Banjo LSD centre

[Errol62]

What brand of glue you sniffing Harv? I’ll have to give it’s try.


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[59wagon]

When I take her to the track she really shines (Giddyup, giddyup, one-three-eight)
She always turns in the fastest time (Giddyup, giddyup, one-three-eight)
My three-speed, dual-strom, posi-traction one-three-eight (one-three-eight,one-three-eight)
Giddyup, giddyup, giddyup, one-three-eight
Giddyup, one-three-eight
Giddyup, one-three-eight
Giddyup, one-three-eight
Nothing can catch her, nothing can touch my one-three-eight, one-three-eight

Cheers,
Harv (with apologies to the Beach Boys ).

Hahaha. That's better than the original.

Cheers,

John

[Harv]

I managed to pick up a coarse-spline banjo LSD centre a few months back. The gentleman was kind enough to store it for me for a few months until I was local enough to pick it up.

The centre has the following markings on the ring gear:
• D stamped into the surface. No idea what this is.
• 87880 engraved (not stamped) into the surface. No idea what this is.
• +3 (maybe +31) engraved into the surface. This could be 0.003", as the differential side gear thrust washer shim. They were shimmed 0.005 and 0.010 from the factory (VS10374 and VS10375).
• Holden – 7421478 – 3.55 ratio AV stamped into the surface. I'm guessing 7421478 was a casting number rather than a part number. Anyone know for certain what Holdens were fitted with coarse-spline 3.55 LSDs? Or what the AV stood for?

The LSD is relatively clean and operable, though needs a decent clean-up. Anyone tried rebuilding a banjo LSD at home? Any harder than rebuilding a grey crashbox? The torque settings etc are in the HR Holden Workshop manual. I know parts (other than bearings) are unobtainable, but wondering whether this would be simple enough for me to attempt without taking it to a diff specialist.

Interestingly, the HR (and HK) Workshop manuals show a home-made tool (with dimensions) that is used to measure the breakout torque at the wheels for early Holden LSDs. It rang bells when I saw the drawing, and as luck would have it I had one. It came as part of a bunch of dealer tools that I bought years ago, and I could never work out what it was.

Now I just need to stop Grace working out what the LSD is, and claiming it for her ute .

Cheers,
Harv

[Errol62]

Not certain but I believe 3.55 LSD optional on HR, maybe HD, manual.

I did try changing over LSD centre after I stupidly broke a spider gear in my 3.08 LSD behind 192 Yella Terra 1/4 race cammed EK215. Didn’t do a very good job as it growled from the get go.

At the time I was on zero budget. I wouldn’t attempt it now.


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[Craig Allardyce]

Harv I haven't overhauled a banjo LSD but have done few standard centres without the dummy pinion and arbour. Just make sure you have a few spare pinion bearing shims and a solid spacer. Later diffs had a collapsible bearing spacer that is a one off use item so to set the pinion depth you need the solid one, then on the final fit up use the collapsible. I used the standard pinion flange as a pulley for the spring scale. It happens to be exacltly half the size of the GM spec pulley. Just alter the reading accordingly by half.
I also measure the crown wheel adjuster depths and centre punch them so the go back in the exact position. I rely heavily on the new bearings putting everything back to the original position i.e. crown wheel to pinion relations ship. You may need to tweak the crown wheel in to take up some backlash due to wear on the gears. If you have a fairly good gear set it should be all good. BTW I only use Timken bearings as per original for sake of maintaining dimensions.
I cant see the LSD clutch arrangement being difficult at all just being springs and plates. So I'd image just inspecting for wear and checking spring conditions etc and as you have worked out doing a break free tension check. I reckon the LSD part would be easier than setting the bearing preloads and gear set tooth contact.

[Harv]

Agree - the guts of the LSD are a lot simpler to reassemble than a standard centre.

I had the opportunity to buy a full set of banjo arbour/spacer/tooling some time back that had come out of a TAFE. The seller wanted a small fortune at the time ($3000), so I suspect he still has it. Wish I still had his details.

Cheers,
Harv

[Errol62]

Had a browse through my newly acquired master parts catalogue and parts are listed for HR limited slip diff.The crown and pinion sets are interchangeable so theoretically they would have been available in 3.36, 3.55 and 3.89 ratios, being the ratios listed for HR.

Note that the EH to HR 1:3.89 gear set is a different part number to the 48 - FJ - FE to EJ gear sets. Dr Terry pointed out on the FE FC forum I think, that the EH HR set was a ten tooth pinion and 39 tooth crown wheel, so actually a 3.90 ratio. Whereas the earlier units were all nine pinion and 35 crownwheel teeth.

I wonder if anyone has fitted a limited slip, or for that matter open EH HZ case to an early 3.89 carrier, or vice versa, fitted the earlier gear set to EH on carrier and case??


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[Jenko]

Hi all

I have read through and enjoyed this thread. I was thinking of a centre swap to a LSD as well, but I think it may be too costly. I am on a more time than money project. My car is a bitsa. Half a Holden and Half an MGA. The rear drive is a Holden and there was a 179 in there driving it. I am taking the straight 6 out and havent decided what to replace it with yet. I want to leave the rear generally speaking, but still open to a LSD.

I attach a picture after I managed to get it out. First time in disassembling a rear end. Very happy to be having fun like this.

Can you guys tell me what I have here and what I would need to do to get a LSD... ?

Thanks

Rich

[ardiesse]

Rich,

That's not a limited slip diff. The only common parts between a standard diff and a LSD are the carrier, side caps, side bearings, crownwheel and pinion, pinion bearings and spacers. Basically everything between the side bearings, with the exception of the crownwheel, is specific to a limited slip diff.

If you want to turn your diff into a LSD, you need to buy a donor LSD to raid for parts. Which means - you're best off buying a limited slip diff complete.

Rob

[Jenko]

Rob,

Thanks for the reply. Yes I know mine (pictured) is not a LSD. The idea would be to replace this whole centre including the carrier with a swap in LSD unit - if that is possible.

So I think I need to know whether mine is a fine thread or course thread for a start. I'm sure that there are numbers of the ratio and also possible to count the teeth on the two side gears?? I will try to read them all tomorrow when I get time to have another look and then see what I come up with.

I was hoping for a second opinion from people who have done this before. Also, where to buy such a thing and how much roughly I should think to pay. I live in Sydney.

Thanks

Rich

[Harv]

Thanks for the reply. Yes I know mine (pictured) is not a LSD. The idea would be to replace this whole centre including the carrier with a swap in LSD unit - if that is possible.

So I think I need to know whether mine is a fine thread or course thread for a start. I'm sure that there are numbers of the ratio and also possible to count the teeth on the two side gears?? I will try to read them all tomorrow when I get time to have another look and then see what I come up with.

I was hoping for a second opinion from people who have done this before. Also, where to buy such a thing and how much roughly I should think to pay. I live in Sydney.

G'day Rich,

The easiest way to check whether you have a coarse spline or fine spline diff is to take a look at the axles (or where they slot into the centre). Coarse splines have 10 "teeth" on the axle, fine splines have 28.

To upgrade the banjo diff to an LSD, you bolt in the LSD centre. You may need to change the fittings on the nose of the centre to suit your tailshaft - these changed with various Holdens, and may be different in your MGA/Holden. You can purchase an entire LSD diff, though the easiest way is to just purchase the LSD centre, and use your own diff housing. LSD centres are often on eBay, and cost around $500 for something that is in an unknown state, and around $1000 for something that has been "overhauled". You take a bit of a risk with "overhauled" ones... I'd suggest going the $500 route and getting it overhauled yourself. Craft Differentials (out near Parramatta) can overhaul the centre and fit new bearings and seals to a banjo for around $660. I'm planning on taking the diff for my own grey-motored project to them this weekend.

As an aside, Craft were able to answer my techo question from a while back: there is a difference in the ring gears/pinions over different models, so you cannot bolt a fine spline ring gear to a coarse spline carrier. This limits the ratios available for coarse spline diffs.

Cheers,
Harv

[Jenko]

G'day Harv mate,

That's good stuff. Turns out mine is a course spline - 10 teeth. Ratio is 3.36:1. My tail fitting is a Holden too and I will need to match that up when I decide on a motor, as I will need a new driveshaft due to length. My go to idea is replacing the Red 179 with something like a V6 (VX ish) as the shorter length will suit the engine bay better. That is all "future".

Thanks for the shout out of where to take things. I agree completely on getting something not "rebuilt'. The only way to be sure is get it done yourself.

Cheers

Rich

[Harv]

I ended up getting the LSD rebuilt by Craft Differentials in Granville. They did quite a neat job. Turns out the LSD I bought was pretty much flogged out, so perhaps lucky for me that I didn't try a home rebuild. Learned an important lesson: when dropping off a diff, try to remember to include the half-moon retaining plates. If you forget, you will spend hours pulling the shed apart looking for them... before finally remembering that you left them under the house with the brake drums .

I learnt one quite useful bit of information (other than that you can still buy new spider gears for them). The crown wheel and pinions from the fine-splined LSDs can be used in the coarse-splined LSDs. There are slight differences, but not insurmountable. This gives a very wide range of diff ratios that can be made whilst still retaining the early Holden coarse-splined axles.

Cheers,
Harv

[Errol62]

Good to know about the gear sets and spider gear availability.

I wonder about the feasibility of going to fine spline axles for the extra strength. Then I think if the axle doesn’t fail it’ll be the spiders. That is the point where everyone goes to borg Warner I guess. But now you can get truetrac centre for banjos maybe worth considering?


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[Harv]

One of the things I am looking forward to with the Meth Monster project is flogging the hell out of a grey motor/crash box/banjo setup, and seeing what breaks. Some stuff is obvious, but there are a hell of a lot of "myths" out there. A case in point are the rumours that a points setup is unreliable, and need frequent servicing. I've had the same set of points in the FB for a loooong time, and they still look (and work) well.

The lumpy humpy and hambster crowd do a lot of hard miles, and whilst some gear is broken it is not overly frequent. I'm curious to see how long I can get the diff to last. The diff mob reckon that even at 200hp that it should hold up well provided I don't get stupid with it.

The truetrac centres are cool - would like to drive an early Holden with one fitted and see how they respond.

Cheers,
Harv