Hi
My question is, if the differential fluid change is really necessary on a cargo van. For example I have a Chevy van with over 500k and I never change the fluid ,no problem.
Usually, when people say "no problem", what that
really means, whether they realize it or not, is, "hasn't yet blown up or otherwise died."
There may be all manner of problems that just haven't manifested themselves to those unaware of them.
Of course it's necessary to change the differential fluid, if you want the gear box to last as long a it can, and if you want to reduce heat, vibration and friction, all of which affect fuel economy.
The differential is the gear box, where gear meets gear to transfer the lengthwise flow of power from the engine through the clutches, transmissions, and propeller shafts into a right-angle direction. Proper differential fluid levels will reduce friction and wear and reduce shock and vibration. The differential gears are submersed in differential fluid to protect the moving metal surfaces from friction and wear. Normal driving subjects the fluid to high temperatures which eventually break down the fluid. Extreme driving, like towing or hauling heavy loads, only increases the heat and friction. The result is metal to metal contact and extremely high heat that eventually prevents gears from turning the car's wheels. You really don't want to wait that long, until the gears can no longer turn the car's wheels, before you label it as "a problem".
The vehicle's manufacturer recommends the interval for rear end gear oil changes, and it's usually found in the owner's manual. For a lot of vehicles the recommended interval is 30,000 miles. For others it's 50,000 miles or more. For the Sprinter it's 120,000. I usually change mine in the Sprinter around 80,000 miles.
One thing to keep in mind is, there isn't a single lubricating or hydraulic fluid on a vehicle that doesn't need to be changed out or replenished at some regular interval, being it engine oil, power steering fluid, transmission or gear oil, brake fluid, bearing grease (wheels, pulleys), you name it.
