every 50,000 miles
30,000
The differential fluid on a Dodge Ram 1500 4x4 needs to be changed every 50,000 miles for normal highway driving. If the vehicle is used in 4x4 regularly, then change the differential fluid about every 25,000 to 30,000 miles.
Refer to owners manual, it will give you mileage frames on when to change fluids.
There is no concrete answer. Different vehicles have different needs. For instance, an off-road vehicle may need a differential fluid change as often as every 30,000 miles. A vehicle used for everyday travel may never need a differential fluid change. Some manufactures consider the differential lubed for life and others recommend that it be changed at a set mileage like 100,000 miles. Refer to your owner's manual for when or if yours should be changed.
Nissan Maintenance recommends every 60,000 miles or every 48 months.
At 18000 miles if towing
every 30,000 miles or when fluid is dark brown depending on your driving habits, highway or city miles determine time and mileage.
Valvoline recomends 15,000-30,000 depending on how hard the vehicle is used...I do mine about every 30,000
When refering to "service" I assume you mean fluid change and/or check. I check my fluid every oil change and change my fluid twice a year. Granted i use mine very hard offroad. I also prefer running synthetic fluid, but check with a dealership and make sure yours doesn't take a special lubricant.
Generally every 30000 miles unless you have synthetic fluid, and the transfer case as well.
once a year
How often do you change the transmission fluid in a mercedes benz c240