Plate type LSD vs ATB LSD

Having a RWD car makes life easier ; you don't need a gearbox oil that will favour either the diff or the gearbox ; that's before I get to resetting the plates on some setups.

That said, what are you using the car for?

In a nutshell:

• If the car is for mainly track/drifting work or you fancy willywaving get a plate diff
• If the car will be a daily and you fancy more refinement in addition to something more predictable get the ATB ; an ATB is a form of a helical diff, I believe it is based on a Torsen T2 or T3 design

PhoenixCapri has used both and put a few miles on them too, and is probably one of the better people to ask.

In my experience ATB's are great for road use, and for track where you're either not gods gift to driving or don't know the track/conditions that well - I say this because they are very forgiving since they never fully lock, and will basically act like an open diff in very dynamic situations (like when you've gone beyond yourself/the car). They work via torque biasing, so you need to have something like 2.1:1 differencial across the wheels, for them to 'lock' (transfer torque to the other wheel with more grip), this makes them very good at avoiding the pushing on issue you can get with plate LSDs which are locked when maybe you might do better with it being open. But if you have a very dynamic load case, say one corner of the car suddenly unloading (like can happen on a live axle, especially on apex rumble strips..) which results in one wheel massively loosing traction, it'll just spin, since all the torque has gone to this wheel and you don't have anything to react again. Does this make it slower on exit - well yes, but the risk of it all going very wrong is much lower.

But these days I run a plate LSD with 45/45 ramp angles. Why, well because I'm now doing hill climbing and the car never sees the road. I have no doubt the plate diff makes the car faster, as it's able to make use of all the torque it has, it's easier to get it off the line and you can drive it on the throttle much more because you have a constant, even, rear axle torque split. BUT, and this is a big but, it's a hell of a lot harder to drive and you have to be confident with it otherwise it'll bite you. This is somewhat down to the 45 deg ramp angle in decel (eventually I'll go to 60deg) but just in general you have to drive it, not let it drive you...

As said, comes down to what you're using it for - mostly road with occasional track (not drifting) I'd go ATB. Mostly/all track (or drag racing, drifting etc.) find a plate LSD (bolt in a Ford 9" axle?)

I'll leave you with one final note - in my old Mk2 Escort I ran an ATB for years, and had a couple of offs, but no matter how much I pushed it (how big an idiot I was) the accidents we're relatively small and the car survived. The first time I used the car in anger with the plate LSD I wrote it off... This was due to me not driving with confidence (or the ability it now needed!) and (I'd argue) because the plate diff highlighted the major dynamic failings of the car far more than the ATB did.

Got a Glanza with manual plate LSD gearbox. Although it works extremely well, it's quiet noisy under low loads.

No experience with ATB but they're probably much better for road use.

I ran a Quaife ATB in, of all things, a Fiat 500 1.4 (not the Abarth) for a couple of years. It was the single best modification I did to the car. It evened out the torque when you accelerated, it pulled out of corners, was excellent in the wet and delightful for track. Most of the time you didn't even know it was there. The only drawback I could discern was that it cost you about 2mpg over the same car with the factory open diff. I can't recommend them highly enough. I'm contemplating one in the Elise.

Depends entirely on the car.

On most FWD setups it's not too bad, as long as you are confidence in stripping a gearbox apart. This is easier in the Peugeots XU engined cars as the BE boxes generally let you remove the diff only in situ; I think for those you still need a dial gauge and some plastigauge to be fair, but I can't remember.

For a RWD, you're probably best off leaving it to a specialist, due to it possibly changing the pinion to CROWNwheel engage. In theory that should not change however, but that's the theory...

Where is PhoenixCapri when you need him?

My 944 Turbo was the same. A friend of mine who drove it and I suspect was not used to a plate LSD found that mind did not have the same amount of bite at the front end as his S2.

I found mine fine but found that it could at times wash out wide. If you hit the corner and the throttle at quite a rate, albeit not stupidly, but still going quick enough to question some speed limits on the road, it did then come alive with its grip.

My RS Turbo had a slighty worn Viscous LSD in it. That would understeer if you were going into a corner off-throttle. Put your foot down and you could literally tighten the line with your right foot. It was unnerving at first but great once you knew how to trust it.

The best of both worlds arguably is a Wavetrac. Probably not quite as friendly as the ATD but moreso than a plate diff. They are not what you'd call a bargain however.