Classic/Antique Car Repair: 1937 Packard 120 diff leak, oil stains, pinion seal

Question
Hello Mr. Benjamin,
You answered a question of mine last summer, and I found your response to be supremely helpful!  
I have another question for you about my 1937 Packard 120:  I have an annoying leak at the front of my differential housing, just behind the u-joint.  I am guessing I need a new pinion seal?  Is this a quick weekend project, or are there a lot of things that can complicate the job?  I realize that these cars tend to leak a bit, but I'd rather not have to worry about leaving nasty gear oil stains on someone's driveway. It will leave about a nickel sized stain only after a few minutes when it's been driven and then parked.  
Also, I need to replace the front springs on this car (one is cracked at the bottom), and was wondering what your recommended procedure was on removing them from the car and putting in the new coils.  Additionally, I have one sidemount, on the passenger side.  Will I need to get a stiffer coil for that side?
Thanks for your help.
Dennis F.


Answer
The pinion seal is probably the culprit, and this is a job you can do yourself, but you need to get the torque spec on the bolt that holds the companion flange on - it is probably  150 Ft Lbs, but since I don't have a shop manual for your year, that is only an educated guess.   When you have the driveshaft disconnected, and before you take the companion flange off, try putting side to side and up to down pressure on the flange, to see if there is any play in the pinion bearing.  Probably it is OK, but if there is play, that is what wiped out the pinion seal, and you need to have that taken care of soon.  That job is for a professional - as the pinion/ring gear mesh will be affected.  Joel Ray will have the pinion seal, I believe - you can contact him at packards1@aol.com.

As for the spring question, I believe both springs are the same, even with a single sidemount - but since I don't have a parts book that goes back that far, it is also a guess.  But common sense says that the sidemount assembly weighs less than the average driver, and we don't worry about that - the sidemount actually works toward balancing the car - I wouldn't worry about it.

The procedure for removing a spring requires a spring compressor, and can be a very dangerous job, if you are not somewhat familiar with the process.  If you have access to someone who has done this before on a heavy vehicle like this with coil springs (like a pickup truck of the 60s, say), get that shop to help you with the job.  They will have an adequate spring compressor, and experience in using it safely.

Good luck - these are great cars, and I'm always glad to help with what little I know about them.  My only pre-WWII Packard was a 12, a much different critter than the 120, but I have had the front end apart on my 47 Custom 8 passenger and I have a lot of respect for those springs!

Dick