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

The front joint is a Detroit ball & trunion joint. It functions as both a u-joint and a slip yoke. This type was widely used on Chrysler, Dodge, and Plymouth products for many years.

Roberts Motor Parts offers a rebuild kit for later Mopar applications. I have no idea what will or will not fit the Packard application. I've never encountered that type joint on a non-Mopar application.

Unless leaking profusely, and you need to change the pinion seal, don't touch that center pinion bolt. That is the rear half of U-joint that bolts to the differential. That has a very specific pre-load on it that you dont want to disturb unless absolutely required.

Really good to know, BigKev! Thanks for the heads up. I won't mess with it since it seems OK so far.

As far as differential fluid, what are you guys recommending and how often do you change it? I opened it up about 8 years ago and the stuff that came out smelled horrible! Can't recall what I replaced it with but thinking it could be time to do it again after 4K miles?

Hopefully you're aware that differential fluid is supposed to smell like a sulfur pit? It also won't get darker with age or use unless something is seriously wrong (engine oil does from carbon buildup).

Traditionally it was once a year to change it but it seems like most people pretty much never change it unless their cars are getting actual mileage.

I'm likewise curious to know what a reasonable time-based interval would be for the average enthusiast owner.

Diff fluid should be changed out at least every 100K miles. With our antiques, we're more concerned with condensation and sludge build up.
Best practice would be to flush diff housing with alcohol, not diesel or parts cleaner, because they leave a film on parts and the fresh diff lube doesn't bind to the parts as well. After flushing fill diff with straight 90w mineral hypoid gear lubricant or 85w-90 diff lube provided your differential doesn't have any bronze or brass shims or spacers in it. Most do not but very early units might. The extreme pressure additives break down the "yellow" metals. After 8 years, I would r&r the diff fluid. PB