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What weight oil should I use for transmission and overdrive. How much oil is the correct amount.

Many of us have had totally satisfactory results with 85W-140 GL-1 gear oil. Correct level is when the oil is at the hole about mid-way up on the transmission and overdrive cases. The holes have a ⅜" NPT plug with a square head, like the drain plugs.

In 48 it is possible you have the R9 or the mid year replacement R11 unit. You didn't mention which unit you have but I believe the procedure and lube recommendations is the same for both.

In addition to the lube recommendation JWL mentions, here is a bit from one of the service manuals on the fill and subsequent checking procedure. The plugged fill holes on the trans and OD units are at slightly different heights. If you don't follow the recommendations, then after a period of service when it is time for the check oil will appear to be low in one unit and overfilled and will run out the opened hole in the other.

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Packwagon

I found the capacity information is in the tune-up manual (likely others); it is 2 pints for the transmission, and 1.25 pints for the overdrive.

dp