Looking through this site, I noticed that some people are using 75W140 for the rear if you are going to be towing, and some people are using 75W90
in both axles

Which is the better gear oil to use? I have a 10,000 lb camper?

Also, what should I use in my transfer case?

Thanks,

Gman03842
Greg LaCourse

75w9- in both, dont worrya bout it. Its what the owners manual recommends.

75w90 in both, don't worry about it. It's what the owners manual recommends.
Same here. Use a good name brand ATF in transfer case...