A friend of mine visited from California and the transmission on his 04’ Yukon is making a strange noise that no mechanics can figure out. Prepare for some “sound effects”…
He said that as he is going down a mountain in high gear, or overdrive, he takes his foot off the pedal and the transmission makes a loud “Zzzzzzzzzzzz” noise. It does not do it in any other gear, only overdrive. Also, it only makes the sound if he is going below 55 MPH.
That’s a thought. I have the same thing on my Subaru. I will mention it to him. However, he did not describe it that way. Also, a heat shield would make noise in several gears. This is only in overdrive and only when coasting down a mountain and only under 55MPH. He had to leave early so I never had the opportunity to hear the noise myself but it sounds like a tranny or maybe a rear end noise to me. I don’t know…
Regardless of the source of the noise, the OP might want to mention to his friend that flying down a mountain pass in high gear is not a good thing. If your friend wants to keep his vehicle under control and wants to keep his brakes from overheating and possibly boiling the brake fluid, he should shift down one or two gears.
My transmission is a 5-speed automatic, and on a long, steep downgrade, I shift down to 3rd gear. This allows me to maintain my speed without having to hit my brake pedal, and keeps the vehicle under control. And, if I do have to hit the brake because of another car or an animal, I know that my brakes will have their full effectiveness, unlike brakes that have already been overused for miles on a steep downgrade.
