Robert C. Ackerson's Standard Catalog of 4x4s is the most accurate reference material I've found for 4x4 information. I have the older edition (1945 - 1993) and purchased the 1945-2000 edition to get more recent data. I was a little disappointed that there was not more information available on the 1999-2000 WJ Grand Cherokees. But the book is still one of my most valued 4x4 reference books. You will not find a better source of information concerning drivetrain components. I use it for engine and drivetrain swap data. I've checked much of the Jeep data with factory brochures and repair manuals and his data is accurate, unlike other authors. There is a lot of technical data packed in a very tight space! I highly recommend it to any automotive enthusiast. If you're a 4x4 type gear head, this is a must for your book shelf.