My eb has a shirtload of "backlash" In the diff and at slow speeds this is a bit annoying as you can feel it take up and somewhat bunnyhop.
Now the diff is just the standard open center for the e series. It is not noisy and is in good condition besides this.
From my understanding I should be able to simply tighten the pinion nut untill the correct preload is met and this should be ok.
Or am I overlooking something.
(I won't be winding up the nut until the bearings are jammed up the races)

There is 2 ways of removing backlash....BUT....the contact print might not be right.
There is moving the pinion in and out, and moving the crownwheel/carrier left or right.
Easiest way out is to get a 2nd hand diff.
If the pinion nut is loose, then you have a rebuild on ya hands.

I see.
So do you think it would be worth trying to just tighten the pinion to remove sone off the backlash. I'd be able to tell then if it's the pinion that's out or the crown.
If it comes down to needing a rebuild of a 2nd handy I'll be getting a limo.
Is it common for the pinion nuts to come loose?

So you've checked the tailshaft uni's aren't adding to the backlash ??

You can get a pinchbar and a block of wood, and carefully check the fore/aft movement of the pinion, I wouldn't be tightening the pinion nut - once you collapse the spacer further, there's no going back. From memory, there is a torque you can apply to spinning the pinion for new and used bearings for preload.
I'd be taking off the back cover/hat and checking the heel/toe contact of the crownwheel to the pinion, and checking the backlash with a feeler gauge - doing it just by rotating axles, etc doesn't really give you a true picture as the planetary gears (whatever they're called), have a fair amount of backlash too.

I'd think the lateral adjustment of the crownwheel would be the only one you'd usually need to touch.

Grab a Ford shop manual, and have a read of the rear axle section - it is covered in good detail.

When i replaced my clutch i did the unis aswell.
I've replaces 3 or 4 lots of falcon diff bearing with my boss' dad (very good mechanic) at work so i should be right remembering how to check the internals.
Kinda wondering why I thought tightening the pinion would be a fix.
Might just leave it and get a 3:45 diff.
Anyone got a 3:45 diff suit eb? Haha

If the pinion nut is loose, tighten it up and see what happens, you can't hurt it.
But It normally means one of the pinions bearing has failed.
The collapsible spacer is only there to give you something to tighten the nut against. If it has come loose, either the nut really has come loose and tightening it will be all the needed + some thread locker. OR the bearings are worn which has taken out all the bearing preload.
Tightening it up will be a short term fix until you either rebuild the diff or replace it.
If it really is gear lash and it has not been there for the cars life then you have a gear wear problem.

You can't check the gear lash with a feeler gauge, you need a dial gauge and a magnetic base.

When I build extreme duty diffs, eg: drag racing or serious off road, I don't use a collapsible spacer.
I use a solid spacer that I will have custom made for each diff.
The collapsible spacer can let the pinion 'walk' up the crown under extreme load and this causes a few problems. the first is incorrect gear mating at the most critical time, which often results of broken gears. It also causes the pinion nut to come loose.

A solid spacer lets you properly tighten the pinion nut and stops gear walk. I used to only do it with the drag race 9 inch diffs because you can buy kit for it. Then A friend who crews on an Escort rally car was telling me about the diff failures EVERY rally. The nut would come loose every stage and they break gears almost every rally. We set it up with a solid spacer two years ago and it hasn't broken a gear yet and the pinion nut hasn't come loose.

Yeah, should've said DTI for gear lash - a lot easier.

If the crownwheel and pinion had teeth wear, I'd think you'd be hearing it - drive gear side particularly when under load, disappears on backing off.

If you do replace a crownwheel/pinion, you should replace them as a set, either new or used.

If you do have to undo/do up the pinion nut, you might as well replace the pinion seal while you're at it.

The diff is very quiet. No noise cornering, or coasting, underload. Nothing.
I will tighten it a see what happens just Cos it is so quiet hopefully pinion is loose.
I'm going to do the pinion seal and the extension housing bush and seal at the time.

Put the falc up after work.
pinion seal wasn't leaking so I didnt touch it.
Had a good feel of the diff feels like it could be in the sun gears.
Replaced the extension housing bush and seal, greased the tail shaft. And found out my right rear caliper has locked up in the handbrake mechanism, it was almost completely locked on, had to swing off the mechanism to release it.
On the drive home it seems to be alot less backlash. Maybe I was just feeling the heavy brake drag.?

So that's the pre EF handbrake ??

Yep, the fantastic prone to problem set up.

hi I have the same problem, get heaps of backlash from the diff once its heaten up, also rear brake caliper feels like its may be stuck, could I have this locked handbrake mechanism problem?