Whoops.

I took the Mini to Beach Hop, a week of 1960’s Americana on the Coromandel. The Coromandel is pretty much all winding, hilly roads: perfect for a Mini (but not so great for the big yank tanks). I suspect I might have been a bit too enthusiastic with the cornering speeds, letting the inside wheel lift and spin a bit too often. The gearbox developed an unusual clunk when starting off, and the wheels had a bit more rotational play than seemed right, especially since I’d just rebuilt the gearbox and shimmed all the slop out.
Nothing for it but to pull the gearbox again and see what’s going on.

Oh my, look at all those pretty sparkles in bronze and hardened steel blue.

They’re what’s left of the diff’s planetary gear bushes:


Turns out a standard diff really isn’t up to an uprated engine and enthusiastic use. I guess I could install a cross-pin diff, but since this is the second time it’s been apart in as many months I went for the nuclear option:

Quaife Automatic Torque Biasing diff. It’s a geared diff (like a Torsen) so it never fully locks up, but it does direct the torque to the wheel with the most grip (up until one wheel lifts off, then it acts more like an open diff).
It’s also indestructible. Allegedly. We’ll see.
I slapped it in there, put everything back together, and went for a test drive: the damned thing tried to torque bias me into the next lane.

Once the panic had subsided (I spent *how much* just to ruin the Mini?) I did a bit more research and have made substantial improvements.

The main problem in my case was driveshaft-angle-induced torque steer. When a driveshaft acts through the CV joint at an angle most of the torque tries to rotate the wheel in the drive direction, but some of the torque tries to turn the steering knuckle. Our Mini was at a sensible, relatively tall ride height, which gave the driveshafts unequal angles due to the Mini’s unequal driveshaft lengths. This meant the left wheel got more steering torque than the right wheel, leading to a pull to the right when accelerating (and to the left when decelerating).

The cure was to spend a few days grovelling around under the Mini with a digital angle gauge, lowering the suspension until the driveshafts are perfectly perpendicular to the wheels. Driveshaft not acting on an angle = no torque trying to steer the wheels. The adjustments were surprisingly sensitive, with very small changes to ride height disturbing the driveshaft angles quite a lot. And every time I adjusted something I had to go for a drive to let the suspension settle… my neighbours probably think I’m a hoon (I mean, I *am*, but they don’t need to know that). In the end it only needed to drop about 12mm, so it’s ended up pretty much standard height.

That cured 95% of the scary torque steer. Making sure both sides had exactly the same camber and caster cured most of the rest, though the steering is still a bit lively when the diff’s hunting for traction while cornering or on a slippery surface (expected), and there’s a disturbing twitch when lifting off at 100kph.

Traction through corners is *ridiculous* now, as long as you’re ready to show the steering wheel who’s boss. It’s not arduous, you don’t need muscles like the hulk, but it’s a big change from the Mini’s previously light, precise, communicative steering.

I’m still not sure if I like it or not. I might get used to it. Or not; watch this space for a discount priced, lightly used, Quaife LSD.

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