Buzz at 40 mph.

[dreman]

With 246,000 miles on it this may be a late question, but I thought I'd give it a shot. Ever since we bought our Sierra new in 1999, it has buzzed as soon as it hits 40mph in 4th gear. It goes away at about 42 or 43 mph, but it hits 4th right about the same time it hits 40mph almost every time. The buzz seems to be coming from the dash/steering/under the truck somewhere. I never have been able to pinpont it exactly. My truck is a short bed std cab with a 4.3 v6 and 4L60E trans.

 

I guess I eventually got used to it, but reading other posts here reminded me. If it's too involved or requires a trip to the dealer I may not mess with it, but I thought I'd give it a try.

[Sierra54]

I've had the same issue since the 2nd transmission service at about 140,000. Both times I've had the pan dropped & filter replaced. I thought it was a loose heat shield but everything seemed snug. Now I simply don't linger around 43 mph. I'd also appreciate any suggestions.

[z85violator]

stock exhaust? resonace?