I tryed to purchase a transmission filter for my 1990 GMC V2500 4x4. Apparently, this Suburban came with either a 3 or 4 speed tranny. Since I just bought it and have not driven it, I chose the 4 speed filter. However, I went out for a ride this afternoon (finally got it registered) and I could only count 3 speeds. Does anyone know for a fact what type of transmission I may have? I have a 5.7 engine on it. By the way, 5.7 ltr is equal to what....a 318, 350, etc?