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The differential on our 48 Super 8 has a annoying whine. The noise has been consistant for several years. I thought the noise was caused by the non working overdrive transmission, but the transmission was changed and the whine is still there. I have the option of 3 different gear ratio differentials and would like advice which one would be the best exchange. The choices are 454, 390, 354. Thanks for your help. Packardtaximan

In overdrive, your effective final drive ratio will be 3.15, 2.81.and 2.54 for those three ratios. The 4.54 will give you unparalleled flexibility on back roads and in town, but is a bit busy on the highway. The 3.54 with overdrive will lag on steep hills, even on the interstate. That's the combo I had on my 50 Super in college days. 3.9 is probably the best compromise. 4.1 was the usual ratio with overdrive on those cars.

Thanks Ross, since this is my preferred road trip Packard I was thinking about upping the ratio for better mileage. The car gets an average of 16.5 MPG highway so I will go with the 3.9 ratio. Thanks again for your reply.

Packardtaximan

I have a 52 200 with a 327 and an ultramatic ,what ratio would go on that rear end ? the same 4.5 ,3.9,3.5 choises ?
Ive had luck with other fifties car projects making sure I put in the lowest ratio gear I could get to make the highway speeds and not blow the engine at the expence of going into low ration on the steep hils around me

You most likely have a 3.54 now, which should be stamped ever so lightly on the face of the diff carrier in between two bolts at the 11 o'clock position. That works OK and the car will cruise at 70 without too much fuss if your tires are as tall as possible.

It's time to start over and change differentials again. The one I put in has a severe growl when de-accelerating. It is quiet when under a load. The gears showed no signs of abnormal wear and it was nice and clean inside. I spun it over by hand on the work bench and it was smooth and quiet. Is there a way to check to see if they are good without putting them in a car and driving them under a load? I have a complete assembly that I am going to try next and if there is a way to check it before installation it would be a great help. Thanks. Packardtaximan

I have a complete assembly that I am going to try next and if there is a way to check it before installation it would be a great help.

Surely there is a way, and assuming no damage to the ring and pinion gear faces, you should be able to get a quiet rear axle. To do so, you check the bearings, pinion preload, backlash and tooth engagement and there is a specific sequence and technique to all this. But it's kind of specialized work so unless you're familiar with how to set up a ring and pinion and make the necessary adjustments, it's probably best to seek out someone who is. If you want to try it on your own, Motor's manuals of the era gave pretty good instructions on how to do this, and perhaps Ross can simplify it for you if you want to try it yourself.

Thanks Owen-Dyneto, If my next attempt fails I will seek professional help. I know only enough to get into trouble. I am the R&R type of do-it-yourself self taught tinkerer, not any form of mechanic. Packardtaximan

Dear Packardtaximan:

The original problem was most likely caused by too little pinion preload or improper pinion depth, but can also be caused by improper differential preload or a backlash problem.

Given the replacement is worse but load sensitive it too is probably a severe pinion problem.

If you want to do it yourself, the best path would be to sign up for a driveline course at an automotive tech institute. I was lucky and went to a GM technical center way back when they had lots of money. Finding a place shouldn't be very hard because the car companies treat highly qualified mechanics like shxt and the turnover is so high they have to have a program in every county. Although if you smoke cigarettes all day and take a lot of drugs they treat you pretty good.

The other choice is to take your original unit to a driveline shop, or a machine shop that does differentials.
They will check the preload and do a contact pattern and set the whole thing up for installation. You will have to do some searching and also give them a copy of the Packard manual. Not that there is anything special about the Packard unit, but the manual will let them see what family of methods to use.

Hope this helps.

If your unit is quiet when pulling and loud on decell then chances are excellent that the pinion nut has come loose. This is not remotely uncommon as our friend in South Africa had the same issue a week ago in another thread.

For a first whack, and without any special tools, I'd say lock on the handbrake and tighten the nut about as much as you can with one arm and a 12" wrench. Take it for a ride and see if it's better. If you like it, reach in with a punch and stake the daylights out of the nut. If it is merely some better, you could try making it a bit tighter. It is not as though you are going to hurt anything as the horse is already out of the barn.