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Some help please - I need some schooling on banjo diffs.

I am potentially able to lay my hands on a banjo LSD centre. I'm interested in fitting this into the bog-stock diff housing on my FB sedan. I figure on getting the centre rebuilt (or at least checked over) before it goes in. From what I understand (and please correct me if I'm wrong), the LSD centre should (almost) be a bolt-in replacement for the grey motor banjo centre.

I figure that (just like all the other grey banjo centre upgrades) I will have to fit a red motor universal joint (Rare Spares UJ1004) to the FB tailshaft, and use the red motor U-bolts and nuts (Rare Spares UJK002) to mate up to the LSD.

I understand though that the grey diff has course splines, and that some of the later banjos were fine spline. Were the LSDs coarse or fine spline (or both)? Is there an easy way to check that the LSD is coarse (say by counting splines.. I'm guessing that the fine are 28 and the course are 10 splines?) before we go through the purchase-and-postage process?

Interesting that Harrop still make a TrueTrac LSD centre for 28-spline (fine spline) banjos https://www.harrop.com.au/shop/truetrac ... -28-spline ... need to bring a pretty hefty wallet though.

Cheers,
Harv

Fine spline Harv. HR's were listed with the same axles for both standard diff or LSD diff. The side gears are different but only due to the LSD cone that mates up to the gear. Standard side gear has a stepped shoulder whereas the LSD side gear is flat on its back side. Not sure of the number of teeth compared to early grey centre. You'll also need the usual 3/8" UNF long bolt to fit I'm guessing.
Interesting about the Harrop LSD centre. I'm assuming it will bolt up to early Ring gear and pinion set. You'd just need to fit fine spline axles from say EH. Been thinking about boat launching duties with my ute.....with extended drawbar of course!

I have an LSD centre and I am sure it is a coarse spline ????

I think the course spline banjo's were Torana I think, so its a possibility. I was only thinking HR LSD. Torana's don't usually enter my mind......what's left of it!

The LSD in my V8 SS Torana was course spline, I broke a few axles.
The LSD in my XU1 Torana was a fine spline. It never worked properly so I had it rebuilt.

Had a coarse spline 3.08 LSD centre under my EK sedan for years but that was in the EH housing behind a mild 186 and M21 box. Managed to shear the hemisphere bolts and spin the hemispheres taking off hard turning right. Replaced the centre and later broke spider gears being silly. Never an issue with axles though!

Trimatic and maturity put paid to any subsequent breakages. Just growly gears now.

It always leaked around the housing flange. Current advice is to tac weld the long bolt in the housing so it can be sufficiently torqued up, and use copper washer on the drain bolt?

Harv
your EK course spline axles will fitt with a course spline LSD

NO HR has fine spline

Course splines found in FE to early HZ [ 6 cly ] banjo

FINE splines found in LJ XU1 LH LX V8 HQ- HZ v8 bang go's
and late HZ 6 cly

Rob

Thanks Rob for clarifying that. Apologies Harv for my misinformation. Dunno why I had it in my head that EH onwards were fine spline............stupid brain!

Cool - thanks gentlemen.

To summarise up for the next silly bugger looking to put an LSD into an FB/EK banjo diff:
a) the LSD centre should (almost) be a bolt-in replacement for the grey motor banjo centre.
b) just like all the other grey banjo centre upgrades you will have to fit a red motor universal joint (Rare Spares UJ1004) to the FB tailshaft, and use the red motor U-bolts and nuts (Rare Spares UJK002) to mate up to the LSD.
c) FB/EKs have course spline axles (10 spline), just like FE to early HZ 6-cylinder engines. Some other banjos (LJ XU-1, LH LX and HQ- HZ V8's and late HZ 6 cylinder) were fine spline (28 spline). Both course spline and fine spline LSDs were made. To fit the standard FB/EK banjo axles, a course spline LSD centre is needed.
d) A 3/8-UNF "long" bolt is required to replace one of the original bolts. More info here on the bolt swap and retaining method: http://holdenpaedia.oldholden.com/BanjoDiffRatioChange

Now I'm just hoping the LSD in question is coarse spline

Cheers,
Harv

Harv
Yes to A to c
[ D ] TWO { 2 } long bolts are only found on 2.78 or 3.08 ratios centers
[ bigger crown wheel ]
{ i have about 8 lsd centers here , pick up only }

Rob

I'm about to do this also Harv as it looks my single wheeler is done and dusted as far as the crown wheel and pinion so might as well upgrade to an LSD 3.55 to get it running better on the highway.

I here the term "Red centre" used for the later model centres - does that just mean they are the LSD version?

FJWALLY wrote:I'm about to do this also Harv as it looks my single wheeler is done and dusted as far as the crown wheel and pinion so might as well upgrade to an LSD 3.55 to get it running better on the highway.

I here the term "Red centre" used for the later model centres - does that just mean they are the LSD version?

Not necessarily , the "grey " centres (FX-EJ) were all 3.89:1 so anything else is a "red" centre

Just wondering if anyone has the spec for the amount of torque applied at the axle before the lsd clutches will slip and transfer drive. Measured mine at 25ft lb.


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Clay,

25 ft.lb. means that your LSD centre is just about knackered. Sorry. I'll consult an HR shop manual tonight, but I think the torque required for slip is >60, probably 110 ft.lb.

Rob

Thanks Rob
Wouldn't surprise me. I have a Gregory's for FX - HR but no mention of the slippery in it.


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