Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Differential gear ratio

My 2011 4/4 has got a 5 speed Ford gearbox.
5th gear does not make a lot of sense, maybe OK for downhill drive on an Autobahn.
I remember some have changed the Differential gear ratio.
My Morgan garage claims bad experience with this adaptation and can not offer the change.

I am still interested to get a shorter gear ratio.
Who can give advise where I might order the right cogwheels?

Does the change make sense?

Any comments appreciated!

The Aero Racing TB kit fitted to my 4/4 Sport included a 4.1 diff in place of the 3.7 fitted as standard and it made 5th gear much more useable than an overdrive. The 4.1 was definitely noisier than the standard diff. but that was the only problem. Billy Bellinger at "www.jb-engineering.co.uk" might be worth a try.

Techniques morgan in Shefford changed my 3.7 ratio to 4.11 on my 2011 4/4. Probably the best mod I have done to the car. At 70mph the car indicates an extra 300 rpm, but 5 th is useable at 40 mph and 4th useable at 30. The car is so much more “drivable” but there is always a but. When accelerating hard 1st gets to rpm limit very quickly (almost to quick)as acceleration is much improved. And as stated the diff does “ring” can be a little noisy at certain speeds. The diff noise occurs when Cruising. Apply some power it stops & letting your foot off (deceleration) it stops. I have put some sound proofing over the back part of the frame & tool tray to help. Please note I was warned that extra noise may be apparent.

I also wanted to go to a 4.1 differential. But unfortunately this is not possible with my 4/4 rear axle from 2014, so I was told by Techniques who are very experienced with differentials. A new complete rear axle would be the solution in my case which is much too expensive. But your 2009 model should be no problem to change the ratio.
Since I have about 140 hp I am satisfied with 3.7 ratio. How would it be, Hannes, to keep the diff. ratio but find a good used MX5 gearbox as a first measure? The biggest advantage is that the first two gears are longer than the Ford gearbox and the 5th gear is shorter. This makes the car more drivable, and you can use 1. and 2. very good in case you would also change the ratio.

Cheat a bit and use different diameter back wheels, easily done if you have wire wheels.

Ray, what are the options? Which wheels and from whom? Kerry

14 inch wires off an MGB? Might look a bit odd though, anyone tried it?

Well guys, that's not what Hannes means. Smaller wheels are not a realistic and aesthetic option.

Smaller wheels do not support ground clearance I am afraid.
My 4/4 sports is low already. Afraid of speedbumps

For better acceleration you need bigger wheels.....I think

Stefan