Includes 18T 4th gear mainshaft & 26T 4th gear countershaft instead of stock 17/27 ratio. Stock 26/18 ratio is used in 87-90 XL models. L79-E84 XL model years are all equipped with a stock 27/17 tooth ratio. Provides a higher RPM in top gear for more close-ratio shifting. Race quality has been the Andrews standard for decades. Components you can trust. All are manufactured in the USA from the high alloy nickel steel, ground to precise dimensions, heat treated and shot peened for strength and durability.