Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Change of complete rear axle in 2014 4/4

I'm gradually giving up on finding a solution to shorten my final drive ratio. There is no other crown and pinion than the 1:3.7 for my axle. Can I change to a complete earlier rear axle in my 2014 4/4, like the one that was used in the 4/4 until around 2011 or 2012? Because then there is the crown and pinion available to change from 1: 3.7 to 1: 4.1. Or were the dimensions of the BTR axle different? It was only used together with the Ford transmission when I recall it right. EDIT, Günter Biener had a P4SS around 2011 and it had a Mazda gear box in combination with the older rear axle, je even drove a 1:4.3 ratiio.. But... was the old BTR axle exactly the same width? It sometimes seems to me that the older 4/4s were narrower at the back? Then it's not an option for mine.

Older 4/4 were on a narrower chassis.

So even the 4/4 sport that was built from 2008 on?

IIRC, all the Sigma engined 4/4's were built on the standardised, wider, chassis.

Zetec 1.8 4/4's were built on a narrower chassis - and some, if not all, featured a cut out in the main chassis rail for the exhaust to pass through - creating a weak spot where the chassis can crack.

It was earlier than that Heinz. I would need to look it up, but at the change to long door Trads, the Plus8 chassis which became the standard width was (as I recall) still Plus8 only. The 4/4 was narrow and still without a steering rack, but it's so confusing I don't remember the exact timeline. Also remember there were no Plus 4's 2001-2004.

To summarize, the chassis had not changed since the 4/4 Sports was introduced in 2008. Since around 2011, the Mazda transmission has been used, first in the 4/4 75th anniversary in 2011 and in the P4SS. As far as I know, these years still had the older BTR axle because Gönter Biener was able to change the rack and pinion in his P4SS. A little later, another BTR axle was used, which I have. There are no other crownwheel and pinion than the 1:3.7 available. Lost Simon explained some time ago that the diameter of the crownwheel was bigger and that MMC wanted not to invest in other than 1:3.7 ratios.

My question about the width of the rear has nothing to do with the choice of chassis, which has obviously not been changed since at least 2008. I am wondering whether the very late BTR axle that I have is slightly wider and therefore the rear fenders (on the same chassis) are cut wider, which I think is possible but I don't know for sure except by eye. Because my car looks more trapezoidal than the 4/4 with the old BTR axle until 2011 or so. Their look was more parallel from front to back. However, if that is the case, I cannot use the older BTR axle to change its ratio, which was used until around 2011 or 2012. I don't know for sure, which is why I started this thread.

I think your assumptions about width may be correct Heinz.

There is one other option of course and that would be to use the older (narrower) axle, it won't be much difference because the eye can detect just a few mm. Once fitted, see how it looks. Then you have options of taking a slice off the rear wings, getting bespoke wires or just wider tyres on the rear, assuming adequate clearance on the inner wing panels.

I think it was when the Roadster came in i.e. 2004 ish

Apart from the effort involved in narrowing the rear fenders a little, it would be very appealing because the car would then look less like a trapezoid. I love the look of Morgans that appear in a relatively parallel line. But there is still a question, do you think that the connection of the front wings would still be right or were they also cut a little wider at the rear on my 4/4?

And you say, somewhat more in the subordinate clause, that the older BTR axle was actually a little less wide. Is it also your assumption, as I suspect, or are you sure that the axle was narrower?

Correct again John!

When a Plus 4 returned (it was absent from appr. 2000 to 2004), management decided to put all trad models on the same heavier chassis (that of the Plus 8 whose reign had just ended.)
Curiously, Bill Beck had used the much lighter 4/4 chassis for the first Roadster, with a Lincoln V6. (what an incredible beastie!). That light chassis was great fun.

A lot of odd changes happened after Peter Morgan became less involved.

L.