Is it leaving oil spots on the ground when you park it? Rainbows on the ground coming from your rig when its raining? Oli change employees are well trained to cover their butts about any possible leak. Not sure if you are talking about the transfer case at the rear of the transmission or the front differential between the front wheels. If it is not dripping heavily or growling from worn bearings you can likely get lots of use out of it. Just do not run it low on fluid.