Thread: diff reco

Well I now have my new diff and the new diff centre looks to be in realy good condition.

How do I make sure that I have the correct ratio as the one currently in my car without taking it out?

I want to make sure that it is correct before I buy the new bearings.

Cheers

Matt

Originally Posted by Blknight.aus

make an alignment mark with a pen on a crownwheel tooth and the casing.

turn the drive flange untill the mark does one full rotation.

thats your ratio.

# turns of the pinion : turns of the crown wheel Near enough is good enough. IE

the 3.54:1 diff is refered to as 3.5:1 3.54:1 and 3.55:1 (according to some manufacturers who only deal with .05 increments)
the 4.11:1 is refered to as 4.1:1 4.11:1 and the 4:1 (by some people for whom near enough is truely good enough)

to check it while its in vehicle

jack up one wheel, turn the wheel 2 full turns and count the propshaft revolutions.

by the by
the 4.7:1 with the removable center is usually refered to as "the plasticine series diff"

Not really the ideal way, especially when you have the centre out

Count crown wheel teeth, count pinion teeth then simply divide the two numbers, that's how come you have 4.1:1 and 4.11:1 diff ratios, they are actually different tooth counts

For example the brand new factory locked centre for a HDJ78 on the bench here has 41 crown wheel teeth and 10 pinion teeth

41/10= 4.1 so the ratio is 4.1:1

3.54:1 and 3.55:1 are arguable as its simply whether rounded up or down, but a 3.5:1 is a different tooth count....not near enough