NEW (NOS) GENUINE GM HYDRA-MATIC / DELCO / GENERAL MOTORS AUTOMATIC TRANSMISSION FINAL DRIVE SUN GEAR PART # 8661020. FITS VARIOUS GM FRONT WHEEL DRIVE MODELS WITH TH440 TRANSMISSION. I DO NOT KNOW WHAT OTHER TERMINOLGY IS USED TO DESCRIBE THIS PART, IT IS AN INTERNAL AUTOMATIC TRANSMISSION PART, MOST LIKELY USED BY TRANSMISSION SHOPS ONLY. PLEASE IDENTIFY BY PART#. IF YOU DO NOT KNOW EXACTLY WHAT THIS PART IS / DOES & HAVE NOT VERIFIED IT BY THE PART #, THEN IT IS PROBABLY NOT WHAT YOU ARE LOOKING FOR.