The biggest contributing factor to overdrive geartain failures was the crappy fluid we launched the overdrive transmissions with in 1988. When we went to ATF + 4 that was remedied. I believe late 1998/1999. Several of our TSB's also stated that fluid color or smell is NOT to be used to determine the condition of the fluid. Back in the old days it was a good indicator - overheated fluid stunk. Extra fluid to the OD can't hurt but the 48 launched in 2003 1/2 and exceeded the life bogie at max GVWR. Info straight from the Fuels and Lubricants Group at Chrysler.