Hello all I have an '01 Tahoe with about 106k and yesterday I floored it to pass someone on the freeway and I heard a rattling noise come from the engine when it switched to the passing gear...any ideas what that could have been? Its the first time i have ever heard that noise other than the short rattling at low rpm's on a cold morning when its first started up. Any advice would be helpful. Thanks - Joe

 

Sounds like a little pre-detonation (pinging).
This can be caused by any number of things such as poor quality fuel, excessive carbon build-up in the combustion chamber, dirty fuel injectors etc.

A slight amount of pinging is acceptable but heavy pinging or knocking can cause catastrophic engine damage.
With 106,000 miles I would recommend adding four or five 12oz bottles of Techron Fuel System cleaner to a single full tank of fuel and drive it until the tank is near empty and then add two bottles to each full tank of fuel for the next couple of fill-up’s this does a very good job of both removing carbon build up and cleaning the fuel system and injectors.
I am assuming that all other scheduled maintenance has been performed according to the owners manual?

 

I still need to do the 100k maintenance....tranny flush and rear differential, fuel injector cleaning. All that will be done soon....other than that i am regular on oil changes and changed plugs and wires with OEM at 97k. I will try what you said and as for the low rpm rattle when cold I saw a GM bulletin that says its a common problem and they dont recommend replacing anything for it. Hope thats true.. here is the link to that post
https://chevroletforum.com/m_49948/tm.htm