<html><head></head><body><div class="yahoo-style-wrap" style="font-family:times new roman, new york, times, serif;font-size:16px;"><div dir="ltr" data-setdir="false">I know all the manuals say to use 20w-50 motor oil for the transmission. Most of those manuals were written back when Castrol GTX 20W-50 was formulated differently. Does the new lower ZDDP content make a difference in the transmission? I have a regular 4-speed trans in my 69 GT. The car is new to me and I would like to start from scratch with all the fluids in the car. Probably not a good idea to even get into what engine oil to use.</div><div dir="ltr" data-setdir="false">Mike MacLean<br></div></div></body></html>