Howdy estate,

The automatic transmission installed in the 122s, the BW35, was supplied to Volvo by the Borg Warner company from their Birmingham, England factory.

The BW35 has a reputation as being weak. I am not on that bandwagon. It was "weak" when bolted behind V8 engines; it was not designed to withstand that kind of torture and it certainly did have short lived service when bolted behind one. The fact that we are talking about an automatic transmission, designed nearly 60 years ago, built more than 40 years ago and is just now becoming a questionable part of your friend's car speaks volumes for the design.

Parts are still available for the BW35. It can be rebuilt. The difficulty will be finding a competent shop to rebuild it. Would I have it rebuilt if it was mine? No. I would want to upgrade to an overdrive transmission, either manual or automatic, because the price of fuel dictates all my decisions these days.

The tunnel in the automatic cars is a bit wider than the manual shift cars. I do not know how much work it would be to modify the tunnel for a T-5. Certainly less tunnel work than if you were starting with an M40 car. Any automatic to manual conversion will entail considerable effort. There is nothing common between the two. The driveshafts are different. The crossmember is different (and mounts differently to the pan). You have to have a complete donor setup with all the pieces and parts, some fabrication and welding is necessary. It is not an afternoon's romp under the shade tree. That is true whether you are installing a T-5, M41, or M46. Of the choices available, only the M40 and M41 (and maybe the M410, I don't know as I've never seen one) will bolt to the upright engine without an adapter or a rare OE bellhousing. You will have to research the swap thoroughly before buying parts. And, when buying parts, get as much from the donor car as you can. You never know what you are going to need in the middle of the project.

If your friend wants to keep the car automatic, consider the AW70 installed in the 240 in the early 80's. It is readily available in junkyards all over the USA. It has an OD top gear. It is however, NOT a direct bolt-in. You need to find an adapter to rotate the mounting holes to fit the upright engine. The crossmember will not lineup with the mounting holes in the pan, and so, the pan will need to be modified. The front drive shaft will need to be rebuilt to the proper length. The stepdown and shift linkage will need to be custom. And, I am sure there is more to it than that. It isn't easy and it isn't inexpensive. But, it can be less expensive than rebuilding the BW35 and it will give him an OD for the highway.

Go to http://www.v1800reg.org/ and navigate to the Tech Info page. Get the document "Installing a AW70/71 in a 1800". There is a lot of good information there, including a phone number for a man who was making adapters to rotate the AW70 bellhousing. I have no idea whether he is still doing so.
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Mr. Shannon DeWolfe -- I've taken to using mister because my name misleads folks on the WWW. I am a 52 year old fat man. ;-)