_R_J_K_
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then comes the cost of a tune from Mace to allow the different ratio (regardless of the diff changing the gear ratio will require a tune) that increases the cost by about $250 minimum.
As for an M80 factory LSD will that be predictable for doing skids and keeping an angle without one wheel gripping like the open centres do? A mechanic recommended the Harrop TruTrac for burnouts because of its strength and reliable whilst also maintaining the ability to be a quieter and easier alternative to welding the stocky for a daily. From what I’ve read I need a 1.5 or 2 way diff specifically for this application and the only decent one I can find for a VX V6 auto application is https://www.harrop.com.au/shop/truetrac-m78-28-spline
You don't need a tune for this. You're probably thinking of changing the PPK values for the speedo? You can do this with a Tech 2 or a box that intercepts the speedo signal, it's more of an LS thing and I'm not even sure if it's a value stored on the memcal anyway. Mace say they can't do anything for it anyway, see here - I need the speedo recalibrated as I changed the diff gear ratio from 3.08 to 3.46 and I run 235/45/17 tyres. - (maceengineering.com.au)
So what exactly is the application here? Are you going drifting or just ripping skids? The 1/1.5/2 way refers to the diffs ability to lock on acceleration and deceleration. If you're just doing burnouts a 1/1.5 way will be fine, wouldn't really recommend a 2 way for daily driving (or you might as well weld it). It should be reliable enough (It's behind an LS engine with far more displacement and torque), it could be exactly what you're after, and if it's not just wait until it wears out and rebuild it then.
IMHO there's very little point in spending that kind of money on a diff for an N/A Ecotec (until you know you need it) when a stock M80 swap is so much easier and cheaper, will be super friendly for normal driving too. Even then rebuilding the M80 you swapped in with a Truetrac centre will be far cheaper/better than doing the M78 even with the initial buy in of the diff. The Eaton M80 Truetrac centres are like $600 or something, the only thing comparable to that price in M78 world is the Torqueline/ Torque Lock diffs, then finding diff gears for them can be difficult depending on what you want.
I think you're focusing too much on the car being a VX V6 auto instead of looking at the diff itself. The Harrop M78 Truetrac really only exists to cater for the VL-VS live axle diffs that can't swap to an M80, pretty sure Harrop licensed the design of the Truetrac from Eaton to build it.
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