Hello I have a 1989 Jaguar XJS V12 I believe the trans is a GM hydramatic 400.I am having trouble with it shifting,It doesn?t shift from first to second unless I go 55mPH and the RPM?s get up to 5,000 and when it shifts it shifts hard,I noticed trans fluid in the Vacume line to Modulator on trans I changed the mod and it is still shifting hard at high rpms the fluid looks good nice and red no burnt smell and level is good does anyone know whats the problem thanks