Banjo LSD centre

[ardiesse]

Clay,

Just looked in the HK-T-G manual. 50 ft.lb. is the specified torque to make an LSD slip.

Rob

[Errol62]

Thanks Rob


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[Harv]

Been thinking a bit more about LSD centres lately, trying to pull together bits for the meth monster project. Looks like Harrop also make a coarse (10) spline version of the Eaton TrueTrac centre. Talking to Harrop, it is a bolt-up fitment for early Holden diffs (reuse existing ring gear and pinion).

This could be a bit more flexible, as if I understand it right from Craig's earlier post the GMH LSD ring gear does not interchange with the standard GMH one i.e. if I had a GMH LSD, then to change diff ratio I would have to find another GMH LSD ring gear (rockinghorse poo).

However, if I had a TrueTrac LSD, then to change diff ratio I could use any standard banjo ring gear and pinion that fits in the FB/EK diff. The spline count doesn't matter, as the ring gear and pinion do not mate to the splines.

Techo question: Is there any difference in the ring gears/pinions over different models, or will they all bolt onto a coarse spline centre? e.g. will "fine spline" ring gears still bolt to a coarse spline carrier?

Cheers,
Harv

[FJWALLY]

Thats really interesting Harv - watching with Interest.

what was the damage on the Harrop LSD centre?

[Blacky]

what was the damage on the Harrop LSD centre?

Are you sitting down ??????









$1795.00

Heard rumours of LSD banjo centres changing hands for up to $1200 so I guess if you REALLY want one you can spend a bit more and get a brand new latest technology axle snapper that you will never wear out ....

[FJWALLY]

Hmmmm - interesting indeed - I just had my sender done but an LSD is so much better for getting power down and getting off those greasy grass areas in Melbourne winters.
I''m keen to keep it looking orriginal but if you can hide something within and orriginal banjo then why not.

[Harv]

The Harrop LSD centre would still need to be fitted to a pinion set (I can do that!) and properly shimmed out (I can't do that ). Probably a $200 job.

I've been trying to get hold of a coarse spline GMH clutch/plate LSD for a while, and have done some homework.

They typically sell for around $500 in 'au natural' condition. The clutch/plate packs no longer have spare parts, so during a rebuild some stuff has to be made from scratch. A rebuild is of the order of $1000-$1200. So buying an 'an natural' one then reconditioning it ends up being a $1700 exercise.

They also sell in rebuilt form for about $1200. Always a bit of a gamble that they have been rebuilt properly, and if they crap-out it can be hard to get an interstate diff shop to rectify under warranty.

If you are driving "normally", the LSD centres are relatively reliable. Under load, the absence of the spider gear pins lowers the chances of the diff centre grenade-ing. However, the plate/clutches tend to wear relatively quickly. For the meth monster project, I intend flogging the snot out of the driveline . My guess is that if I use a GMH LSD then an LSD rebuild would be on the cards every few years. Depending on how much I wear, the rebuild would be $500-1200. The costs stack up pretty quick.

The meth-monster will not be 100% period correct, but it will be close. Not sure when Eaton started making Truetracs, but have sent them an enquiry.

Cheers,
Harv

[FJWALLY]

Just spoke with Harrop and they dont have stock so it's a pre-order only and next batch running in mid June production and only available via order.
One question Harv - are all the EK diffs 10 spline shafts?

[Harv]

Yep, all 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).

Cheers,
Harv

[Errol62]

I think if you are spending money on your rear end an have any evil intent then fine spline is the only way. You will be twisting splines like nobody’s business with the coarse spline axles. Perhaps you could get a fine spline centre a bit cheaper and spend the savings on some billet axles. That is if you want to keep the original housing. Otherwise maybe a later Torana housing or similar that comes with fine spline axles.


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[vmx-mxr]

Hi Harv
I did some blasting for a guy in Smeaton Grange who is an old school diff specialist and he told me quite a lot about banjo LSD's
His name is Dave (must be a good bloke) David BOSNJAK Engineering & Differentials Phone: 0412 683 317
Out of curiousity what are you doing for a gearbox in the monster?
Cheers
Dave Mac

[Harv]

Plan at this stage is to run a standard grey box .

The meth monster will be a bit of a test mule. I figure on owning it for many years, and using it as my "tinkering" car. The intent is to use as many original FB/EK parts as I can, including the standard banjo housing. Document out where all the go-fast bits come from, and share it on the forum. Try to get as many of the "tricks" recorded before we lose them. Dispel a few of the myths along the way (... the best harmonic balancers are the mercury filled ones from Massey Fergusons - probably not anymore). Try to add a sprinkling of reverse engineering science as I go. There will be some weird and wonderful stuff... the grey will end up with a metric bore .

Wind the power up in the front end, and see what goes bang. Upgrade, go again.

There are some bits I know are weak - like the original open diff centres. Figure I'll replace them now. Other bits I'm less sure of. A good example would be the need to tap an additional coolant line into the Repco heads. Some say yes, others no. I'm going to lean on some gentlemen who have rebuilt 10's of these heads to help understand that one... more on that later.

Should be interesting either way

Now back to the question: do fine-spline ring gears/pinions mate up to coarse spline carriers?

Cheers,
Harv

[FJWALLY]

Sounds like an awesome plan Harv - you have many of us captivated already with the meth monsters progress.
If you come across any NOS ring and Pinion sets let me know as would be far easier to have the LSD set up before pulling the old one.

[Errol62]

Interesting question Harv. I always assumed all the banjo parts were interchangeable.


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[Harv]

Some history:

a) The Detroit Locker came out in the early 40’s. It was originally used on American military vehicles during World War II, then post-war on light and medium trucks.
b) Posi-traction (plate and clutch, similar to the early Holden LSDs) came out in the early 50’s, initially for GM half-ton trucks.
c) The Truetrac (currently made be Eaton and sold by Harrop) came out in the 80's, initially for light trucks.

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 ).