Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) superflous 5th gear

Today was my first day driving my 44 on the german autobahn. I was not able to figure out why the gear box has a fifth gear. Maximum speed in 5th gear was 150 kmh at 4000 rpm. Was not able to go faster than this. So i changed into 4th gear and all went fine.
is this normal or is something wrong with my gear box? 4200 km on the odometer by now.

Mine is 4 years older than yours with the MT75 Ford gearbox rather than the MX5 box on yours. I don't understand why that would be.

In 5th gear your engine will turn over at less revs so less noise and lower fuel consumption.

Due to the the way the power band is set up you may find that the maximium speed is the same in both gears.

Use the first four gears to make progress and use 5th as a cruising one. An overdrive if you will.

Note the rpm at 90 km/h. The rpm max is at roughly 6600. Deduce the theorical speed max and you will understand that it is an overdrive.

On my 2005 Plus 4: 270 km/h !!!

On my Plus 8 Auto 5th and 6th serve only to reduce rpm at a steady speed to save fuel. 4th is the classic "top gear", 1:1.

The others are both "overdrives", with 6th reducing revs to 1500 at 70mph. So 32 mpg is easily achieved, despite the 4.8L motor. Using "Sport" mode causes the computers to ignore 6th and makes it much more fun, mpg drops but not masivly, to 25 to 25.

Today's motor industry is obsessed with reducing consumption, hence my BMW 320 has 8 speeds, the computers conspire to keep the motor within a very narrow rev band, to optimise consumption at the cost of making it utterly tedious. The car can be set in "Sport Plus" mode when 7th and 8th are ignored and shift patterns altered so it is almost fun.

Fuel consumption suffers, dropping from 38 to worse than my Plus 8. The engine, a GDI Turbo, sounds horrible when pushed.

Beneviro,

give her some 10K more km for a good running in. Try 98 or even 102 octane which betters the mid torque on the ti-vct significantly - and therefore makes the use of the 5th gear more usable. At least you can keep in 5ths longer on slight climbing in comparison to use 95 octane.
Yes, some engines benefit a lot of higher octane like this one, others don't care.

In addition, the cheapest solution to get in some colder air is to put an air hose on the airbox. I'm on vacation, but next week I could take a pic or two. It's very easy to install. For me installing the hose was only a test, if something more durable will work, but I kept it and it works till now, currently in Italy on vacation, almost 40 C hot...

Otherwise, the other posts are right, the 5ths is a cruising gear. My little "tuning" was not done, to make her a racing car, but it is a nice feeling to cruise with less consumption and less flooring the pedal in 5th.

When I fitted a 5speed to my x/flow I found lower tyres suited the set up very well.

Jon the Chief

Thank you very much for the explanation. I will recognize the 5th gear as a kind of overdrive and will use it to reduce fuel consumption when cruising at a speed that i have reached prior within 4th gear ;-)

That all sums it up well, I rarely use 5th unless on motorway and it is very economical