i have a 3 speed it makes ur car a lot faster on a really long straight away u can adjust the gearing so it shifts into 3rd a bit faster and it is a bitch to install u have to take out the old tranny and to do that it takes a while it took me even longer cause i have reverse also i had to take apart my 3 speed and 2 speed and put the old revere module into the new 3 speed that suxed it was worth it and it was fun all at the same time rc is all about having fun and experimenting.