Misc. Rear End / Differential Info.

©By: Michael D. Miles, PE
or visit his web site

The following is based on several pieces of email between Michael and myself, trying to learn more about the rear ends in the Morgans.

Formatted for the Morgan Web page by John T. Blair

Last update: 05/28/2001

From: "Michael D. Miles, PE"
To: "John T. Blair"
Subject: Re: Altman & Newman change

I did indeed have diff problems and ended up getting new side and diff gears directly from Morgan Spares. The ring and pinion were ok (and those are what people can cross to the Dana 25/Studebaker). I still have the old gears and I intend to send them to SASCO to see if they can find a cross. The following is a summary of my explorations:

The 7HA/2 differential is NOT the same as any known Dana differentials.

The 7HA/2 diff does have a ring (crown) and pinion gearset that IS the same as the Dana model 25 differential (perhaps others but thats not confirmed).

The 7HA/2 side (axle) gears are remarkably similar to Dana 25 gears BUT they have different splines and are therefore not compatible (unless you choose to make new shafts).

Beyond that, you take your chances. What really surprised me is that there seems to be no compilation of data on what cars used what axles. I find it a stretch to think that Morgan was the only maker to use the 3HA/7HA axle/differential combination but thats the way it appears. Sort of like the fact that the input shaft to the Morgan Moss box has a different spline than the Jag Moss box but is otherwise the same...

I also found that the peculiar wear marks I found on the ring/crown are caused by the bearing for the pinion sitting in an oversized (worn) housing. A slight wobble of the pinion causes the tooth tips to scribe the teeth on the ring/crown in a strange way.

A local diff shop has a unique tool to raise the inner surface of the bearing bore (similar to an internal knurl) which reduces the wobble.

I have subsequently heard that the 7HA axle was used on an Aston Martin DB2 or 3 but that is unconfirmed.

I was surprised at how little I could find in asking so many people. Everything is "I think ...". I even hounded the current Dana axle company to see if they had any archive info or historical record. They don't care. One interesting tidbit is that Salisbury was actually an American company. Their web site includes the following text:

" The Salisbury Wheel Company was founded in Jamestown, New York, in 1901 when C.W. Salisbury, a key-maker and mender of umbrellas, patented an automobile wheel, then pooled his life savings with two colleagues, Scott Penfield and E.D. Sherman, and started manufacture. Salisbury's first customer was the E.R. Thomas company, maker of the Thomas Flyer. In 1905, the company started manufacturing front axles. Two years later rear axles were added to its product line.

Acquired by Spicer in 1919, Salisbury was moved to Toledo in 1929, closer to the center of the automotive industry. Salisbury axles became standard equipment in thousands of automotive vehicles. At the outbreak of World War II the light, Salisbury's rugged axles proved ideal for the Jeep. The Jeep proved so popular that in 1945 Salisbury had to build a new plant in Fort Wayne, Indiana. In 1970, the Salisbury Axle group was renamed the Spicer Axle Division. "

This was why I was so interested in whether a Jeep axle might be close enough. Went to a Jeep guy that took a look and said its close but not close enough to be of any use.

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