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Ken had developed an innovative 5-speed gearbox which was a delight to use. It was slick, quiet and strong. It also required no modifications to the car when fitted; could be removed without disturbing the engine - and even had synchromesh on reverse. He had determined that the original MGB/C gearbox was not really up to the job in the long run, especially behind a well-tuned engine, and of course, it lacked a fifth gear.


A batch of ten prototypes was produced which elicited genuine interest from several mainstream manufactures, but sadly, he could not attract enough financial backing to make it in sufficient numbers to guarantee the continuity of supply they required.

The alternatives are:

Leyland LT77S (not the earlier versions). However, you are unlikely to find one in good condition.  The later R380 as fitted to the MGR V8 is far superior and has a matching bell housing. However, Ken didn’t like its shift quality or reliability record and much preferred:

The Borg Warner T5 (now Tremec) coupled with a matching bell housing and concentric hydraulic clutch release mechanism from John Eales Developments. A great combination, eventually fitted to Roger Cook’s vehicle (dubbed ‘the ultimate Costello’) which had become Ken’s de facto development car.

New, stronger gear sets in a choice of ratios and stronger selector forks are available from Competition Transmission Services, who can also supply Quaife products - including limited slip differentials. The foregoing two suppliers have been used by Roger Cook and are recommended. You will also need a new clutch and flywheel. Sourcing the TVR version of the T5 could also provide the former, plus the bell housing - though it's not as good as the John Eales product.  The gearbox was also used in the Sierra Cosworth (2 WD)


Slight modifications are necessary to the top of the transmission tunnel, as is a new rear gearbox mount/cross member - and you will need to have your existing speedometer recalibrated. For that task, we suggest you try: Speedy Cables. A 3.07:1 crown wheel & pinion (MGC) is the best choice of final drive ratios.


These days there is also the Mazda five-speed conversion, which is used and supplied by Frontline Developments or Moss Europe or can be had direct from Vitesse Global. The Mazda MX5 gearbox is a very nice piece of kit.  However, Ken did not consider the it man enough in the long term for engines producing vast amounts of horsepower and torque.  For their more powerful cars, Frontline uses the Tremec 5-speed box.

There is also the option of using a Toyota Supra gearbox and a conversion package marketed by a firm called Dellow Automotive from Sydney, Australia, which offers a suitable bell housing and all the other components necessary for a conversion. We can’t imagine that it is any easier to fit than a Borg Warner T5/Tremec, but we have had no reports so far.

Ken was also developing a six-speed version of his own gearbox, but after the demise of his 5-speed project, it never got past a single prototype.


More Information from the Forum:

Ben Tovey posted such an informative piece on gearbox alternatives in the Forum that it has earned its place in the Technical Details section. So here's his list of gearbox options in slightly edited form.


  1. Have the original gearbox rebuilt. (This is not entirely satisfactory, particularly with higher-powered V8s, and is therefore not Ken's preference. The overdrive in third gear is especially fragile, which is why Ken used to disable it - and is one reason why he designed his own gearbox. (That said, my MGB 4-speed - reconditioned in 1998 - is still going strong, has overdrive working on 3rd and has survived several hard-driven track days - LW).

  2. Modify the transmission tunnel and fit a five speed LT77 gearbox as found in SD1s, TR7s etc. However, apart from the relatively ready availability of these gearboxes and suitable bell housings, this option is not all that straightforward. Besides enlarging the transmission tunnel, you may need to locate a manual flywheel, change the clutch, adapt the prop shaft, modify the gearbox cross-member and fabricate new gearbox mountings. Note that the LT77 comes in a multitude of different versions, so you need to make sure that you look for the correct ratios and the serial number suffix 'D'. Even then, this box has a poor reputation.

  3. As above, but use the later Rover R380 gearbox as fitted to the MGRV8. In simple terms, the R380 is a much improved version of the LT77, though sharing same physical dimensions. A better option, but it's still not the best.

  4. The 'Ford option', which uses the Borg Warner T5 gearbox. This sturdy gearbox has found its way into all sorts of vehicles from Ford Cosworths to Volvos and TVRs. The ones we are interested in are original equipment on the V8 TVRs and 2WD Cosworths. These are to be preferred because they have the gear lever in the right place and can provide the ancillary bits we need: i.e. bell housing, clutch, flywheel etc. In common with all the options listed here, transmission tunnel and gearbox cross-member modifications will be required, as will new gearbox mounts. This link provides more details of the T5 option.

  5. Toyota gearbox from behind the Supra 7M-G engine (non-turbo 1986-1992) which has the W58 gearbox*.

  6. This is also a strong box with the right ratios and physical dimensions to fit. As with the others, you will need all the associated parts, but there is a company in Australia which does a complete conversion kit, including gearbox if you need it. Follow the link to Dellow Auto, but be warned, it isn't cheap


* The W55 version of the same gearbox has also been successfully used. Please also note that we can take no responsibility for the information which is gleaned via the links that Ben has included - LW


So there are the five main contenders. Your decision on which one you choose needs to be based on what you want the car to do and how much you intend to modify it. If you intend to keep the engine output as original, then I would probably get a quote for re-building your existing four-speeder. After all, it has lasted over 30 years. If you intend to upgrade the engine for a little more power, then the R380 becomes a possibility, with the advantage that pretty much all the parts can be bought off the shelf.


You can learn more from the MG V8 Homestead website.

If you are planning a serious engine upgrade though, then you need to look at the T5 and Toyota options, as both are capable of handling around 350BHP (or so I am led to believe) Neither of these are particularly cheap alternatives as they require lots of extra parts and time. And just in case the information above has not left you totally bored (but hungry for more) here are some additional links for help with parts and information:


 - Aluminium V8 Conversion.

 - V8 Tuner


For details on T5 ratios and dimensions:

- All Ford Mustangs

- Ford Muscle


For further information on some T5 options:

 - Ford Muscle T5 Options


Yet more T5 facts and dimensional data:

 - DD Performance


Ben Tovey isn't the only owner who's not backward in coming forward with technical information - which in this case also happens to be gearbox-related. Racer John Kemp sent us a useful spreadsheet all the way from Adelaide, Australia. It calculates your gearing for you and displays (by selecting the appropriate tab at the bottom) road speed in relation to rpm. John says it's "quite useful for working out up change points and whether or not your differential ratio is appropriate, amongst other things".

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