I have a 2000 Excursion V10. I put Redline D4 ATF in my transfer case 7 years ago and change it every 50K miles. Before, when I put it in 4x4, the transfer case would make a slight woo'ing noise since it was new. The same with my old suburban before that. When I put the Redline D4, in just the first mile it was so quiet I couldn't tell if it was in 4x4. Even now with 205K miles it still runs just as quiet. Redline is a little expensive, but in my opinion $22 over the course of 2-3 years is chump change. I highly recommend it.