Usually as we increase the power output of both turbo and N/A engines, the extra power is made at higher rpm’s. Often along with these higher rpm’s the power band becomes a little narrower, either due to the lairy nature of “race” cams or by the late spooling of large turbochargers. This results in gear changes that need to be made at both higher rpm’s and in a quicker time, so as to keep the turbo or cams “on song”. A traditional syncho gearbox struggles with this increased demand, often baulking or crunching, in an attempt to change gear quickly at high rpm. In addition as power outputs go up, we start to experience gearbox failures such as stripped gears on high bhp cars, or damaged synchros due to forced “crunched” gearchanges.
The only recommended solution for these high output engines is to use a sequential dog engagement gearbox. This type of gearbox features a gearstick that moves only forward or backward, in a “pull” to change up, “push” to change down format. The gears are engaged using a ring of dogs, machined in a manner that keeps the gear engaged under load. All that is required to change gear is to pull the gear lever and lift slightly on the throttle to reduce load on the dogs. This allows clutch less upshifts and speeds up gear changes to around 0.2 of a second. In conjunction with a suitable ecu such as the AEM Infinity, rather than lifting slightly on the throttle, a strain gauge is added to the gear lever, indicating to the ecu when the driver is pulling the gearstick. At this exact moment the ecu reduces engine load by a combination of fuel cut and ignition retard, whilst the driver keeps his foot firmly to the floor. The result is a gearshift of near instant selection (typically 0.06 of a second) with the only driver requirement of pulling the gearstick. This is known as “flat shifting” as no clutch or lifting of the throttle is required during the gear change!
Ford Cosworth YB (Sierra and Escort)
For 2wd YB cosworth powered cars, we usually recommend using a Quaife 60G 6 speed sequential gearbox for power outputs up to 450bhp, and its bigger brother the Quaife 69G for power outputs of 500bhp and above! Available with several gear ratio options, ratios can be chosen suitable for road and track day use, as well as ratios suitable for circuit or rally use.
The 60G gearbox requires only minor tunnel modifications to accept the new gearlever mechanism, whereas the 69G is a bulkier unit requiring the manufacture of a new gearbox tunnel. This is a conversion we do in house, and looks like a factory installation after completion, even retaining the carpet for road going vehicles! A new multi-plate 7 ¼ clutch and steel flywheel along with hydraulic centre push are required, and a new stronger 1 piece prop shaft is used. The rear gearbox mount is custom made to fit the Ford chassis.
An optional gear position indicator (showing gear oil temp as well) can be added, to display an in car gear via a clear digital display
For 4wd cars we use the Quaife 87G 6 speed 4wd gearbox with a new bell housing allowing direct fit to the YB block. Reliable up to 800bhp, this huge gearbox requires a new gearbox tunnel fabricating, but like the 2wd cars we can perform this modification in a manner that looks factory installed, even retaining the carpet for road going cars! New uprated propshafts are required to connect to both front and rear diffs, along with a new rear gearbox mount. A multi-plate 7 ¼” clutch, steel flywheel, and hydraulic centre push conversion complete the package! Like the 2wd, an in car display is also available to show gear position and oil temperature.
Ford Escort Mk1/2
For N/A applications up to 300bhp we recommend the 7 speed Quaife 89G, or for turbo applications we recommend the 6 speed 60G, both being essentially type 9 replacements, requiring only minor tunnel modifications.
For power outputs over 500bhp we recommend the Quaife 69G as used in our 650bhp blue mk1 Escort, but this requires more extensive gearbox tunnel modifcations due to the bulkier nature of the box.
In addition, for those who prefer steering wheel paddles, we recommend the Geartronics closed loop paddle shift system, compatible with all the above sequential gearboxes. See www.geartronics.co.uk.