It is usually on the ID tag on the door jamb. Legally you can carry 20,000 on a single axle, 34,000 on a tandem all across the us. Some states allow more. So to calculate your actual allowable gross combination weight is add the allowable on your drive and the allowable on your trailer to the actual weight you get on your steering axle. When these trucks were built, 18k on a single axle and 32k on a tandem was the maximum in most states.
