Out with the M56 5 speed and in with the M66 6 speed with LSD

The M66 all cleaned up and waiting to install LSD

That’s gotta be the longest title for a post on this blog yet, and in like fashion this particular modification will rate as one of the more significant aspects of Ovlov’s  evolution.

When considering this change I have to admit wavering on the issue for some time. The existing M56H is a great gearbox. It’s completed 260,000klms and 130,000 of those whilst in my care. It remains in excellent working condition and will continue to do so for some time more yet. The M66 won’t give her a better top speed and may not even be as robust as the M56 and so you might wonder why proceed in this direction.

One reason being my concern around availability of another M56 should this unit eventually fail and particularly as she’s been spending more time as a track vehicle. As such when the opportunity arose to pickup an M66 from a V50 t5 for a bargain price, I could hardly refuse. There are increasing numbers of the M66 gearboxes out there and decreasing numbers of M56’s. It makes sense to make the change now and find out exactly what’s involved and have access to further M66 stock if required.

I know that M56 and M59 gearboxes can still be found, but the reality is that they come with the car. i.e you gotta buy an old manual 850 or s/v 70. This is increasingly problematic as it takes considerable resources to find, buy, store and strip parts from these old girls.

The fact that Ford also utilized the M66 box in it’s Ford Focus XR5’s, also known as Focus ST225 outside of Aus, adds to the availability of boxes and associated parts. For example, the Mfactory LSD intended for install in this upgrade is not found anywhere listed for Volvo vehicles, only Ford Focus.

The LSD is an aspect of the upgrade which I’ve been very keen to address and the additional traction will be warmly welcomed. I had learned to manage the limited traction of the open diff in track day events but this has without a doubt, limited the capability of this car. How the newly installed LSD will ultimately effect performance and drive traction will be interesting to experience and I am certainly excited about getting to that point. In terms of road use, it will I hope be a nice change not being caught unaware with sudden changes in direction under hard acceleration. It can be a little scary at times.

And so to kick this all off I’m going to post around this modification in a few stages. This post is also a pre cursor to the actual change and for anyone out there whose already undertaken this swap I’m listening with open ears. I’ve been researching this for some time, at this point the only unknown relates to the fabrication of a new engine mount on the rear passengers side (au). Other than this I believe we are good-to-go.

Given that this is the 2 wheel drive M66 swap, and we are swapping into a vehicle which has an existing manual gearbox, and there is no dual mass clutch plate to be concerned with, and the existing M56H has no inbuilt speed sensor, the process is somewhat simplified.

What is required?

• A new clutch plate to match the change in the spline on the M66 gearbox. On good advice I’m told that the Sachs SD693 clutch plate can be utilized in conjunction with the existing R series pressure plate.
• The existing hydraulic clutch line will need to be replaced/modified, as the M66 utilizes a different style of slave cylinder.
• The gearshift lever assembly will require some fiddling as there are differences in the way existing cable connects to the gearbox, but again, others have been there before me and completed some modification  to existing brackets without too much difficulty.
• The fitting of the Mfactory limited slip diff will require that the diff bearings be replaced and some new gearbox drive shaft seals installed.
• The M66 will require an OEM thrust bearing but this is simply because the old is worn out. Not a modification as such.
• The rear engine mount on the Passenger side (AU) of the engine will require fabrication of a new bracket and mount.

While all of this is going on, long overdue replacement of the sub-frame bushes will take place, a job I’ve been wanting to address for ages 🙂

I thought I’d keep a running tally of items on this part of the project, including links and prices which may prove helpful to anyone wishing to undertake this same modification.

• M66 Gearbox – 2006 V50 T5 FWD – Sydney Motor Recyclers $80 (yep, it was a bargain buy)
• MFactory Helical LSD – Suitable for Ford Focus ST225 M66 6 Speed –  Of note, Mfactory only list this unit for the Ford Focus XR5 (AU) or St225 (overseas) but I did confirm it’s compatibility. Purchased from Diff Lab $1000 au
• Sachs SD693 Clutch plate – Purchase from Rock Auto $70 au
• Sachs SB60223 Release Bearing and Cylinder Assembly – Purchase from Rock Auto $120 au
• SKF Differential Bearing x 2 – SKF 32008 xt9/q or National NS32008 – Source from Rock Auto $25 each. (I noted that some M66 gearboxes utilize a larger diff bearing 32010 x. I suspect this larger bearing must have been for later model m66 gearboxes. Best to check what’s in your gearbox before ordering)
• Gearbox Input shaft seal -Part# 8675580 – FCP Euro – $15
• Drive shaft axle seals – Part# 6843481 – FCP Euro – $7 each
• Modification of existing clutch line – again, from a local supplier with cost unknown TBA

At this point in time, aside from the process of purchasing the required items above, I’ve opened up the M66 box to inspect condition which looks great. The fitting of the LSD looks to be quite straightforward with the only significant consideration being the need to maintain appropriate spacing tolerances when fitting new spline bearings, I think!

Footnote – Some may be wondering why the MFactory helical LSD when the common options are Quaife, Wavetrac, or Gripper.

• I like to be different. 🙂
• I found a local distributor.
• They seem to have some genuine street cred in the performance sector.
• The price was about 20% less than nearest rival.
• They claim superior product as a result of manufacturing techniques.
• I could find no online threads to suggest they are crap, quite the opposite.

I guess I’ll get to find out in a several weeks but in the interim here is a little more info which may be of interest.