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How to determine Diff Ratio ?
a.j.stehr - 13/8/23 at 06:18 PM

Evening all,

I am trying to get my DigiDash+ set-up and one of the inputs is Diff Ratio. Given I bought the kit part built, 14 years ago, I am unsure of the Diff Ratio. It is Sierra running gear and the Diff (like the rest of the running gear) was purchased by the previous owner as re-manufactured directly from Ford (I seem the remember him mentioning it having an lower ratio?!). It there any way to work this out/tell?

Regards,

Ashley


adithorp - 13/8/23 at 07:11 PM

Diff ratio is the number of turns of the prop for one turn of the wheels.

Jack up one wheel.
Put a mark on the tyre and the ground and line them up.
Put another mark on the input flange and another on the diff lined up with it.
Now turn the wheel 20 turns while counting how many turns the flange turns.
Now divide the number of turns on the flange by 10 and you have your ratio.


You do 20 turns then divide by 10 because having only one wheel turning doubles the ratio.
Do multiple turns and then divide gives a better accuracy.


jacko - 17/8/23 at 05:56 PM

If your lucky there might be a aluminium tag on the diff saying the ratio
Jacko