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

I have a 1948 Super 8 sedan that has a annoying whine. I have replaced the non working overdrive transmission thinking that was the cause. There was no improvement on the noise level. It sure is nice to have a working overdrive. I have a differential out of a 1950 automatic I want to install. How can I determine the gear ratios of each? If the ratios are not the same how will it affect my speedometer reading? Thanks for a great site and your help.

Not 100% sure about '48, but I would think a Packard with OD installed would have a 4.1 up to a 4.55 rear end. The ultramatic rear end is probably a 3.54. If you can find a competent mechanic to examine the rear, he should be able to determine if it is worn and what is required to repair it.
I wouldn't install a 3.54 rearend. It may require a different universal joint and that would cause you other problems.

Another point about installing a 3.54 rear is that in overdrive, you will have a final drive of about 2.5 to 1. Had that in my 50 Super years ago and had to kick down on many hills. 4.1 or even 3.9 work OK, especially with the 327.

I have a 1948 2262 complete chassis (with stick trans) here if u want tot buy or trade me out of the axle. Not sure of it's compatibility with your super 8. I'm still learning the 22 series cars. I'm 30 miles west of Nashville Tn.

Rather than install another used unit, why not consider rebuilding your current differential. Often, especially if it hasn't run enough miles to damage the pinion and ring, new bearings and adjustment is all that's required, though unless you want to try it yourself, you'll want someone familiar with setting up the tooth contact to do that work.

I think a 3.54 with stick/OD would be a poor choice.

I'll agree with Owen. If the gears are good then about all that will be needed are bearings. That way when completed u know what u got. gOOD BEARINGS. Good gears. That's about all there is to it.

Personal preference here:
I prefer very long ration axles. Like a 2.99 or 3.11. ESPECIALY for long stroke slow turning engines like streight 8's. The long ratio coupled with the overdrive should give at least close to adequate for hi speed I'state operation of 65-70 mph.

Example: My 48 Chief is real easy to change final drive ratios. Stock from factory was 4.07. I changed sprocket to get 3.60. With a 4-1/2 stroke engine and a 3 speed trans it makes it much better for speeds above 55 mph.

It really needs something closer to a 3.11 ratio. I have no very low speed pulling problems with it at all. It's just not a dragster or rubber burner from a standing start. Normal Civilized operation of the bike at very low speeds and acceleration is most acceptable.

Axle ratio choices solely depend on how and where u want to drive them.

Is there a way to determine the gear ratio without disassembling and counting the teeth?

I have never done this but have heard/read if you jack up one rear wheel and watch how many turns the drive shaft takes for one turn of the wheel you can roughly determine the ratio. Mark the wheel and drive shaft locations, turn the wheel, watch how many times the drive shaft turns for one turn of the wheel, and divide that number by 2. Someone please check me on this.

(o{I}o)

The ratio is stamped on the pumpkin, but you will need a good wire brush to find it. Look at the circle of bolts that holds the pumpkin in the housing. Its usually near the ten or eleven o'clock position.