Packard Forum Index » Pre-War (1899-1942)

enegine are different, but would these from a 633 fit on a 640

You need a copy of the parts book to answer these type of questions, its readily available as a reprint. It covers all Packard Eights from 136 through to 645 Each part number is listed with its relevant model. Absolutely invaluable to anyone restoring on of these cars even if only for the illustrations. The Service book is also available as a reprint and it is not much use!

If by diff you mean the whole rear axle assembly it is not the same although some parts are interchangeable. The ring gear and pinion are not interchangeable.
The front axles are the same, part # 157762
The parts book lists a steering pillar, # 132138 which I guess is the column. It is interchangeable