After several adventures with differential rebuilding and tracking
down historical information in various parts of the world, I can
categorically state the following:
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.
--
"Entropy Happens!"
Michael D. Miles, PE Consulting Design Engineer
(503) 292-1234, FAX: (503) 292-1105
email: mdmiles@mdmpe.com
http://www.mdmpe.com/
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