Gear box question
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New User
Joined: Jan 2015
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Gear box question
I put a post on last week about my gear box coming off and the mechanic not wanting to fix it because he said the frame was to rusty. Many of you helped and some couldn't believe that the frame could be rusted that bad.
Well, I brought the truck home and there is some rust around one of the holes, but it is far from a shot frame. The main reason for the brake was a cobble job by the previous owner, I believe.
I bought a gearbox and had a heck of a time finding hardened bolts with the fine thread that the gear box has.
My question is, why would Ford make such an important part requiring a grade 9 hardened bolt, required to be torqued even, and make it fine thread? I ask because fine thread can strip out easier.
Well, I brought the truck home and there is some rust around one of the holes, but it is far from a shot frame. The main reason for the brake was a cobble job by the previous owner, I believe.
I bought a gearbox and had a heck of a time finding hardened bolts with the fine thread that the gear box has.
My question is, why would Ford make such an important part requiring a grade 9 hardened bolt, required to be torqued even, and make it fine thread? I ask because fine thread can strip out easier.
Lead Driver
Joined: Jan 2003
Posts: 9,893
Likes: 12
From: Ohio
Found this online in a couple places:
Fine threaded bolts are stronger than the corresponding coarse threaded bolts of the same hardness. This is in both tension and shear due to the fine threaded bolts having a slightly larger tensile stress area and minor diameter.
Fine threads have less tendency to loosen under vibration due to their having a smaller helix angle than coarse threads.
Pretty much what I have heard/know about it.
Agree, they tend to be easier to strip out if you apply too much force to them. All depending on the size of the bolt you are working with and the size of the wrench.
Fine threaded bolts are stronger than the corresponding coarse threaded bolts of the same hardness. This is in both tension and shear due to the fine threaded bolts having a slightly larger tensile stress area and minor diameter.
Fine threads have less tendency to loosen under vibration due to their having a smaller helix angle than coarse threads.
Pretty much what I have heard/know about it.
Agree, they tend to be easier to strip out if you apply too much force to them. All depending on the size of the bolt you are working with and the size of the wrench.
Fleet Owner
Joined: May 2009
Posts: 21,437
Likes: 76
From: Gilbert, PA
I put a post on last week about my gear box coming off and the mechanic not wanting to fix it because he said the frame was to rusty. Many of you helped and some couldn't believe that the frame could be rusted that bad.
Well, I brought the truck home and there is some rust around one of the holes, but it is far from a shot frame. The main reason for the brake was a cobble job by the previous owner, I believe.
I bought a gearbox and had a heck of a time finding hardened bolts with the fine thread that the gear box has.
My question is, why would Ford make such an important part requiring a grade 9 hardened bolt, required to be torqued even, and make it fine thread? I ask because fine thread can strip out easier.
Well, I brought the truck home and there is some rust around one of the holes, but it is far from a shot frame. The main reason for the brake was a cobble job by the previous owner, I believe.
I bought a gearbox and had a heck of a time finding hardened bolts with the fine thread that the gear box has.
My question is, why would Ford make such an important part requiring a grade 9 hardened bolt, required to be torqued even, and make it fine thread? I ask because fine thread can strip out easier.
If so they are 7/16 -14 (COARSE) thread and there are 3 of them
Postmaster
Joined: Nov 2011
Posts: 3,533
Likes: 17
From: SW Florida
Yeah his steering box came loose, he's got a thread here too.
https://www.ford-trucks.com/forums/1...-question.html
I don't remember them bolts being anything special. If you ever need bolts and can't find them in a junkyard for some reason, then Fastenal can MAKE bolts for you if they don't have them in stock.
https://www.ford-trucks.com/forums/1...-question.html
I don't remember them bolts being anything special. If you ever need bolts and can't find them in a junkyard for some reason, then Fastenal can MAKE bolts for you if they don't have them in stock.
Thread Starter
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New User
Joined: Jan 2015
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Mine for some reason were a fine thread, I don't know why. Even the guy at the parts store thought it was weird.
Fleet Owner
Joined: May 2009
Posts: 21,437
Likes: 76
From: Gilbert, PA
Then the same butcher who put the plate it changed the bolts. They left the factory w 7/16 coarse bolts
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