I put in my Ireland Engineering upper mount first and instantly felt the difference. When I put the lower one in a few days later, I hardly noticed a change. I then recently just removed the upper mount and still have the lower in. Again, I didn't notice much change from when the upper was in. This would leave me to believe that it doesn't matter which one you put in, either or will knock down the engine slop and give you better feel. I never had a trans mount though.