ORIGINAL: sevoblast
Bearings, any sealed bearing of the proper size will work. Check out Boca Bearings, they'll have what you need. Check all 4 bearings, two in each trans. If they feel 'sandy' when they rotate, get new ones. It's and easy install. You do not need super razzle dazzle expensive bearings, as the final drive shaft rotates slowly. However, Boca has consistently good quality, so go with them would be my recommendation.
+1 I like to use rubber shielded bearings for at least the output shafts because they seal out dirt and debris better.