Packard Forum Index » Pre-War (1899-1942)

The late 1920s cars underwent tremendous developmental changes. For Packards, I'm guessing gear ratios were in the 4.5 to 5.0 range, giving them rather modest cursing speeds. I haven't been able to find the actual ratios and how they changed over those three series. Also, what were the engine compression ratios?

Thanks for the help.

Phil

Standard ratio is 4.69 to 1. Sports models were 4.38 to 1. In either case 50 mph is fine, 55 mph is pushing it and 60 mph sustained should be done only on the way to the engine rebuilders for new poured big ends. Compression ratio was 4.8 to 1 and quite high for the day. Peter T

Most shop manuals for cars year have the ratios listed usually several ratios depending on model or body styles.Possible to learn a lot by reading manual all you need is to remember what you have seen I retain less the older I get.

As you consider the effect of the rear axle ratio on rpm and road speed, don't forget to take into account the effective tire diameter.

Here's some PMCC data related to 19" tires driven thru the 4.38 and 4.69 ratio rear axles.

Attach file:

---

  rpm vs mph.jpg (112.05 KB)

Thanks to each of you for your responses. My car is a 5th Series coupe. I think it is quite sporty but I will guess that it has the 4.69 gear ratio. The “sport” designation was probably reserved for the roadsters and speedsters. Anyway, I think top road speed will be influenced more by ride and braking characteristics than engine rpm limitations.

My car has Stabilators rather than more modern hydraulic shocks. The stabilators provide a slightly springier feel to the ride than what I am used to. To my surprise, the combination of leaf springs and Stabilators makes the car handle speed bumps and potholes very well - better than a lot of modern cars. However, at speed, I am reminded that this is indeed an old car.

I have inspected the brakes and adjusted them to correct for a tendency to pull to the left. The linings show very little wear. The linings are of a woven design (see picture) which might be period-authentic, but which provides a very spongy brake pedal. I suspect using modern design brake lining material would greatly improve braking behavior.

Anyway, thanks again for the responses.

Phil

Attach file:

---

  lf brake.jpg (727.47 KB)

Modern brake linings will NOT improve your braking feel and will decrease your brake effectiveness. The cable and rod brakes on pre hydraulic systems always have a take-up play which is less noticeable with the early Thirties Vacuum boosted mechanical braking systems. Your woven linings are the best but are now totally illegal in Australia. Importing a vehicle with OEM asbestos parts is a nightmare and costs around 10k to 15k to get around. Your rear axle ratio can be checked by jacking one rear wheel up and rotating the wheel two revolutions whilst counting the tailshaft revolutions. If the tailshaft revs are over 4.5 then you have as 4.69 diff ratio. Peter T

Asbestos anything is about to formally go bye-bye in the US shortly as well.

I have always been of the idea that going to a higher gear ratio (lower numerically) in a pre-war vintage car would be to slow the engine speed for a more comfortable drive and less wear and tear on the engine. I know in later model cars some change to a "high speed" ratio for higher speeds, but pre-war vintage Packards were not made for this use.

IMHO fitting a higher diff ratio is a bit of a trade off in an older car as you do not generally have the horsepower to drive a higher ratio particularly in hilly country. The 5th Series Six has approx 85 hp gross which is probably 45 at the wheels. I have fitted a 4.38 ratio to my 7 pass 304 bodied 533 and with a trailer of old bikes attached it will sit on 50 mph comfortably and takes most hills in top gear. It would probably not pull with a 4.1 ratio. Peter Toet

Attach file:

---

  1927 Packard & Trailer - Copy.JPG (81.90 KB)

Good point, Peter. The engine will not develop enough power if the gear ratio is too high. This would necessitate shifting gears more often.