I have a 99 Sierra and when cruising down the road at 40-45 mph and you apply a little gas, there is a moaning and can feel a ginding towards the front of the vehicle. The funny thing is, is that it only happens in that speed range. Any ideas?

 

I wish I could help...hope the mods don't get mad but check out The Diesel Place (just search for it, its a GM site)-they have techs on there that can answer that for you.