Crazy, Terrible, Weird Random Grinding

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Apr 14, 2012
Whitefish, MT
After spending about an hour searching the forum I could only find one post even remotely close to the issue I'm having and it had no replies so here's hoping someone can help me. My wife and I live in SoCal and it's her LC. Anytime we've visited Lake Arrowhead, (very twisty mountain roads, lots of elevation change), here truck makes a small rattle like sound, something similar to a heat shield vibrating, every time we accelerate up a hill. If it's not uphill it doesn't make the sound. We were up over the weekend so I could use my friends lift to make changing the starter and fuel filter easier. Completed that, along with belts and an oil change, no issue. Only now anytime we accelerate up a hill from standstill, or at speeds below 30mph the noise is there, but is a very loud grind/squealing metal on metal sound. If you let off the gas it goes away completely and doesn't come back if you're easy on the go pedal. If you're at speeds above 30mph, no sound no issue. Drove it the 90 miles back from Lake Arrowhead to home and the only time it made the sound was going up a hill from a dead stop. Searching the forum for similar issues all I could find was trouble with loud grinding during the starting process, which I don't have. To be clear, there is no grinding or strange sound of any kind on startup. It did make the same sound, though not as extreme, when I started it the first time after changing the parts. Crawled under the truck and I'm 99% sure the sound is coming from the flywheel housing, leaving me at a total loss. What could it be? Thanks in advance for the help!
In the first part of your post you state "here truck makes a small rattle like sound, something similar to a heat shield vibrating", then later you state "but is a very loud grind/squealing metal on metal sound". Are you referring to the same noise and it has gotten worse? At the end you state "It did make the same sound, though not as extreme, when I started it the first time after changing the parts."

Based upon your first description I would have guessed it as being spark knock or pre-ignition. Higher load, thinner air and higher temps along with incorrect ignition timing being the cause. Poor or low octane fuel.

Based upon the second description it may be something like a stripped drive flange on one of the front wheels. If you have added a CDL switch enable that or shift into low range to see it the problem still occurs. If its gone then zero in on the drive flanges.

The last comment implies that you were parked. That noise might be the starter staying engaged, but you state the starter was replaced. Was that last noise with the transmission in Park or Neutral? Try shifting into gear and keep the brakes on, then rev the engine. Report back what you find.
I too have the same sound , very hard to find. I just rebuilt the starter and the sound is now there. I took it out and bench tested it and everything seems fine, I even put the same gear back in thinking that the new gear wasn't matched to the fly wheel but no difference. The noise was constant at first and now just under load at below 30 mph. I puzzled as well

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I just ground the gear teeth on the starter back an 1/8 of an inch and now the starter works fine and no more noise , hope this helps

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Thanks for all the info guys, and I apologize for any confusion from my first post. I decided to take it to my mechanic to see if he was able to diagnose the problem. He couldn't do any better than I did initially only determining that it was coming from the flywheel area. However, when he put a washer on the front bolt the sound went away completely. Since I bought an aftermarket starter from O'Reilly we figured maybe that was the problem as the original starter didn't make the same noise.
So we ordered up starter from the Toyota dealer thinking true OEM equipment would fix the issue. No luck. There are only two things left that I, or my mechanic, can think of that would be the issue. One, there is some sort of shim that was on the original starter that I missed when I switched them out earlier. So my question to the forum: is there a shim/plate/washer/something that I missed and I need to have to make this work correctly? When we asked the dealer they had nothing in their system for any such part. The only other option I'm left with is a bent flywheel, which sucks to say the least but I guess I'll deal. My wife loves the truck and doesn't want anything else so we're willing to put the money into it to fix it the right way. Thanks again for the help!

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