ARB locker and diff ratio

[James W]

My rear diff is now not only making a whine but now a knock-knock-knock sound. 8 months ago it got water and sand in it and now the borrowed time is about up.

To replace it I need to determine the ratio.
The question is if I jack up one wheel and count wheel rotations vs drive shaft is this half or twice the ratio because only one wheel is rotating. I think it's half? Can any confirm for me?

Secondly with a new diff or maybe a LSD priced at $NZ600 maybe I should go a little more and look at an ARB locker. The thinking being if the gear carrier is duff in my existing diff the ARB replaces it all anyway.
So is it likely to be the ARB RD07 to fit the rear of an 1991 Isuzu MU. Has anyone done one and help me confirm my diff and whats required?

Anyone got an ARB locker lying around or know of a sweet deal?

And no I don't want an lockrite etc as I do want it to be driver selectable.

[mudgrip4]

When I had my bighorn on the dyno with Blackwood Mtrs, the computer automatically assessed the diff ratio - I think it was 4.18 for mine. One way to assess if nothing else presents itself. Costs about$100 and for an extra $50-60 you get the injection timing and fuel advanced as well. Just a thought - Mike.

[geeves]

Before buying anything I would be looking iside the diff and working out what is worn Knock knock knock sounds more like bearings and if the crown wheel or pinion is worn the locker idea wont fix it. At the same time count the teeth on the cogs This will be more accurate although your method works on open diffs ie count the turns and divide by 2

[geeves]

Also I know how water gets in but sand?

[Yarno]

Oh sounds like your diff is no good... water has got in there and worn your bearinigs thus maybe (proabable) worn your gears.

The gears should be 4.56 ratio as you have the 2.8 td.

The RD07 locker is for the DANA diff in the american made truck (fronteara and rodeo) not MU or wizard.

I put the RD 44 locker in mine as this is the correct one for the 12 bolt Isuzu rear which you will have.....

Hope this helps

[James W]

Part of my reasoning is that it's my daily driver, so a diff swap is more appealing in that in can swaped out and keep driving. If any bearings are duff it would be a day or two of repairs, ordering parts etc. It is an unknown.
An ARB locker may solve some of the problems but correct, not all, and I won't know untill I pull it out.
How did sand get in there? I don't know. I supect the front seal is worn as it weaps a little oil. That and it was submerged deep a couple times. I have breathers fitted.

Yarno - the RD44 locker, thanks. The locker listing I was looking at didn't quite sound right