Diff ratio

[Not Happy Jan]

How do you workout what the ratio's are in a diff?
Nick

[mcl1959]

Do you mean by looking at it or by testing it.
All Holden diffs except 3.89 have the ratio stamped on the flange where the Uni is bolted on.
So if there is nothing on the flange, it's a 3.89:1 ratio.
You can test it manually (fairly roughly) by counting number of turns of axle compared to tailshaft. Ie, turn the tailshaft around 10 times and count how many times the axle turns. Divide your answer by 10.

Ken

[FCRB26]

 3.89 will have a Key way and 4 bolts holding the tailshaft on
3.55 3.36 have all short nuts and bolts the whole way around
2.78 and 3.08 have a long drain bolt and the next bolt up is a long one too.

And like ken said its written on the dust cover and the pinion wheel.

[Errol62]

Count the number of teeth and divide crown wheel by pinion.


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