Volvo OD/4 Speed Upgrade

I've been wanting to do a trans swap for the coupe for a while. The stock A trans and I have never really got along, so as I was pulling the banger for new valves and to sort the rear main oil leak I thought I could also have a look at the trans. I didn't want to go the regular route of using a V8 trans as they aren't getting any cheaper and I wanted to work to a budget (for once….. ) I also like the idea of four speeds….

This what I came up with...

The trans is a Volvo M40 from a '66 Volvo Amazon I used to own. They are just slightly longer than the stock A trans and are a very easy trans to adapt to a banger. The M40 has four well-spaced speeds and synchro, the M41 also has an OD. I would say that the OD adds another 12" - possibly a little more - to the back of the trans, enough to mean work on the centre x-member of an A chassis.


I started off with a AA truck bellhousing. The AA 'housing is two inches shallower than the regular bellhousing and allows more modern transmissions to place their clutch splines in the right place. The AA item just needed a small relief machining into the mounting face with a hand grinder - as can be seen here - to clear a lumpy bit on the Volvo 'box.


The next thing to do was centre the trans to the bellhousing, and this was the easiest part of the job. I machined up a ring to fit into the bellhousing with an internal bore that matches to size of the input shaft housing on the trans.
The ring...


The ring in place on the trans...


...and the ring locating the trans to the centre of the bellhousing.


All that was needed then was drill and tap the bellhousing to pick up the original lug holes in the Volvo trans, and then to shorten the tip of the input shaft by 10mm so that it wouldn't bottom out on the end of the crank.

With the flywheel housing bolted on I was able to mock it up on its rear engine mounts and blocks of wood to see how it would sit within the cab...

I'm very happy with the positioning as the shifter will come through the floor only about three inches further back than a stocker. I made a bracket to hold the shaft in the right place and that bracket is held in place by the same bolts that join the 'box to the bellhousing. I then made another bracket for the other end of the shaft, that goes on after the pedals are in place to prevent any flexing when depressing the pedals. It seems to work quite well, though of course, it hasn't been used in anger yet. I'll try and get a photo sorted for you.

I’ve redrilled the already-lightened flywheel to accept the Volvo clutch assembly, and adapted the Swedish release bearing to the A clutch fork so that I can use all the stock pedal assembly. It's all gone together quite well. A small bronze bush was required for the spigot bearing and a new emergency brake mount was needed, as these bolt to the side of the trans in a stocker. All pretty basic stuff, to be honest. A fairly major stumbling-block may be the conversion to open drive, but I already have a quick-change rear-end, so a kit from the Hot Rod Works made that job a real breeze.

The ratios for this trans are 3.13-1, 1.99-1, 1.36-1 & 1-1. First, second and top are almost identical to stock A, so the M40 is putting an extra ratio between second and top in comparison. They are plenty strong and get used by some of the V8 guys in kitcars over here, not to mention the rallying that Volvo themselves did with the Amazon in the '60's. There's even a version with an overdrive available, though that would need some x-member work on an A.

Here’s how the whole lot looks together just before installation….

It’s back in the coupe now…..




I'm really looking forward to giving this a test. I've just got to finish off the rear axle relocation (no torque tube....) and have a drvieshaft made up and it'll be pretty much ready to go.