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I won't bore everyone with the hows and whys of the problem, but it seems that the bolt that mounts the alternator to the bracket (this is the bolt the alternator pivots on) on my truck ('80 F-150, 4.9L engine) has disappeared. The only thing holding the alternator in the engine was the smaller bolt on the bottom used for adjustment! Fortunately, I decided to troubleshoot that odd rattling noise from the engine room fairly quickly, or there's no telling what would have happened when the whole thing came loose.
My problem is, I don't know the correct bolt to replace it with. I'm sure it's been mentioned somewhere on this forum before, but I couldn't find it in the first fifty threads my search turned up. So if anyone happens to know and could share the info (preferably sooner than later - I really need the truck this weekend), it would be greatly appreciated!
It's hard to be sure - my alternator is mounted under the dealer-installed A/C compressor, so it's just about impossible to see. I *think* it is the one on the right. If the one on the left has that nut permanently attached to the bracket, then it is definitely the one on the right.
Hmmm, anyone? I'm heading to the hardware store after work; I can probably come up with a pretty close approximation on my own, but if anyone's got one of these laying around, it would sure be nice to know for certain.
On both styles show in the photos above, the bolt threads into the bracket.
The direction the bolt goes in is different on both types of brackets.
I would also buy a 5/16 5 inch long bolt with a matching self locking nut, and extra washer for filler.
This should go through and get you by until you find the correct bolt.
As it turns out, I have neither of the two pictured brackets. Because my truck has dealer-installed air conditioning, I have a combination A/C-alternator bracket. The missing bolt doesn't thread into the bracket, it just passes through it and is secured by a nut.
I ended up buying a 4.5" long 3/8" bolt with lock washer and matching nut, and that seems to have done the trick. It *might* take a 7/16" bolt as the 3/8" feels a bit loose, but it's good enough for now and the truck is ready to go this weekend. Thanks for the help!