How hot does your rear differential get?

I am trying to narrow down my whine at highway speeds. I noticed that when in 4th gear getting on it up to highway speeds 55+ I have absolutely no whine. tranny is quiet as a mouse. As soon as you hit 5th gear (manual) it whines but in 4th no whine? I touched my differential as soon as I got to the house and it was too hot to hold your hand on it longer than a second which got me thinking, Is that too hot? Let me know what you guys think!

 

This is normal to a degree.

Change your tranny fluid if you're concerned about temp.

The input shaft bearing is a direct drive in 4th so any noise that is there from that bearing will go away. Mine does the same thing

 

when you let off the gas the whine is very minimal. It is only loud when your cruising with your foot on the gas. It doesn't matter how much you give it gas it doesn't get louder with speed its just a whine.

 

Vtrguy, does your tacom also have the same whine? Thanks!

 

I'm thinking input shaft bearing.. super cheap to replace, major pain in the ass to R&R...


EDIT: My bad, didn't notice you were talking about your diff, if thats where the noise is , like jasmine said prolly pinion bearing, i just went thru this