I'm building a 2.0 litre blacktop Zetec engine to fit into my Focus next year and I've been looking into fitting something other than a standard open diff into the gearbox to mate up to the new engine.

As the car is currently a 1.8 it has the IB5 gearbox for which I can fit a Ford Racing Puma viscous lsd into it - alternatively I've got an MTX-75 gearbox available to me in which I could fit a Quaife ATB diff as fitted to the Focus RS.

Unfortunately I've never driven a car with a trick diff in it so have no idea how crude/effective a viscous lsd is or whether it's worth paying a little bit extra (and finding a host of other parts to make the gearbox fit) for a Quaife jobbie.

Anyone any advice? Anyone driven with both a viscous diff and an ATB? I'm looking at running around 170-180bhp which doesn't sound like much but the car is going to be a track/sprint car so will spend a lot of time going round corners at full chat.

Cheers in advance

 

Hi, fitting an LSD will be the best thing you could do ( such an under estimated mod ), theres not much difference between the viscous and the quaife as they are not tunable as such like a plated diff. If it's serious motorsport then I would be going for a plated diff set up correctly, but either way any LSD is going to make a big difference.

 

always, always go mtx75 mate, longer gears and way way stronger than an ib5, plus you can get a diff from the states (helical) for around 430 quid delivered, and fit it yourself very easily. All the bits are availible for the focus for this box, so go for it!

 

I'm aware of the weaknesses of the IB5, I regularly try to convert people across to the MTX-75 for turbo conversions because of it.

But my gearbox has been (badly) rebuilt with stronger bearings and other components by Competition Tranmission Specialists (wankers ) so I'm happy it could cope with the power/torque I'd be looking to put through it.

IB5 is such a nicer shift too as it doesn't have double synchromesh.

It's not proper serious motorsport, more grass roots sprinting so I suspect I wont be able to get the best out of a plated LSD, certainly not my money's worth.

I'd completely forgotten about checking what's available in the States for the Focus!!!

 

in that case mate, ive only ever used atbs so i cant say if they are better/worse than viscous ones. Certainly spins both wheels rather than just one lol