The gear oil that many of us use in standard transmissions and overdrives, steering gear boxes and differentials, as previously noted, is SAE EP 85W-140. If your trans or OD makes noises with this, using a heavier oil is probably just forestalling the inevitable failure and probably further damage will result -- best to find the source of the problem sooner rather than later.

Just looking at the pictures in the 48-54 and the 55/56 parts manuals, it appears that the front crossmember pictured in Kev's 54 isn't used in the 55/56. Too cold to go out in the garage and crawl under the 56 to confirm but it would appear that the 51-56 frames are not all the same in this regard.

Just a comment about the king pin job. Best shop practice is to never use an abrasive hone to resize a bronze (or other) bushing; scrub and clean as best you can but particles of abrasive can and will become imbedded in the pores of the bronze and shorten the life of the fit. Always use a ream; you can buy an adjustable ream from most any machine shop supply house, and individual fixed size reams for various diamter kingpins show up at lots of flea markets, often for a $1 to $5 each.

The additive packages are no doubt proprietary with individual antifreeze formulators and there's no reason to think that all brands have chemically identical packages, but they're formulated to be acceptably the functional equivalent or nearly so. I use the word "package" because there are different metals which require protection from corrosion, cast iron, brass, copper, aluminum and tin/lead (solder) at a minumum and there is no wonder molecule that protects them all. The packages I looked at some years back contained a chemical compound like tolytriazole for copper and brass protection, and inorganic silicates for cast iron, plus other ingredients. Some of these substances (but not the ethylene glycol itself) have a transitory life.

I'd say that they "control" corrosion to acceptable levels but I doubt anyone in the business would ever say they make the solution "corrsion-proof". Dem's strong words.

BTW, my 56 Caribbean still has it's original radiator, clean as a whistle, and to my knowledge as never been serviced. So did my 34 Packard until a few years ago when I decided to recore it based on it's physical appearance, not its performance.

I don't know whether it's appropriate to recommend specific vendors on this website, but I can recommend Ed Strain down in Florida as a top notch rebuilder of Bendix TeadleVacs. He does hundreds per year and I have experience with perhaps a dozen he's done for friends of mine. You'll find his phone# in Hemmings in the Packard section. Like many rebuilders he has needed service parts manufactured for his own use, but not for sale individually.

Speaking as a retired chemist let me clarify what has been said about the effect of heat, use and/or age on the characteristics of ethylene glycol-based antifreeze. Neither age nor use nor temperature experience change the molecular structure of EG and hence they don't change the compound's freezing and boiling points, nor that of its mixtures with water. However the same can't be said for the additive packages which protect against corrosion and ethylene glycol in the absence of these additives can be quite corrosive to certain metals, these additives are actually consumed in the process of performing their tasks. Thus it's foolish and potentially expensive down the road to not change it at least every other year. While the same analogy doesn't hold for lubricants like gear oil, simple examination doesn't reveal the presence of condensed water vapor and particulates and again it's my recommendation that they be changed at regular intervals, though perhaps not the same intervals as were recommended for cars in every day service. I'd never return a used lubricant to service unless in the rare case that it was just changed previously and I had collected it in a clean container in order to effect some repair or service. The cost is so trivial compared to the consequences of damage. If we can't afford a couple of gallons of antifreeze and a couple of pints of gear oil, perhaps this isn't the hobby for us.

The other item pictured that you're calling a bolt is the access cover for adding gear oil.

Check your lubrication chart, but all the Packard steering gear boxes I'm familiar with take gear oil, not grease.

If you're not prepared to do the cross shaft per the proceedure outlined and are going to "guesstimate" it, better too loose than too tight or you'll run the risk of springing the box and doing internal damage.

I never knew that unit was called a Mag Nu Matic, you learn something all the time. Mine was rebuilt by McVey's about 8 years ago, and they did a fine job.

Incidentaly, I thought the electric component was just an electric solenoid to admit vacuum to pull the pump piston up; it's not an electric pump as I believe I read somewhere in this thread.