Dick:
I've seen various different stamp markings on diffs in addition to the basic
2 numbers, which represent the number of teeth on the crown wheel and
pinion - hence the ratio. The 'T' may have had some significance to the
manufacturing process, or the vehicle that the diff was installed into (eg.
Healey, Wolesley, Westminster, etc), or almost anything else! Maybe some
other lister could shed some light on this.
Your diffs' tooth count is the common one, the 3:91 ratio, used on all 3000
overdrive cars, and on 100-6 non-overdrive cars. The overdrive early cars
used the 4:1 ratio, and the later non-overdrive cars used the 3:545 ratio.
Bear in mind that the overdrive gearing changed from 28% in the 100-6 to 22%
in the 3000's, and that the speedometer gearing was adjusted accordingly as
necessary.
You don't indicate which model Healey you have, but it is probable that
unless someone has made some significant changes at some point, it is as it
was built. These days, many Healey owners do make gearing changes - eg: to
a 28% overdrive ratio in the later car, or to a 3:545 diff in an overdrive
car, or one that has a Smitty Toyota 5-speed conversion. It can be a bit
confusing!
Hope this at least partially answers your question. Any other information
you need, please don't hesitate.
Earl Kagna
Victoria, B.C.
BT7 tri-carb
BJ8
----- Original Message -----
From: "Lyle Matson" <medlabinc@msn.com>
To: "AustinHealey List" <healeys@autox.team.net>
Cc: "Dick Matson" <medlabinc@msn.com>
Sent: Monday, April 26, 2004 9:29 AM
Subject: Diff Ratio
04/26/2004
Greetings Listers:
I'm aware of three Austin Healey diff ratios:
a) 3:54 - stamped 11/39
b) 3:90 - stamped 11:4,
c) 4:11 - stamped 10/41.
I could be wrong about my own car but it seems low-geared. So this
weekend I got under there and found the stamp. The marking is 11/43 'T'.
What pray tell is this 11/43 'T' business. And what might this gearing
be useful for.
Dick / WA State
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