Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Noisy Mazda thrust bearing?

That on the left Craig is the clutch master.

Thanks chaps, that's Interesting. Two Mazda box varriants, both with pro's and con's.

Thanks Harry, it just shows you how much i know

Thanks HJF. To be sure we are talking Miata NC gearboxes? When I remember. correctly what I have seen isn't it the case that an additional hole has been drilled somewhere in the top front of the gearbox housing so that a hydraulic hose can be routed into the gearbox?

Just emerged from the garage having had a look under the bonnet to remind me how the pipe work is arranged. The hydraulic hose goes from the master to a “port” on top of the bellhousing. The port has a connection to the clutch hose from the master cylinder and also has a bleed nipple. Main issue is that it is very crowded down there and looks like it would be a struggle to get a hand and spanner in there.

Anyone on TM actually had any direct experience working on the 4/4 concentric slave and can confirm if the above is correct or not?

Is this an additional made „port“ which is originally not there in a Miata?

I believe so. Google "concentric slave" or "central slave" for images that show various arrangements.

The background why I am so interested in the 4/4 gearbox and its control is the following. At the older Salisbury rear axles of the 4/4, it was relatively easy to change the final ratio to 4.1. A different gear rim was simply exchanged. The disadvantage is that the motorway engine speed also increases significantly. On my 2014 4/4 with BTR rear axle, this simple change no longer works. I would have to buy a completely new axle. Techniques and Williams confirmed this fact four years ago. At around 6500€, this is far too expensive. A 6 speed NC gearbox would have pretty much the same effect as a 4.1 rear axle plus almost the same low cruising speed in 6th gear. In the pictures below, a, the comparison of 5 speed and 6 speed NC transmission, b and c 5 speed with 4/4 wheel circumference, d and e 6 speed. I would very much like to be able to fit a 6 speed gearbox. Despite an intensive search, I have not yet found out whether an NC 6-speed gearbox has different dimensions, especially in length, or not. In the worst case, I would have the propshaft shortened.

An interesting project Heinz. A chat with these people might be worthwhile to see if they could offer or know if a 6 speed was viable?

Ratios do matter. My 1.8 Duratec 4/4 with the MT75 was quicker off the mark than the 2.0l Duratec +4 with the Mazda box. When you dropped the clutch for a quick getaway with the 1.8 it was off in a blink. With the +4 there is a fraction of a seconds delay as the revs sag and the engine finds the torque for the longer ratio. The difference was quite noticeable negotiating busy roundabouts when I first got the +4. I couldn’t be as cocky as I was in the 4/4 pulling out into the traffic. Obviously there were other differences with the boxes but I do miss the MT75 in many ways.

Rog, thanks for this very helpful link. As seen on their page they are the guys who did all the conversions for MMC Mazda gearboxes. I am looking forward what they will write back re the 6 speed box.
BTW I think their prices are very reasonable if someone would think about a swap from a Ford transmission to a Mazda one including all part plus prop shaft for under 3.000 GBP.