Reply To: Long threatened Worm Gear axle rebuild

[Bob Jacobsen]

Hi Bill,

I replaced the worm drive in my 836 with a 1934 hypoid assembly a long time ago (factory authorized process), because the bronze worm wheel (what you call the bull gear) was replaced shortly before I got the car with a slightly off-pitch reproduction, and it burned itself up. I still have the entire worm gear assembly (backing-plate flange to backing-plate flange), less axles, and I think (cannot guarantee because I have not taken it apart lately-but it has been in inside storage) that the steel worm shaft is still OK.

Timken made several different ratio worm gear sets (2.78 to 4.57) for Pierce, Nash and Stutz, and my ’33 was 4.29. If yours is also 4.29 (it should be), or 4.43 (the same steel worm shaft is used in both ratios – the setup may be a bit different, but just set it for backlash of 0.010 to 0.018”), I may be able to help.

I also have copies of the original Timken blueprints for both gears (revision date 1971).

A gear-cutting company MAY be able to make a new worm gear from the prints, but to set up for one gear will probably be super expensive, and to accurately make the gear may be a problem (witness Phil Bray’s high-ratio hypoid projects). The shaft was forged, then cut, then hardened in three different zones to minimum Rockwell “B” 72 (soft) on the mounting threads, Rockwell “C” 20-30 (medium) on the splines, and Rockwell “C” 57

minimum (hard) on the worm gear portion.

You are welcome to my whole assembly free of charge if you can arrange for someone to pick it up (I am in CA). I am 70 and do not want to deal with the task of shipping it, or taking it apart again. In the past (15 years ago) I have used Dave’s Transport to reasonably transport large parts to and from different parts of the country, but don’t know if he is still in business. His number was 612-441-3769, but there are many guys that do the same thing.

Your bronze wheel looks pretty good from your picture, but a knowledgeable gear person should inspect it to be sure. And as you probably know, if there is too much wear on the drive side of the teeth, you can flip the gear around, so that the seldom-abused reverse side of the teeth now becomes the forward drive side, extending the life of the gear. You probably also know that you MUST use a non-sulfur-bearing lubricant (not the typical rear end lube), so the bronze wheel does not get attacked. This is the typical failure mode for the gearset – the steel wormshaft is almost always in great shape. It would help if you know the history of lubricants used in your gearset.

Hope this helps. Happy Holidays,

Bob Jacobsen