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ford FWD transmission guide
Contents:
Information in this article applies to most of the front wheel drive Fords, including Fiestas, FWD Escorts, Focus models (is the plural Foci?), Ka and Puma. Information on gear ratios is at the bottom of this page and we would like to hear from you if you can fill in our blanks or if our information is inaccurate!
BC transmissions
Up to 1990, all FWD Fords were fitted with the BC transmission. These boxes are completely interchangeable, with driveshafts, input shaft and bellhousing bolt patterns in the same place regardless of the internals fitted, which is why it's so easy to fit, for example, an Escort RS Turbo gearbox in the Fiesta.
After 1990, Ford recognised the need for an improvement in the bearings on some of the BC boxes. Unfortunately, this was too late for the Fiesta Turbo which kept the older, smaller style bearings. However, two models did get uprated bearings: the 1800 Zetecs (e.g. XR2i 16v and RS1800), and strangely the 700Kg payload Fiesta Couriers. Although these uprated bearings are pretty much the same as those used in the iB5 box, note that the box was still a BC and not really an iB5.
iB5 transmissions
From 1995, Ford introduced the iB5 box which replaced the BC transmission. Fitted to all Fiestas, Kas, Pumas, and some Escorts (not RS2000, Cosworth or 130PS Zetecs) and Focus models. This box was available with a front or rear mounted starter. The rear-mounted starter is handy on Zeta/Zetec-E/Zetec-R engines as it keeps the starter away from the exhaust heat and allows more room to work on any turbocharger fitted. Unfortunately for CVH owners, the block's sump breather fouls the starter and prevents a rear-mounted starter being fitted unless you relocate this breather.
Apart from the breather difficulties on rear-mounted starters, the iB5 box is a direct replacement for the BC box. Use your existing clutch with the iB5 clutch release bearing (approx £20 from Ford).
The iB5 contained stronger input and output shaft bearings compared to the BC box, but was never fitted with an LSD (limited slip diff) in any models. A specialist gearbox builder will be able to advise on the fitting of an LSD to the iB5 box.
Gear ratios are a bit of a problem, especially on later Ford boxes where shopping trolley-power engines became the norm and buzzy boxes were fitted to help these cars get up to speed. Further down the page is a listing of some of FWD gear ratios and a link to a small Excel spreadsheet which allows you to put in your gear and final ratio, an engine speed, and your tyre size (e.g. 205/50 R16) and will calculate your road speed - handy if you want to work out if your speedo is reading wrong.
MTX75 transmissions
The MTX75 box is a development of the MT75 RWD transaxle fitted to some Sierras and Granadas. It was used in some Focus, Mondeos, Escort RS2000 and RS2000 4x4 models, and was hailed as Ford's new, heavy duty FWD transaxle. Although only ever fitted with a Quaife LSD in the Focus RS, the standard diff is partially locked and makes for good power delivery. A 6-speed variant was fitted to the Focus ST170.
Fitting this box in the Fiesta, Ka, Puma and BC-equipped Escorts requires some welding on the chassis to fit a new mount, or the fabrication of conversion brackets. One other problem lies with the driveshafts - one of the driveshafts will require modification to fit the box. For more information, your best bet is to track down a racing transmission specialist.
General info and tips
All of these boxes tend to be weakest in 1st and 2nd gears. A whining noise is often the first sign of excessive wear on the internals preceding a failure. You should use a good quality Hypoid to the specs in your handbook or, if using aftermarket internals, eg Quaife, follow their recommendations.
Topping the oil up in these gearboxes is fairly straightforward, if a little fiddly. The drain/filler plug on the front of the bellhousing, near the reverse light switch, is removed with an allen key (not a Torx bit). The oil level should be between 5mm below the level of the hole, and level with it (with the car parked on even ground). A straightened out paperclip, bit of welding rod, etc, can be bent into an L-shape to measure the oil level.
Gear ratios information
[Click here to open the ratio calculator spreadsheet] (your PC will need an Excel-compatible spreadsheet program)
[gear ratio info collated courtesy of M Brian]
| Car | 1st | 2nd | 3rd | 4th | 5th | 6th | rev | diff |
| Escort Mexico mk1 | 2.97 | 2.01 | 1.40 | 1.00 | n/a | n/a | ??? | 3.77 |
| Escort Mexico mk2 | 3.65 | 1.97 | 1.37 | 1.00 | n/a | n/a | ??? | 3.54 |
| Escort RS 1600 mk1 | 2.97 | 2.01 | 1.40 | 1.00 | n/a | n/a | ??? | 3.77 |
| Escort RS 2000 mk1 | 3.65 | 1.97 | 1.37 | 1.00 | n/a | n/a | ??? | 3.54 |
| Escort RS 2000 mk2 | 3.65 | 1.97 | 1.37 | 1.00 | n/a | n/a | ??? | 3.54 |
| Escort RS Cosworth Monte | 3.61 | 2.08 | 1.36 | 1.00 | 0.83 | n/a | ??? | 3.62 |
| Escort RS turbo S1 | 3.15 | 1.91 | 1.27 | 0.95 | 0.76 | n/a | ??? | 4.27 |
| Escort RS turbo S2* | 3.15 | 1.91 | 1.28 | 0.95 | 0.76 | n/a | ??? | 3.82 |
| Escort RS1600i mk3 | 3.15 | 1.91 | 1.27 | 0.95 | 0.83 | n/a | ??? | 3.84 |
| Escort RS1800 mk2 | 3.36 | 1.81 | 1.26 | 1.00 | n/a | n/a | ??? | 3.54 |
| Escort RS2000 mk5 | 3.23 | 2.14 | 1.48 | 1.11 | 0.85 | n/a | ??? | ??? |
| Escort XR3 4spd | 3.15 | 1.91 | 1.28 | 0.95 | n/a | n/a | 3.62 | 3.84 |
| Escort XR3 5spd | 3.15 | 1.91 | 1.28 | 0.95 | 0.76 | n/a | 3.62 | 3.84 |
| Escort XR3i 5spd | 3.15 | 1.91 | 1.28 | 0.95 | 0.76 | n/a | 3.62 | 4.27 |
| Escort 1800 130ps MTX 75** | 3.23 | 2.13 | 1.48 | 1.11 | 0.85 | n/a | 3.46 | 3.82 |
| Fiesta 1.0 5spd mk2 | 3.58 | 2.04 | 1.35 | 0.95 | 0.76 | n/a | 3.62 | 4.29 |
| Fiesta 1.0 4spd mk2 | 3.58 | 2.04 | 1.35 | 0.95 | n/a | n/a | 3.77 | 4.06 |
| Fiesta 1.1 4spd mk2 | 3.58 | 2.04 | 1.30 | 0.88 | n/a | n/a | 3.77 | 3.58 |
| Fiesta 1.1 5spd mk2 | 3.58 | 2.04 | 1.35 | 0.95 | 0.76 | n/a | 3.62 | 3.84/4.06 |
| Fiesta 1.3 5spd mk2 | 3.58 | 2.04 | 1.35 | 0.95 | 0.76 | n/a | 3.62 | 3.84 |
| Fiesta 1.6 diesel 84-89 | 3.15 | 1.91 | 1.28 | 0.95 | 0.76 | n/a | 3.62 | 3.33 |
| Fiesta XR2 mk2 | 3.58 | 2.04 | 1.35 | 0.95 | 0.76 | n/a | 3.62 | 3.84 |
| Fiesta XR2 mk2 (early?) | 3.15 | 1.91 | 1.28 | 0.95 | 0.76 | n/a | 3.62 | 3.58 |
| Fiesta 16v 1.24-1.4 zetec se | 3.59 | 2.04 | 1.32 | 0.96 | 0.76 | n/a | ??? | ??? |
| Fiesta RS Turbo* | 3.15 | 1.91 | 1.28 | 0.95 | 0.76 | n/a | ??? | 3.82 |
| Fiesta RS1800 mk3 | 2.86 | 1.91 | 1.41 | 1.10 | 0.87 | n/a | 3.46 | 3.82 |
| Fiesta 1.8 diesel 89-95 gearset B | 3.58 | 1.93 | 1.28 | 0.95 | 0.76 | n/a | 3.62 | 3.82 |
| Fiesta XR2i CVH mk3 | 3.15 | 1.91 | 1.28 | 0.95 | 0.76 | n/a | ??? | 4.069 |
| Fiesta XR2i zetec mk3 | 3.23 | 2.14 | 1.48 | 1.11 | 0.85 | n/a | 3.46 | 3.82 |
| Ka 1.3 | 3.15 | 1.93 | 1.28 | 0.95 | 0.76 | n/a | 3.62 | 3.59 |
| Focus ST170*** | 12.7 | 7.7 | 5.7 | 4.6 | 3.8 | 3.1 | 12.0 | 1 |
[* official ford brochure figures from FasterFords.com]
[** figures courtesy of Haynes]
[*** due to the twin shaft design of the box, we have included the relevant final drive ratio with the gear ratio]
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Please mail me if you spot an error, omission, or something just plain dodgy. Also take a look at the disclaimer at the bottom of the page :o)
Although every care is taken to avoid errors, neither the site nor myself can be held responsible for any errors or omissions contained on any part of this site.
If you have any queries about this article, good advice from the peeps who have done this before can be had by posting a question on the Fiesta Turbo forums. |
| ::BC box | [click to enlarge] |
| ::iB5 box | [click to enlarge] |
| ::MTX75 box | [click to enlarge] |
| ::IDing an LSD | [click to enlarge] |
| ::iB5 bearing, left | [click to enlarge] |
| ::4-paddle on right | [click to enlarge] |
| ::diffs | [click to enlarge] |
| ::diffs | [click to enlarge] |
[links]
Quaife
Race-bred transmission company with years of experience and thousands of rallying successes.
Gearboxman.co.uk
Competition transmission specialists.
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