Frank,
The rear overdrive section and the front transmission gears section are connected and use the same oil. Fill the rear overdrive section up to the fill hole, put the plug in and then immediately fill the front transmission gears section up and put the plug in and you will be assured both sections have the proper amount of oil. I have always used the 90 weight recommended in the manual and try not to go more than 15,000 miles between changes. It is pretty cheap at the auto parts store. I live in Southern California where we rarely see 32 degree weather. Experienced transmission rebuilders tell me I should use the lighter weight oils if I ever move to a cold climate, in order to avoid damaging the overdrive parts.
