The left one with black cover, I have indicated the axle with red circle. Do you have any of them?
Can you tell me which bearing is the best?I don't even know which "Application" and "Manufacturer" I should choose.
ORIGINAL: sevoblast
Which transmission? The one on the right is the Type 1, and parts have not been available for some time now. On the left, looks like a Type 3, for which parts may or may not be had. Tamiya discontinued the overhaul kits for the transmissions a year or more ago, and more's the pity for that little move.
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.