4:11 gears?

[tbuck]

I bought my truck used and am trying to figure out what gears I have.
When I'm cruising on the freeway, at 65mph my truck is running at 2200ish rpms.
What gears do I have on my truck?

Also, I am planning on switching my differential oil over to synthetic. How much oil do I need to order?

[Tractor]

3500 Crew Cab, 4x4, 65mph at 2200 rpm = 4:10 rear end. At 75mph it will be around 2500 rpm or so. If you have a owners manual it should tell you the amount of oil you will need. We changed our 4:10 over to synthetic some time ago, just don,t remember....
TRACTOR