Whats my Diff Ratio?

Mark the prop with chalk, now push the car so the wheel does one complete revolution
while car is being pushed  count the number of times the prop turns
if you have a 3.54 ratio the prop will turn 3 1/2 times……3.5
if you have a 3.77 ratio the prop will turn just over 3 1/2 times.. 3.7 times
3.9 ratio will give you almost 4 turns on the prop….and so on
with axle off car:
Conventional diff, 1 wheel held,- driveshaft rev’s for 2 wheel rev’s = diff ratio, (because of spider/side gear function).
Locked diff, (both wheels turning), -driveshaft rev’s for 1 wheel rev = diff ratio.
Pinion Tooth – Crownwheel Tooth count 
9- 40= 4.44:1
8- 33= 4.125:1
9- 35= 3.889
9- 34= 3.777
11- 39= 3.54
Escort MkI:
Saloon
1100 Manual 3.9:1
1100 Automatic 4.125:1
1300 Man 3.77:1 post sept -70 3.9:1
1300 Auto 4.125:1 post sept -70 3.9:1
1300 GT 3.77:1 post sept -70 3.9:1
1300 E & Sport 3.9:1 post sept -70 3.9:1
RS1600 & Mexico 3.77:1
Estate
1100 Man 4.444:1 post sept -70 4.125:1
1100 Auto 4.444:1
1300 Man 4.125:1 post sept -70 3.9:1
1300 Auto 4.125:1 post sept -70 4.125:1
Van
1100 Man 4.444:1
1300 Man 4.125:1
1300 Auto 4.125:1

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