Hummer 4×4 Off-Road Forums Thumbnail (350x164) | 960_by_540_image (960x164) | 1920_by_1080_image (1010x164) I have a 2010 H3. At what mileage is it recommended to change the automatic transmission and transfer case fluids? Is this even necessary? Leave A Reply I wouldn’t do it unless something happened to the Transmission or transfer case. Leave A Reply Leave a Reply Cancel reply Name * Email * Website Notify me of new posts by email.