transmission fluid

I do Mine ONCE a year......80,000 miles

It all depends on your application, If your Doing Highway Miles with lightweight Freight..You can probably go Further

 

ran my last truck 7 years never changed it checked it now an the never had a problem

 

Interesting this thread exist. I was discussing this exact same thing today with a fellow driver friend of mine. He has a new truck, so things like this wont apply to him. I was saying to him that I think Im going to change all fluids every year. I have either 1,000,000 or 2,000,000 miles on her. The seller has no records and I cant find any history of this vehicle other than an out of frame rebuild at 75,000 miles. Yea, I dont get it either. Anyway, I''d rather be safe than sorry.
Do yall think Im being a little overzealous, and any recommendations?

 

Once a year probably isn't unreasonable. Just because gear oil doesn't turn black like engine oil doesn't mean it never wears out or becomes contaminated. That being said, I know of trucks that have been on the road for years without ever having rear end or transmission oils changed and no issues.

 

Once it all leaks out?
I worked at one shop, the only time gear oil got changed was when the diff got changed.