Is My Dif 3:27 or 3:45 ??

[Grechie]

Hey guys

i currently have a 3:27LSD (or do i?) becuase so far all the people i talk to that have 3:27 sit inbetween 1900 and 2000 rpm in 5th at 100km/h, however , ive talked to other people with 3:45's and they sit on 2100rpm in 5th at 100km/h, and so do i, and my speedos not out i can gurantee u that, so, is there any real way of confirming, or is there someone out there that sits on 2100rpm in 5th on a 3:27?

[Tiga_EL]

Doesnt it actually say on the diff if u pull the wheel off?

[vino3o2]

I'd imagine tyre size would have a bit to do with it??

[5thFordWA]

First - have a look around the bolts on the backplate of the rear axle centre housing - look for a tag on one of the bolts - it may have the ratio stamped on it (or dont they have that any more?).

Or - jack up rear axle - use axle stands.
Chalk mark on tyre at 6 o'clock with something (eg a brick) next to the tyre to line up with that chalk mark.
Under the car - put a chalk mark on the tailshaft flange and a mark next to it on the diff housing to line up with that mark.

Now get someone to turn the wheel exactly one turn (slowly) and count the turns of the tailshaft.
If it goes about a quarter turn past the mark (3 1/4 turns) then its 3.27.
If it goes nearly half a turn past the mark (3 1/2 turns) then its 3.45.

Thats the only way to know for sure.

(This only works with LSD as both rear wheels are turning together - otherwise you need to turn both wheels one full turn at the same time)

No, its not an April Fools joke to get you under the car!

BTW, the difference between the two ratios (mathematically) is about 110 rpm at 2000 rpm - so you are on the right track.

Cheers.