Transmission and gear oils can be contaminated with metals, solids, and moisture, and those contaminants should be removed before they can damage the system.
Conversely, a test of your ATF, manual transmission fluid, or gear oil may reveal that it's still in great condition, and you don't need to change it as early or as often as you thought.
We can tell you what condition the oil is in, whether it needs to be changed , and whether the unit has any pressing mechanical issues that should be taken care of.
Transmission and gear oil samples can be sent in the same sampling container as engine oil samples, and you can use the same oil slip too. The cost is the same as for engine oil.