I`ve got a top loader in my 63 1/2 Galaxie 427 . Tranny became hard to shift after about 15 to 20 minutes street driving and difficult to get into first at a light . I had changed
oil a while back and had to use the GL4/GL5 that is supposed to be ok ( could`t find any GL4
oil ) . Guess what ? It isn`t the same . A top loader needs a true GL4 . The GL5 has a higher sulphur content than the GL4 and can/will damage the brass synchos , causing hard shifting . Finally found a true GL4
oil at NAPA and will be changing it out shortly .