Transmission
One of the most notable differences between Escort and Fiesta RS Turbos is the latter’s lack of a limited-slip differential as standard. Typical of Ford cost- cutting, maybe, but not exactly critical when it comes to tuning.
That’s because you’ll probably be investing in a rebuilt gearbox and LSD before you tread too far down the modification path – if only since your existing gearbox is likely to be noisy or sloppy, and ready for a new clutch…
For mild upgrades, an AP or Helix four-paddle clutch can be used with a standard pressure plate, allowing ease of use in an everyday road car; a sixpaddle clutch is preferable for higher-powered machines. You can swap to an LSD- equipped Escort RS Turbo gearbox, but if you’re planning on more than 200bhp you’d be better advised to rebuild your existing ‘box with an uprated gear kit, Quaife ATB differential and a quickshift mechanism.
A strong, cheaper alternative is an IB5 gearbox from a late Zetec- engined Ford – ensure it’s from a car with front-fitted starter motor and has four-bolt mounting holes, and go for a 1.8- engined model to gain the most suitable ratios.
OKC also recommends the Mk5 Escort RS2000’s MTX75, which is tough enough for any CVH or Zetec thanks to its large, chunky gears, driveshafts and CV joints. Fitting it into a Fiesta will requite cutting and shutting of the inner wing, but this is a job OKC can do if you specify a complete conversion. The MTX75 doesn’t come with an LSD, so you’ll need to add a diff or at least use a Mondeo Mk1 intermediate shaft for equallength driveshafts, which helps to reduce torquesteer.
If budget is no barrier, NMS and Sitech favour the Getrag MT285 six-speed gearbox from a Focus ST170, which again includes enormous internals (capable of handling 400bhp) for a very low purchase price. The downside is you’ll need to spend thousands on a custom clutch, driveshafts, limited-slip diff and installation…