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

Recently had the R11 O/D transmission installed in my 1940 120 Club Coupe. The car drives great with correct performance from the transmission. The only thing is when Allen Rich installed it and drove it, he felt the rear end, especially the pinion housing felt overly hot. He backed off the yolk nut to relieve shaft tension. He feels it's better. I don't think he feels comfortable yet. Driving the car at 55mph for 15 minutes still produces heat that won't allow you to hold your on the pinion housing continuously. Both Allen & I would like some feedback. Making a mountain out of a molehill?

It's normal for the axle gears to generate heat and to pick up ambient heat and engine heat. But that does sound excessive for a short drive at a reasonable speed. I don't know what a normal temperature rise would be under your driving circumstances. Regardless of the overdrive, the axle should be running the same speed as without overdrive, and at the same or less torque load. Too much or too little lubricant could contribute to excess heat. Dragging brakes will generate a lot of heat in a hurry, but I'd expect that to be concentrated in and near the brakes themselves, and not at the pinion shaft housing. Is there any chance that an exhaust leak is occurring near any part of the axle? Are both rear tires the same diameter, or very close to it? What is the ambient temperature?

"He backed off the yolk nut to relieve shaft tension"

You mean the pinion bearing pre-load is now loose? This is not good.

Any hum or whine while driving....before loosening the YOKE nut? (I hope there aren't any eggs in that diff)

Since it is apparently now messed up and if your car didn't originally have overdrive, may I suggest to use the opportunity to replace it with one that has the ratio used on cars with overdrive? You'll lose a little high-end but you'll also be amazed at the difference in take-off and around-town driving.

There is no noise. No issues with being less tight. Does anyone know what is a normal temp to expect? I will be using a infrared temp tester to get a good read.

I think that the point is that it's not supposed to be less tight which itself could generate heat. I would like to encourage you to read through the service manuals on the preset but also if the bearings are bad that could cause excessive heat. The manuals are all available here in the Literature Archive and if your specific year doesn't have the details, check a later year as the technology didn't change in any significant way if at all.

Was the drive shaft assembly taken apart for any reason? It's important that the splined yoke be assembled correctly. Improper assembly usually causes vibration, but it might contribute to pinion bearing issues.

Note:
One internet source indicates that a normal temperature range for an automotive rear axle is 150 to 200 F. High speeds and high ambient temperatures will result in higher running temperatures.

MRM, re: an above poster's admonishment to replace your ring and pinion with one coming with your overdrive car: No. Do not.

I long owned a '40 One-Twenty which left East Grand with a trucky enough 4.09 as did all non-OD 120s. We added overdrive, bringing final drive OD engaged from 3.14 to 2.95:1. Weight is the enemy. If your 282 tuned, your car will run like a scalded cat and still, as Bob Turnquist told me, "climb hills like a goat." Non-blown 1936-37 Cords, weighing as much and with no more power, left Auburn with 2.75:1 final gearing.
Most old cars are geared like tractors. The l a s t thing you want is to go backward. Your car will float on the freeway. You've got the best of both worlds as is.

Gentlemen - I do not claim to know much about drive train system. The mechanic that has been working with me is very knowledgeable on Packards but knows there are experts out there on rear end issues that may need to be called upon.
The only repairs to the rear end along with installation of the overdrive was to replace the pinion seal due to a leak that was there before. He originally tightened the yoke nut to 140 ft lbs. Upon the first drive is when he noticed the heat generating at the pinion housing that he thought was excessive (again based off his experience). So it was explained to me that there is a crush sleeve inside which looses its full function after the first time its tightened (from the factory). He is well aware that loosening the nut off could cause issues with noise and this was done a little at a time with test drives between to see if the heat issue improved. Also changed the lube to a GL4 SAE 140 which is what is called out on the manual.
What I don't know is if the heat issue was there prior to the change, my guess is it was. Which could explain why the rear end was leaking regularly. At this time there is no noise, hum, or any indication of a function problem. I will be driving the car about 20 miles at highway speeds on Saturday and I will be stopping periodically to register the temp.

One thing I can say in my limited experience with this car is the heat from the transmission and engine seemed more excessive that the rear end when I was under the car.

If anyone out there is driving their car at highway speeds for a period of time, and you have a temp gauge, please take a reading for me. I want to know what your axle reads.

thank you as always....