Packard Forum Index » Post-War (1946-54)

Finally found a number on the differential but it doesn't correlate to any of the numbers I had written down as possibilities.

The numbers I had all start with 90251, but the number on this differential is 443645, which isn't even close.

A Google Search didn't turn up anything.

Anyone have any ideas?

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If it's not a Packard part number then it's almost certainly a casting number.

443645 is the raw casting number for the carrier and cap assembly. The part number for the finished piece is often one digit different than the casting number.

Under Group 12.0015 in the 1951-54 parts list the number 443646 appears for all of the 1953 26th Series models so your differential is most likely from 1953.

The 90251x numbers are for a complete carrier assembly that includes all of the gears and is ready for installation. This number will not appear anywhere on the differential.

I've got a NOS 53 differential if you run into any issues....why do you have yours out ??

No problems (that I know of yet) - just doing a full frame off restoration on that Caribbean and was hoping to figure out what the gear ratio was. Trying to get the running gear sorted so it'll be a little easier to push the frame in and out of the garage. It's taken my main car's spot to be out of sight of the HOA (while the body and frame are seperate anyway) so whenever we have reports of hail I have to scramble to pull the frame out and stick the nice car in the garage before the attack comes.

Also on the plus side the rain has done an awesome job of knocking the dust off the frame from sitting while we finished up the Triumph. :D

....and was hoping to figure out what the gear ratio was

Some makes and models were stamped on the case or a tag on the case, always stamped on the gear set if you have access to it. The numbers on the ring and pinion are the respective # of teeth, just divide the smaller # into the larger. And of course there is the method of rotating the pinion and counting turns of a drive wheel and multiplying by 2.

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This was the case here, too - but the numbers weren't all lined up. I used a variation of your method - put some tape on the pinion straight up and down, and turned a drive wheel around twice and got just past 3 1/2, so I was guessing 3.54. As I was wirewheeling the differential down for paint, I found the stamped 3, 5, and 4 on the bottom, but they weren't super close together enough to be obvious. At least that answers the question!

3.54:1 was the standard ratio for Ultramatic equipped cars, it's really rare especially between 1950 and 1954 to find any other ratio.