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Five speed gearbox conversions

Published: 24th Sep 2013 - 0 Comments - Be the first, contribute now!

Five speed gearbox conversions
Five speed gearbox conversions
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It’s widely reckoned that converting your classic to a five-speed gearbox is one of the best modifications you can make. Or is it – and is that added cog so necessary?

Want to slip into something more comfortable as they say? Then fit a five-speed gearbox! It’s the perfect way to make your classic feel more relaxed and there’s an increasing number of conversion kits on the market enabling modern five-speed gearboxes to fit a wide variety of classics. But is it really that simple – We reveal the truth!


Anybody who has a modern as a daily driver will acknowledge the worth of that extra cog for restful economical cruising – so much so that when stepping back into a vehicle with a four-speed gearbox you’re looking for a cog that isn’t there! Quieter cruising, less wear and sometimes better intermediate gears with a modern smooth synchromesh are other benefits.


Thanks to dedicated fitting kits that are sprouting up for more classics all the time, fitting is straightforward on some vehicles and little different from replacing your standard gearbox. The excellent Ford Type 9 is the most popular ‘box to fit and prices for a used unit cost around £300 upwards due to sheer demand –  about a third the price of a recon unit from the likes of Burton Power of Essex who also provides the option of a sportier first gear ratio if required. Other transmissions usually found on more powerful classics are donated from Toyota and BMW.

The fitting kits can cost as much as the ‘box itself but are worth the money. There’s quite a lot to change; bell housing, spigot bearing, clutch (and its operating assemblies), mounting brackets, propshaft and so on and while you can cobble up something it’s so much easier with a matched and well engineered kit.

On many classics you need to modify the floor to fit the new gear lever – usually on a Type 9, the cog swapper is mounted further back. Some marque specialists offer a mod so that the existing location can be retained; certainly on the likes of a Midget or MGB you don’t really want the lever closer to you.

Of course on classics where five-speeds became a later option, such as TR7s, Ford Capris etc) fitting is as straightforward as can be although you may find that the rear axle ratio may also need altering for best effect.


Apart from the overdrive cog, enabling lees revs at the legal limit, other benefits from the swap include better intermediate ratios. This is especially true on MGAs and Bs where second is always criticised for being too low and the jump to third too great as a result.

A modern gearbox will have a slicker gearchange with unbeatable synchromesh, a point MG specialist Peter Edney points out, adding, “After fitting a five-speed to a T Type owners say to me ‘it’s great and it’s so quiet I can speak to the wife now’”. Certainly the characteristic wail of a BMC ‘box is something few will mourn the passing of.


Remember the Austin Maxi, the first British family car to boast a five-speed transmission as standard? One of the many criticisms the car had was the limited use of the extra cog due to its gutless engine – and the same might afflict your classic!

It’s all down to engine power and whether there’s enough of it to ‘pull’ that higher cog. Peter Edney concedes that you can’t drive a five-speed T-Type like a Vectra or Mondeo and the added ratio is purely for cruising once you’ve got up to speed. Jonathan Heap of JLH Minors, a Morris Minor specialist went further, “No standard Minor will cruise at 80mph with a five-speed gearbox. Indeed fitting this to any engine with less than 100bhp is a waste of time as its a very ‘lazy’ box, meaning that the engine has to be thrashed to drive it, so its hardly an economy option.”


Taking a Type 9 as an example, having a specialist fit the ‘box into an MG is going to cost around £2000 – on other classics or perhaps using another type of transmission it could be more. Other costs include the thick end of £100 to have your car’s speedometer recalibrated – although a sneaky cheapskate ‘mod’ is to beg, steal or borrow a sat nav to note the highly accurate (due to GPS) speed readings and where they correspond on the existing speedo and mark it accordingly. This may however fall foul of the latest MOT.

Two grand is a lot of money to most of us so is it worth the expense? Peter Edney says it improves the car and adds to the car’s value in the majority of cases because the next owner will, after a test drive, see it as bonus. “It adds around £1000 to the value of a T-Type,” he claims plus makes it more saleable. As for originality, that’s for you to decide but an increasing number of owner’s clubs are accepting this mod plus in many cases, it can be reverted back to standard easily enough.


Raising the rear axle ratio is one ploy but this will have a knock on effect on acceleration, perhaps to a detrimental effect. For example, in 1996 Rover fitted the tallest final drive ratio ever to a production Mini to negate its continued lack of a fifth gear. But the only reason it was able to cope was because Minis were all 1275cc now. But fit that into an 850 or 998 version and it will feel awful. Taller tyres or larger wheels (ie 13inch where 12 inch were originally fitted) is another way of effectively changing the axle ratio and easy to experiment with. Again the speedo readings will be altered.

Lastly, don’t forget good old fashioned overdrive, which does virtually the same job as a five-speed ‘box plus can give you six or even seven ratios to play with!

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