I had a camaro window motor for a 4th gen and did the thermal strip delete repair then went to install it in my firebird and it fit BUT, when I tried the window it didnt roll down but 3". I eventually pulled it off to find the # of teeth on the gear were different than on my '93 TA. I dont recall what yr. the camaro motor was but it was a 4th gen. What gives? I thought they were all interchangeable as long as they were 4th gen.?