2000 Nissan Frontier 2wd std cab automatic RUMBLES at 1200 rpm

In what is otherwise an exceptionally great truck, when the tach hits 1200 rpm, the whole cab resonates in a low frequency that just about drives one crazy. It is reproduce able on demand, and at any road speed. Rolling down the windows helps a bit to reduce the noise bouncing around in the cab. It does not seem to be anything to do with the performance or functionality of the truck. In all other respects it runs just fine. Any ideas what to do about it, or is that just the resonant frequency of e cab? Thanks! Brent

Check the universal joints in the driveshaft. Could also be a cracked flex plate between the transmission and the engine.

Thanks Keith. This has been going on since I bought it 2years ago, and never changes. Wouldn’t the u joint or flex plate have failed by now? Appreciate you responding earlier. Bb

U-joint yes but a cracked flex plate can last for many years. The flex plate should not be too hard to check.