Performance diff info thread.

For non EFI mechanical discussion
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Re: Performance diff info thread.

Postby VK_3800 » Sat Jan 14, 2017 5:03 am

ejukated wrote:So just to be clear, you can mount a M78 centre in place of a M75 but ring gear and pinions from a M78 wont fit on a M75?

Absolutely yes (centre is identical), have done so myself.

immortality wrote:Just to add to this (and add a little confusion), a M78 gear set can apparently be made to fit an M75 housing (by grinding clearances) however an M75 gear set can't be used in a M78 housing.

Theoretically yes, not with hand grinding though. There's enough room for the larger crownwheel and you can swap the larger OD M78 rear pinion bearing to a smaller M75 one as they are the same ID. The trick would be machining the rear pinion bearing support in the housing around 0.15" (nearly 4mm) deeper to move it further forward for the larger crownwheel, or perhaps there is a shorter bearing that could account for this (wouldn't be my first choice though, this bearing is important). You can jam everything in there without moving the pinion but the gears won't come close to meshing correctly.

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Re: Performance diff info thread.

Postby immortality » Sat Jan 14, 2017 7:03 am

It can't be to difficult, my mate had a diff built at Steelie Gears last year and it used a M78 gear set from a VS HSV (hydratrac) diff in a standard housing. Definitely not something you would want to attempt with basic hand tools.

He's looking at another gear swap now so I might try and see if I can get some photos when it gets pulled apart again.

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Re: Performance diff info thread.

Postby gtrboyy » Wed Aug 16, 2017 9:24 pm

Any guys tried out those ebay Torque Lock LSD by Torqueline?

Supposedly true trac copies...not heard much about them tbh.

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Re: Performance diff info thread.

Postby brindo » Wed Aug 16, 2017 9:55 pm

I have a Torque Lock that's been sitting in the shed for quite a while now. Just waiting on a set of gears. And time.
Would like to have it installed before the year is out.

It looks the goods, but time will tell.

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Re: Performance diff info thread.

Postby gtrboyy » Wed Aug 16, 2017 10:48 pm

Heard a little about them where most need to grind down head of pinion gear to fit....other than that couple of guys said theirs seemed ok after the test drives but nothing since.

Diff bloke I used rather not use them unless it's just street driving.

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Re: Performance diff info thread.

Postby VK_3800 » Thu Aug 17, 2017 5:28 am

The Harrop/Eaton Truetrac requires clearance work to fit with many ratios too, was told when I bought mine that it would only be an issue with 4.11 pinion and that my 3.45 would fit fine... wrong. Its not a lot and you could take it off either the new centre or the pinion but after spending $1600 on the Truetrac vs a $50 gear set (and no real tooth contact at the end anyway) it wasn't a difficult choice.

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Location: Western Queensland

Re: Performance diff info thread.

Postby brindo » Mon Apr 09, 2018 7:22 pm

Apologies for stirring up all the dust on an old thread.

Have just installed a rebuilt M78 diff in my one tonner. Too early to say whether the Torque Lock (or my diff rebuilding skills) are any good or not. But if anyone is interested, Ratech make a solid pinion spacer kit part number 4114 - $30 delivered. And Yukon make an adjustable carrier shim kit which is pretty handy if you’re using a different hemisphere. The Yukon SK SS10 is listed as being the correct kit for an M78, but has a minimum thickness of 0.210” which is more than likely too much. The correct one that will work is the SK-SM35, which goes from 0.120” to 0.213”and was around $40 delivered. Which was cheaper than me getting the old shims surface ground.

Hope this helps.

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