I have a 1965 fastback mustang. It has a 302 in it along with a C4 transmission and 8inch rear axle. Im really not sure what my trouble is coming from. Whenenever i put it into drive or into reverse from neutral it seems to stall and then kick in. I had this problem before i put in a rebuilt transmission and ive also shanged the rear axle twice. I thought for sure this would fix it but I still have the problem. Its like the power builds up and then kicks in and its like a thud that can be felt. I thought it was play in the rear axle, but after changing it out twice im not so sure any more. any help would be greatly appreciated.