75-90w ok for all gears?

How often in miles do you change gear oils given little or no towing? 30k 50k 100k?
What do you use to change your transmission, rear & front differential, transfer case? Do you use basic 75-90w gear oil or do you upgrade to synthetic? I think my rear diff calls for a LT oil that is different from the others. Does it really matter if one doesnt tow too much? Thanks

 

I use Mobil 1 75/90 in my front and rear diffs. Zero towing

 

Amsoil severe gear 75-90

 

+1 to this, in the transmission, transfer case, and both diffs.

 

I think the maintenance manual calls for 30k mile intervals on diffs and transfer. Then states to change more often in severe driving and towing. I think its the same for manual tranny. Auto use to be around 100k, but I think that has changed to around 60k.

 

^^ This ^^

I also use the same in the T-Case. All get changed every 30K miles.