which body bushings should I get?
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jiho said:
All torque values are threads clean and dry unless otherwise specified.. The lube changes the torque value required to achieve the required clamping force. If you torque a lubed bolt to the torque spec of a dry bolt you have over torqued it. Do you really think that the lower numbers they put on the charts for a lubed torque compare to a dry torque mean that once you lube a bolt it becomes weaker?
pontiacgp said:
What is your source for this statement? I assume you mean the values given by GM in the shop manuals.
Me, I've always assumed that when one value is given it means "lightly lubricated" threads, like from a dab of oil on your finger, and when a range is given it means "heavily lubricated" at the low end and "dry" at the high end.
We seem to be having this flame war in two different threads at the same time.
jiho said:
Thats common knowledge in the fastener industry. Which begs the question where do you get this info? Just a random assumption??
jiho said:
ve3oky said:
We're not talking about the fastener industry, we're talking about the auto industry, specifically GM shop manuals. Torque specs in GM shop manuals are the issue.
My assumption originated with a onetime landlord, an old bird from Kansas who taught (or so he said) at a GM school for dealer mechanics in Kansas City (I think that's where he said) back in the '60s or '70s. It is backed by the only statements I can find in the GM manuals I have. In the few cases where thread treatment is mentioned, they specify "lightly lubricated."
For example: "These specifications are for clean and lightly-lubricated threads only. Dry or dirty threads produce friction which prevents accurate measurements of the actual torque."
They never say anything (that I've seen) about assuming dry threads, which would make no sense anyway.
Most bolts are lubricated out of the box: black oil-and-phosphorus, zinc or cadmium plated. GM generally used and sold black oil-and-phosphorus. If the specs were dry, mechanics would be over-torquing the bolts they were given to use.
So those tidbits and common sense facts are the basis of my assumption. Which obviously doesn't prove I'm right. Lord knows common sense hasn't always prevailed....
EDIT: I must add that it's also obvious that in my memory of the old bird, I may have it a little confused as to what he said. He did give me the tip about a dab of oil, but thinking about it I'm not really certain that he said anything about GM torque specs.
EDIT EDIT: Anyway, I knew him 25 years ago and he's dead.
jiho said:
Where do you think GM gets the fasteners from ... the fastener industry, I know this because I've sold to the Oshawa, Ontario GM plant. They are very specific about what they want and what the specs are. Like 99% of the worlds industries you can not supply a product to them stating specs that makes "assumptions", i.e. if a foreign object was used to modify the specs like a lubricant. If no foreign object was used then it was not stated (dry specs), if one was used you have to specify critical data like make and type because obviously using motor oil is going to be different then using Graphite or lithium grease. So yes ALWAYS unless specified it IS dry spec you cant make a random assumption as to what they used and how much. Even those books that specify "lightly lubricated" will list it some where the make and type.
Assuming its anything other then dry if not specified, makes zero sense and its simply not the case.
jiho said:
Your talking about the information listed in the large 1000+ page service manuals, Yes?? Which is referring to the exact same bolts GM used to build your car with. The specs in there are for the "GM Genuine" parts you would or could have bought over the counter 30 years ago, the same ones your car came with. GM could not predict where people would actually get bolts from to put in the cars, they could only write specs based on the ones they where using. Just like any other manufacturer of a product, the information and specs are for the OEM product/parts not some Chinese knock offs or stuff ya got from your local hard wear store.
If you replace a GM zinc coated bolt with one that is not zinc coated, then yes specs will be different, cause the specs given to you in the book are for the zinc coated bolt as is, no additional lubrication, unless other wise specified.
ve3oky said:
Yes, the shop manual. And the body mount bolts I found in my car -- I've said this so many times I'm getting tired of hearing it myself -- were Class 12.9, M10x1.50. They were not zinc plated.
So the bolts GM used to build my car were 12.9, and the shop manual refers to these bolts with the torque spec of 52 lb-ft. The spec will obviously be lower if you are replacing with a sub-standard 10.9 bolt.
So what body mount bolts did people find in their cars? 10.9 or 12.9?
And what the @#$% is your BS point?
ve3oky...don't waste your time. There is nothing in the manual that states GM used 12.9 body bolts and it would be easy for someone to get a picture of a body bolt head that shows 12.9 but none are posted. GM used grade 8 - 7/16 body bolts on the A body which had substantially more power in some cases than the G body so it would make no sense that they upgraded the bolt on the G body. Car manufacturers have always take the cheapest way out so they would not use a more expensive bolt or add lubrication to the bolt if not needed. Also GM used 10.9 bolts in suspension on G body and they take more punishment than body bolts.
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