bolts (grade 8). I don't think my 18 year old son can put 18K of stress on this bolt (which shares the load with the bolt on the other side) given that the car weighs only 3900 lbs. I'm on my way to buy a pack of grade 8 bolts so he can drive the car while he's on Winter break from the Air Force Academy.

mapman

Can you tell us what airline you work for, and do they source fasteners from the local hardware store?

C3Dave

You got the advice you asked for. Why did you bother asking if you weren't gonna listen to it anyways?

nashdavea

Sorry, C3Dave et al, I was looking for someone who might have done this and had some useful advice. I took the advice from Willcox, the professionals, from whom I've bought quite a few items - I replaced with a grade 8 bolt. To satisfy my curiosity I wire brushed the head of the original bolt, and it's a GRADE 5 bolt. All the rest of the "advice" was clearly based on complete lack of technical knowledge. I don't appreciate the attacks - I bought the car and spent a year rebuilding it for my sons, and as soon as we put it on the road we discovered the wheel bearings bad. I wanted to get it going as fast as possible so they could drive it over Christmas break, so I ordered the trailing arm assy. If I have to do the other side I'll know enough to order the shim kit and bolt as well. In order to get it going before they go back to school, a substitution was most expedient. Based on the FACT that the old bolt is grade 5 and I substituted with grade 8, I know this is a safe repair. Let's stick to positive advice when we know the facts.

And btw mapman, you can't get grade 8 bolts at your local hardware store. I had to go to a commercial fastener supplier about 25 min from home. And most all airlines have professional engineers who routinely approve substitutions of parts with parts of equal or better quality when the original parts are not available. What a lame post.

moosie982

Peace,,, & have a Merry Christmas etc. moosie

Tom454

I just replaced a Grade 8, 6 inch UHL 3/8-16 alternator mounting bolt on my Silverado with the identical bolt from Home Depot. Even the thread length was correct. It was $1.68 as opposed to the same part from a truck parts supply company for $11.75. I was surprised Home Depot had it. Almost didn't bother going there. Same thing happened for some very large backhoe fasteners I needed. Just a heads up.

69 Chevy

I don't own a Sawzall. I didn't need one to remove my trailing arm pivot bolts when I replaced the OEM bushings. And I said so in a few posts on the subject this past year, like the one where we made recommendations on the easiest way to install the new bolts...(a long-nosed, needle-nosed pliers was my choice.) You must not have read them. But now you know at least one person who didn't spend 4 or 5 hours sawing away at grade 5 bolts.

Since you already made your decision on what fasteners to use, my point is moot. But since I'm already posting on your thread I'll throw in my 2 cents anyway. First, I guess I'm just lucky to have multiple hardware stores in my neck of the woods that stock grade 3, 5 and 8 fasteners. All Ace hardware stores stock Hillman brand fasteners.

The biggest selection, and priced by the pound, is Tractor Supply. I would have no undue concern of substituting one of their bolts in place of the original. As long as the bolt shank was not threaded its complete length. But most hardware store type capscrews usually are. Even so, I would use them in a pinch but would replace with the correct OEM style bolt at my earliest convenience.

redvetracr

most of my suspension bolts came from John Deere, just use a good quality bolt and get the "grip" and "thread" as close to original as possible. I also used a metal lock nut instead of a nylock or the original castle nut and cotter pin on the t-arm bolt.

Mike Ward

And Merry Xmas to you too. Lots of luck with any future questions.

mapman

Sorry you consider my post to be lame, I was trying to warn you about using common source fasteners for critical applications.

FWIW my local hardware store does carry Grade 8 bolts, as do Lowes, Home Depot, etc. And for NON CRITICAL applications, I've got no problem using their proper grade bolts. Problem is, you don't know the production history and quality control standards for these fasteners. For CRITICAL applications I obtain the proper fastener, they are readily available from a variety of vendors. A good local source of quality fasteners would be your Caterpillar dealer.

My work experience was in aircraft manufacture and am aware of the process for component substitutions, I've also seen the results of counterfeit components finding their way on aircraft. Ask yourself, how many times did your engineers approval process result in obtaining components from the local hardware store. Not trying to be lame, just trying to help you avoid a bad day. Good luck.

Wishing you and your family a Merry Christmas.

forvicjr

Not to start any trouble here,my personal opinion. Theres some parts on these cars that I wouldnt change without a GM part number,or a high end aftermarket. Theres also some that I would change. The bolt in question is one of them. I disagree with the fact that if the general put it there its the only correct part. Do i think the factory should have put a grade 8 bolt in the trailing arm,yes. Do i think the bean counters said no due to expence and overkill ,yes. I also agree with what was said above, dont deviate from the design of the bolt no more than you have to, but going from grade 5 to grade 8,what in the hell is wrong with that? There again my opinion here and some like mine ,some dont.

jnb5101

as forvicjr stated, i don't think the general used special-ultra-strong-unobtainium-nasa grade bolts. they weren't building the space shuttle. they were building a car that had an expected life of 8 years. ace hardware has a great selection of grade 5 and 8 coarse and fine thread fasteners. could one be defective and break? sure, as could a factory bolt, or one of the chinese made replacements.

CA-Legal-Vette

I doubt there is much downside to upgrading to a bolt with a higher tensile strength and corrosion resistance.

IIRC the TA bolt does have a reduced thread diameter but I don't remember if this is critical for fit. A castle nut would be a good idea to secure it but drilling a hole through a grade 8 bolt isn't much fun.

I do know that some vendors offer the TA bolt in grade 8 but I don't know if the factory original one was.

babbah