Banjo LSD centre

[Errol62]

I’ve manage to break spider gears by dumping the clutch just a few times behind a mild red. Old mate was forever snapping coarse spline axles in his 186 HT.


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[Harv]

From the discussion above, I learned that to swap in a later banjo centre to a grey motor diff housing you had to use a "red motor" rear universal. I didn't really understand why until doing it myself.

The image to the right below shows a grey motor rear uni, whilst the image to the left is for a red motor. The green-circled bits fit into the tailshaft, and are pretty much identical so the red motor uni slips readily into the FB/EK tailshaft.

red versus grey rear universal.png (606.59 KiB) Viewed 825 times

The trick is in the part of the universal that connects to the diff centre. The grey motor part is circled above in red, and is a bearing cap that bolts to the diff centre. The bearing cap has a lug that locates on the centre, and helps to take some of the torque load (along with the four mounting bolts). The red motor diff centres do not have the machined slot for the lug. Instead, they are machined round to take round red motor universal caps, as shown circled in blue above. The round slots are shown in purple in the diagram below, which shows how the red motor universals are mounted using u-bolts instead of the grey motor bolt on caps.

red motor rear universal joint.png (1.91 MiB) Viewed 825 times

From some rough measuring, the u-bolts are 3/32" wider than the old grey motor universal bolts.

So if you try to use the grey uni, the lug will not take up load (so bolts may snap) and the bolts may not line up well (so the grey uni bearing caps would sit cockeyed).

Cheers,
Harv

[FJWALLY]

Nice work Doctor Harv,

Following up from my Harrop tru trac install - they offered at the time a few options on spline - I stayed 10 spline to keep the axles etc the same and apart from replacing bearings and seals as a standard process they kept the same crown and pinion and I can't remember what they did to the uni but think the changed the shaft end over - will take a pic next time it's on the hoist.

[Errol62]

Just did the swap myself. Purchased new hardie spicer u bolts. Couldn't get the locking plates but the u bolts came with spring washers.

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[Harv]

Some info that may be useful when the next bloke has to butcher the filler plug to get it out. The filler plug is 3/4-16UNF, the same as -8AN. Replacement genuine filler plugs are pricey... -8AN plugs much less so.

Cheers,
Harv

[Errol62]

Handy to know thanks Harv. You could always weld a half washer on, race care style.

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[Errol62]

Early holden parts, holdenman restomotive do the locking plates for about $9.

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[Errol62]

I enjoyed reading-reading this, thanks Harv. I will have to check my facts, as I read somewhere that the factory banjo fine spline diffs were 23 spline. On an FB axle you might be able to use UC 10 bolt axles, though they would be a bit longer.


FB ute fixer upper, EK van on rotisserie