The Diff

So here’s the tangle. I’ve a Triumph GT6 chassis, strong as a ship’s ladder, and into it I’m trying to graft Mazda’s tidy little drivetrain. But Mazda, in their wisdom, never imagined their gearbox and diff would be divorced. They tied the pair together with that great aluminium spine, the Power Plant Frame, as I've discovered tat it's called. Trouble is, the GT6 chassis rails were in the way, so off came the PPF from the Mazda gearbox. It was only there to carry Mazda’s aluminium spine anyway, so no great loss — except it reminds me that what I’m doing is tearing up the rulebook.

And what did I find with the replacement chassis? What looks suspiciously like a Torsen 2 diff (which is what I need), but butchered to fit and never intended for serious work - certainly not for a turbo engine. The whole Mazda rear-end fabrication had been built around that bodged unit, powered by a Spitfire engine, not the full-width Torsen 2 that I actually need if I’m to handle proper power without the back end tying itself in knots.

Above you can see the two diffs - the lower is the old Torsen 2 (it may not even be an LSD, although it looks identical) with the butchered arms, and the upper is the full-width Torsen 2. 35cm separated support in the former and 60cm in the latter.

So there’s the rub. I either get the welder in (structural stuff is important and beyond my pay grade) and build mounts stout enough to tame the twisting forces, or I try to lash it together with old GT6 ironwork and rubber bobbins pinched off a Mini. 

One path is proper engineering, the other is an invitation to vibration, propshaft misery and gearbox mounts that won’t last a fortnight. All because Mazda never imagined some lunatic would be shoving their running gear into a 50-year-old Triumph — let alone with a turbo strapped on.

Sense dictates some fabrication on the replacement chassis' rear end to take the full-width arms. The list of work just gets longer and longer, but it will be worth the effort and I'm learning so much.