transmission/overdrive oil for R-9

Posted by West Peterson On 2008/3/28 9:12:31

My search abilities failed to bring up the answer I'm looking for, but perhaps I just didn't type in the correct word sequence, I don't know...
If this question is redundant, I apologize.
I've also posted my question on the AACA Forum, so again, if anyone finds that offensive/redundant/obnoxious, I'm sorry.

A service procedure recommended by Packard in 1940 suggested putting in 250 weight oil in my transmission/overdrive as a first step to try and eliminate some rattling noises that appear at a certain speed.

When I serviced the car after 40 years of storage, the oil I put in was about 80 weight, which I'm sure is sufficient for lubrication purposes. However, I'm hearing what I think is the rattling noise mentioned in the service letter. My thought is to find as thick of an oil as I can, put it in, and see if the sound changes tone or is eliminated. If the sound does not change, I should be able to conclude that the rattling noise is coming from something else (driveshaft, possibly being unbalanced and causing vibration elsewhere).
My question is, where do I find 250 weight oil, or something close to it?