Chevy girl, first off welcome to the site.

It sounds like your speedometer cable is going bad. They tend to make noise when they start to go. I'd recommend getting one as soon as you can so you don't lose the speedo.

 

I had the same problem with my 2004 avalanche and I found a website where they fix it for $99 dollars, they also replace all the gauges and motors for something around $140 here is the site in case you wanna check it out.

www.speedometergaugerepair.com

 

Speedo drive cable rear left side of transmission toward the back pull it off then rear of speedo pull it and lube with oil or penetrating oil while spinning slowly with drill! if it doesnt free up you may have to replace it around fifteen bucks at advance auto parts
HAMMERGONE!!

 

sent mine to gmgaugerepair,com and they did it for 125.00. and you get your cluster back not somebody else's.they were the best value i found for the money and had fast service and are very professional.

 

I just had a rebuilt automatic transmission installed for my 2001 Silverado 1500 5.3L V8 2 WD. The problem is the Speedometer needle is bouncing up and down when I accelerate and on the freeway it will studder and slip.