A lot of people don’t check their transmission fluid regularly or don’t check it properly. Transmission fluid does not have to be changed as often as the engine oil does. Most manufacturers of imported trucks — Isuzu, UD, Mitsubishi, GM W-Series — recommend that for automatic transmissions, you change the transmission fluid in intervals around 25,000 miles. Please refer to your manufacturer’s specifications for the correct recommendation for your truck.
When checking the transmission fluid, it’s important to have the truck warm, in park and at an idling position for at least 15-20 minutes. It’s important not to check it on a cold engine. Raise the cab and secure it in place properly for safety. Pull the dipstick, wipe it properly, reinsert it and pull it out again to check the fluid level.
If you look at the fluid and it’s not a clear, red color and the consistency of warm maple syrup, you really should think about changing your fluid. If it’s dark or dark cherry or brown or black, you most definitely need to change it. It should not smell burnt when you pull the dipstick and smell it. The fluid line on the dipstick should be between the hash marks when you pull it with the truck running in idle. Good transmission fluid should look like this:
Most imported truck manufacturers recommend a Dexron or Mercon V fluid, but check your manufacturer’s specifications for the proper one.
Regularly changing your transmission fluid will prolong the life of your Isuzu npr box trucks, Isuzu diesel engines, Mitsubishi Fuso diesel engines, and UD diesel engines for mid range box trucks, GMC w3500, w4500 and w5500 and more.
For your convenience, we’ve made a video of Doug Busbee checking the transmission fluid in a Mitsubishi Fuso. For more information, please see our how-to video: