Transmission oil change due to time?

map40 wrote:

et2 wrote:
I'm always wondering why people don't just follow the instructions in the owners manual. Even if you don't have one they can be gotten on the web by searching.

Simply because some of us know better.
You wonder if I believe I know better than the group of engineers that designed the best transmission in the world? I don’t. I just know better than the clown who writes the manual.
Once when we were discussing what oil to use for the V10 engine of the Viper I spent some time with the developers of Mobil 1. One of them told me “oil weight, brand, conventional or synthetic, all can be mixed” I thought he was just talking out of his a** until another one of them told me he was the most knowledgeable guy in engine oil in their company. I asked him later to explain and he told me that oil weight mathematically averages. Dino or synthetic can mix because they are both oils, and that changing the oil every 3000 miles was the worst idea ever as it will produce more wear than running the same oil 6000 miles.
I later asked around the company and found out that mileage and time maintenance intervals are decided by engineering, purchasing AND marketing. So does tire size and brand.
Keep that in mind the next time you read the maintenance manual...

Map40

I have to agree with you more or less on your post here

i.e. the meritor rear end folks want me to change the differential oil every year with conventional oil and three years with synthetic. With the little miles I drive I think that is over kill but as a risk management tool I have an extended warranty, Good Sam ESP, that requires the manufactures maintenance schedule to be followed.

JimR