4L80E Overdrive Planetary. Planet Gear #279740
4L80E Overdrive Planetary. This overdrive planetary assembly is redesigned with a billet steel drive plate to eliminate spline/housing failure in high horsepower and extreme applications. Fits 1991-2000. Top Hat is made from 4140 HTSR billet steel and is contoured to the planetary housing to eliminate any possibility of separation under load. 100% drop-in product. No core exchange required.