Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Changing the diff ratio of my 4/4 to 4.1

Meanwhile I'm very confident that I will change this ratio. In my personal view the 3.73 ratio is way too long for such a nimble car equipped with a relatively small engine.

So my question is which garages with experiences in this regards are recommended to do the job to change the crownwheel and pinion (offered by Aeroracing) regardless if on the continent or in the UK. Or would you even let the factory do the job to be sure?



Some thoughts, the goal is not to have just a "shorter" diff for higher revs but you get much more dynamic power...plus the fifths gear is so long you have plenty of reserve when using the 4.1 ratio.

Someone here posted an online calculator months ago and using a 4.1 diff ratio would make the third gear much more usable on B-roads as well as a better cornering out of smaller curves in second gear.
For example, with 3.73 at 4000 rpm in third gear she makes 60 mph, same rev and gear shows 53 mph when using a 4.1 diff.

3.73 at 4500 rpm in fifths gear shows 110 mph (just to reach with the standard 4/4) using a 4.1 ratio results in 99 mph, which is ok and not too high reving. A 4.31 ratio would result in 93 mph at 4500 rpm, even not too short when compared with some classic car I have driven, like a Alfa Giulia 1.6 or a 1973 911 T.

...Richard Thorne, Williams, techniques, ...

So kind of "gave in" to good sense in the end (as we discussed)?

Heinz, go for the change and please share your experience!
I'm planning an adaptation within the near future.

me too! Only the costs (2000€) deterred me from.

Andre, I'm really wondering if 2000€ will be sufficient. Can you tell me who made this offer to you?
The crownwheel and pinion alone costs round about 1.100 GBP.

I think (??) Jay's did this and recall he was pleased?

Yes Richard, I remember that John somewhere wrote it was among the best of all changes regarding his former 4/4.

It is not hard to change diff.
I would think any good garage in your area could do this job .
Will check what ratio is in mine.
I know my 4/4 can keep up with a +8 up to 70 mph!
Ask the Aero owners I escorted around North Wales a few years ago.

There must be garages in your area that build rally cars ?

I have always had a 4.1 diff in my 4/4, they were fitted as standard in the 1980s. Flippin' brillant, I wouldn't have anything else.

The best rear axle specialist in my view is Billy Bellinger at JB Sports Engineering

He rebuilt my axle with a Quaife ATB diff, also highly recommended if you don't have an LSD.