gearbox is the ford ib5 which is in itself an evolution of the 'bc' box which started life as a 4 speed in the first fiesta.....ib5's were introduced with the fiesta mk4, puma etc and used in low power focus', all ib5's (and bc)have a bolt on 5th gear (an after-thought), bc parts should fit but its all or nothing....the differences are subtle but many so basically you could use gears from an older car etc or vice versa. the ib5 has a focus bearing on the end of the main shaft and a thicker final drive as well as being 'top mounted' rather than 'under slung' with a cradle. to use the ib5 in an older car requires about 5 longer bolts & the mounts from the older car. to use an older bc box in an frp etc you'd have to start welding things or use an ib5 casing etc... ib5 is also hydraulic clutch, bc isnt
ib5 is only good to about 150bhp and with the frp being over this and more importantly 162nm the shafts had to be strengthened;
1st gear is shot peened to reduce stress fractures
(1.7 pumas have a torque limiter in 1st gear as even 125ps is a struggle for the ib5 over a lifetime)
frp final drive is a very respectable 4.25:1 (same as the 1.4.....!!!)
(you can beat that by using a final drive from an orion 1.4 (iirc) at 4.29:1 & if you find one let me know so i can swear at you!)
80 cars were bought as 'track' frp's (lsd fitted; viscous) has a sticker on the gearbox end cover (jack up car; rotate a wheel (out of gear) if other wheel goes SAME direction youv got an lsd)
escort rs turbo lsd's should be a direct swap but be careful; most will be completely toast by now. (car will have heavy steering; REPLACE lsd or risk snapping very rare frp drive shafts!)
update; rst S2 lsd is a swap, S1 requires mods as casing is bigger apparently
ford lsd's (wellman??) arent brilliant. their viscious which is ok but can require maintenance (and remember its not just £50 labour & £30 parts for a diff.....its £100 labour just to remove & refit a gearbox....£250 to strip the gearbox & rebuild and then the cost of anything to the diff....)(these are all old prices too; last time i paid anyone to do a gearbox for me was years ago!!)
other than the frp lsd's were fitted years ago to the rst (NOT THE FRST) and there gonna be knackered by now (unless your very lucky but ford fans arent the most honest of enthusiasts)
viscious diffs are ok, £300 new from ford but your better off with a quaife in the frp (£500). the frp is a road going racer so put the road going racer of a diff in it. quaife can be a bit twitchy for a month or too but awesome after this.
in a corner....
an open diff (standard) will force you wide
a viscious lsd will control this but still push you wide
a quaife torque biasing diff will sense the outside wheel has more grip and throw power to that wheel; it forces the car into the corner!
a proper plated diff (ie setup for individual tracks) is the best but harsh on the road
iv tried all bar the plated & will admit i only bought frp / puma because it had an ib5 and i knew the quaife diff from my bc fiesta mk3 would fit! otherwise id have never bought a ford again! but there was no-way i was selling my quaife diff; worth every penny. some can seem to take a while to bed in and be harsh, mine was but one day that was it & drives like your going through butter.
more power vicar? your going to need to change the gearbox!
people are running nos in frp's and with anything if your gentle you may be lucky but ford motorsport know the gearbox is at its limit (shot peening aint cheap!) and id be inclined to go with their thinking. for a reliable power build your going to want to;
1; uprate the box. talk to cts (competition transmission services)
2; change bits in the box (see above / quaife etc for gear kits)
3; use a different box. anything with a transverse (powerful) engine in the ford stable is using an mtx box (altho some newer cars ie 6 speed have an even newer box). the problem is that the mtx box is a good inch or 2 longer.....now go look at the engine bay.....not gonna fit!
To fit a 5 speed in an old 4 speed fiesta people do sell kits to cut the chassis member and then add the strength back with braces.....so anythings possible but id leave it upto an engineer to design such a kit (unless you want to kill your passenger if you have a good frontal crash cos the chassis member will more than likely collapse forcing the gearbox into there legs.)
leaks? 3 main areas all in 'middle' (ish) of car
1&2; diff/driveshaft seals; can get old. couple of quid & an hour plus some oil or £80ish at a garage
3; gear selector linkage seal; £5 & 30mins or......?
top up with 75w90 transmission oil using 8mm allen key plug on front of box. (i use an old hose trimmed to push just into the hole & a funnel)
fill unto 1cm from the hole (use bent end of allen key as dipstick)
you should never need to top it up; when the clutch is changed the box loses most of its oil so they top it up.....(unless you do it yourself; see my other guides)
next to fill plug is a sensor....reverse light switch
back of box (next to exhaust) and ontop of the diff is the tacho sensor for speed and mileage (not rev counter)
2 lumpy bolts on front / angled down are gear index's
CLUTCH
frp is same as std (125ps!!!!!!) and is basically crap! the focus 1.8 is the biggest engine iv found that uses the ib5 and as such has a bigger clutch. 220mm vs the frp's 210mm. most importantly its inner diameter is a touch smaller too; making it a mega surface are. its a direct swap, cheap as chips, even a little easier to press down and a hell of a lot nicer to drive than a helix etc whilst bearing pretty much as powerful. iv had mine in for nearly half a year already & its solid. def a keeper.
think thats about it.....