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Changing diff ratio?

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Currently the diff in the xb is a lsd, 3.23:1 drum brake out of a xf ute. I have the original diff floating around with 2.92 gears  but is not lsd. My question, is it possible to get away with just swapping the 2.92 crown and pinion gears onto the lsd head? The 3.23 is great off the mark, but pretty not very good at 100kms. Now that ive changed it back to an auto, i can get away with fluffing round the final drive ratios a bit without running the risk of giving a clutch a hard time 

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yeah they should be the same diff. 25 spline axles 

you'd be easier to fit the LSD center to the 2.92 XB diff gears and reusing the XB diff.. this is because its a big stuff around to swap the pinions over on the diff.

 

However, ford did annoying things and you won't know until pulling them down.. but i think the bolt holes might be different(metric to imperial sized potentially) might be left hand thread on them also on old/new .. can't remember really but @gerg may have a better memory 

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My diff came out of an XG and all the old gear swapped over, but spot-on Dean about the annoying parts randomness of Aussie BW diffs.

My original diff build had a 25-spline LSD centre out of an EA, put into said XG housing that originally came with 28-spline open centre and axles. I had 3.27 gears but felt they were too short, so late went over to 3.08s when I had to replace the centre with one from an XD. I'd made a mistake when assembling the first build by shimming out the clutches too much, and the bolts broke that hold the halves of centre together. They came out and one got caught in a couple of gear teeth and bang! Still drove fine, but the centre was mangled from having no bolts holding it together. Only the carrier bearings were holding the diff centre halves together. It wasn't pretty.

So the current setup has an XG disc brake housing, 25-spline 2-pinion LSD centre from an XD, and Commodore 3.08 gears. This is behind a 302 so the pissy axles are what I always think about when tempted to launch hard.

Being XF, yours should have the same internals as XB. So I'll say a tentative "yes" to them being interchangeable. The usual setup with shims and preload needs to happen though, don't fuss hugely about tooth pattern, just as long as your coasting contact patch is ok and backlash isn't way out (aim for less than 10 thou at the crown). The drive contact pattern matters less because that will lap in over time.

You really need a diff housing spreader if doing the carrier bearing preload properly. If you've got fresh carrier bearings, you need preload on them otherwise they will wear out quickly once you put power through them. If you can slide the carrier in without spreading the housing, you have no preload. Some like to get the preload close, and hammer the shims into place but that just knocks the crap out of them and that's the reason why good ones are hard to find now (diff bloke told me that).

Do it once, do it right.

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yup i played swap de swap on gears for years (hey good poetry there)go the 2.92 and just leave it,some older diffs like valiant had some variations in 2.92 ,falcons too.

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yup i played swap de swap on gears for years (hey good poetry there)go the 2.92 and just leave it,some older diffs like valiant had some variations in 2.92 ,falcons too.
2.92s are apparently getting harder to find now, as everyone used to just chuck them when upgrading to 3.45s, etc.

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Thanx everyone. Will get into it some stage soon and see how it goes. I know the diffs not in particularly good shape. And from memory, my warrant man actually laughed at the amount of back lash it has haha. It doesnt really work as an lsd anymore. The end plan is to swap it out for an xh/xg xr8 diff so i get the disc brakes and, from what ive heard, 4 spider lsd. Gonna have to address the pinion seal too coz it leaves a puddle evey time it moves.

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Thanx everyone. Will get into it some stage soon and see how it goes. I know the diffs not in particularly good shape. And from memory, my warrant man actually laughed at the amount of back lash it has haha. It doesnt really work as an lsd anymore. The end plan is to swap it out for an xh/xg xr8 diff so i get the disc brakes and, from what ive heard, 4 spider lsd. Gonna have to address the pinion seal too coz it leaves a puddle evey time it moves.

The halves of the hemisphere can be machined internally a bit to allow cone engagement again, what happens is the tapered friction surface wears in the housing and the cones sit deeper and deeper into the taper as it wears.

 

 

Eventually they bottom out on the internal face (where the axle comes through), which prevents the cones from biting in the taper. Machining this flat internal surface a couple of mm will allow the cones to bite again, but now the spider gears (which rely on the cone depth to set backlash) now need to be shimmed up by the amount that you machined off the housing, so that backlash is back up to spec. I think mine needed 20 thou machining and shimming each side. You'd be surprised at how much difference there is with a 5 thou shim.

 

Where I stuffed up first time round, I actually shimmed the cones up too much, and when I put the two halves together, the spider gears bottomed out on each other before the housings touched. That's right, the hemisphere faces actually didn't meet, the two were held apart by the spider gears!

 

So I bolted it all together and thought "jeez this limo is tight" but it was because it was all bound together and the spider gears could barely move, and the two halves were driving purely on the 8 little bolts. They all broke off eventually, and carnage ensued.

 

So next time I did one, I made sure that the spider gears had backlash with the halves butted together. So far, so good. The limo's nice and tight too, but actually works.

 

There's either a build thread on it somewhere or it's buried in my gergwagon thread.

 

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The halves of the hemisphere can be machined internally a bit to allow cone engagement again, what happens is the tapered friction surface wears in the housing and the cones sit deeper and deeper into the taper as it wears. 
 
Eventually they bottom out on the internal face (where the axle comes through), which prevents the cones from biting in the taper. Machining this flat internal surface a couple of mm will allow the cones to bite again, but now the spider gears (which rely on the cone depth to set backlash) now need to be shimmed up by the amount that you machined off the housing, so that backlash is back up to spec. I think mine needed 20 thou machining and shimming each side. You'd be surprised at how much difference there is with a 5 thou shim.
 
Where I stuffed up first time round, I actually shimmed the cones up too much, and when I put the two halves together, the spider gears bottomed out on each other before the housings touched. That's right, the hemisphere faces actually didn't meet, the two were held apart by the spider gears!
 
So I bolted it all together and thought "jeez this limo is tight" but it was because it was all bound together and the spider gears could barely move, and the two halves were driving purely on the 8 little bolts. They all broke off eventually, and carnage ensued.
 
So next time I did one, I made sure that the spider gears had backlash with the halves butted together. So far, so good. The limo's nice and tight too, but actually works.
 
There's either a build thread on it somewhere or it's buried in my gergwagon thread.
 
Sent from my CPH1920 using Tapatalk
 
 
 
 
 
I usually machine the face off the cones and add the amount I took off the cones to the shims

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I usually machine the face off the cones and add the amount I took off the cones to the shims
Yeah I looked at that and thought they'd be as hard as a dog's forehead, also hard to grip in the chuck. Unless there's an easier way of grabbing them?

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Yeah I looked at that and thought they'd be as hard as a dog's forehead, also hard to grip in the chuck. Unless there's an easier way of grabbing them?

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Easiest way to grab them in the chuck is face them back to back and clamp them both in the chuck at the same time, they machine pretty nicely

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Easiest way to grab them in the chuck is face them back to back and clamp them both in the chuck at the same time, they machine pretty nicely
Ok that makes sense, use one as a spacer against the face of the chuck, makes it easier to true it up

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