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I would suggest that you do not change from 4.1 to 3.9 unless all of your travels are on the plains of America. Your 4.1 when put into overdrive is 28.7% overdrive and the difference in conversion to 3.9 will be less than 100 rpm. If you convert to the 3.9 before overdrive, you risk being a bit more overdriven on reasonable hill climbs and you will be "kicking out" of OD more often. I have learned from bitter experience that perhaps the Packard engineers knew their Onions. Damaged axle shaft change...yes....Diff ratio change from 4.1 to 3.9 ...very debateable. But it is your car ..so whatever you want is of course approved. Best Regards from Down Under where my locality has just enjoyed ( endured?) its' first week of over 100F for 125 years. My Packards did not overheat in this...phew!. PT

Thanks for the opinion Peter. It's something I am considering for better 4 lane rpm's. One person here has already done this and as far as my knowledge, has had no ill effects due to the change. Now as OD pointed out about damaging the taper by using the drum to remove the axle. I have access to a lathe and have the drills and taps required to make an adapter for my slide hammer, I thought about it, and decided to, and have already made the adapter for that very reason. Still working on the pinion seal also. If anyone has replaced it, please chime in. I will post what I find/ end up doing here and in the parts interchange.

Thanks OD.

Regards, Steve

To remove my axles, I just put the axle nut back on the end of the shaft, caught the backside of the nut with a hook on the slide hammer. One slide and the axle came right out. Simple.

I bought a coupling nut and a 2' length of threaded rod the same size as the axle thread -- 7/8-14 in my case. I wanted some way to be able to lift and maneuver the axle to avoid the chance of pulling it over the seal. Used the threaded rod for the purpose and the extra length and leverage worked nicely. If my slide hammer were a bit more rugged that would have worked too.

Was going to cut and thread a short piece off the rod for the slide hammer but decided threading the head of a bolt was easier to get in and out of the coupling nut. After the first axle experience, made the seal puller and the second axle was a piece of cake.

Big Kev (and others): if the outer bearing race came out very easily, you may want to take some steps to make it a snugger fit before reinstalling so you avoid the possibility of the race rotating within the axle housing - the race is much harder than the housing and you run the risk of wearing the bore in axle housing. The fit of the race should be a pretty snug fit, enough so that it takes some effort with a hammer and drift to drive it in. DO NOT use Locktite or similar as once it sets it will prevent you from seating the races against the backing plate when checking and adjusting the shaft end play. If the race is too lose, good practice is to take a center punch and create some stipling in a full circle within the axle housing where the race will sit.

My race did seat snug on reassemble and I did not grease the outer edge of the race or the axle bore, so it's a dry, bare metal contact between the two.

Here is the page from my blog on the subject:

https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=20952#forumpost20952

Does anybody know what the correct thickness of gasket is to seal the carrier to the housing? I want to make sure the carrier is in the right spot to re-install my axles.

As far as the pinion seal, it is a two piece set up. There is a carrier that the actual seal goes in, then that is pressed in to the housing. The original number on the seal, stamped in the casing is 50066. It is a National seal. I have called a local seal house and it crosses in to a Chicago Rawhide number of 16117. Dimensionally it will fit the carrier and has the correct ID for the pinion shaft. I have ordered two of these, and as soon as I have them and can verify that they fit and work properly, I will come back here and confirm and also put it in the cross reference chart. I will also post some pictures.

Back to your question in post #28, while it's true that a thicker or thinner gasket than the original will change the penetration of the carrier into the housing and thus can alter the position of the spider gears relative to the axle splines, I'd think that the length of the axle shafts plus the tolerance in the splines etc. would only make it potentially problematic if the gasket were grossly too thick. I don't have a used gasket to measure (perhaps someone else will) but the two surfaces are finely machined so I'd think a relatively thin paper gasket (with shellac or Permatex) would be fine, perhaps in the order of 0.010" - 0.025" or so conventional gasket paper.