I ve picked up a new sound this past week and I believe its coming from the transmission only dose it when your pulling a load but just running down the road its ok no noise. When I first get started in the mornings it seems ok but once truck is warmed up then I hear it. I got under it when I got home today and transmission was hot to touch. I understand there going to run with some heat but how much is to much ? Seems like I work a week then fix a week anymore
What kind of transmission do you have. Is the sound only in one gear? Does it change when you load it and unload it? You need to check temperature with an infrared thermometer. Anything over 110 degrees F. is hot to your hand. I wouldn't think that any temperature is too hot until it causes oil to break down or thermal expansion enough to cause things to get tight. It used to be for us that a transmission wasn't broke in till the gears howled in high range.
John its a Eaton fuller roadranger 8 speed and it seems like you can hear it in the higher gears5,6,7,8 and you hear it when pulling not crusing or coasting.