BW 12 Transmission versus DG250

UK Car - The auto transmissions are heavily discussed here, and I saw a recent comment that the BW12 was a direct swap for the DG250. Although the DG250 in our car was rebuilt (at significant cost) it is still a pretty agricultural drive, and I cannot find a firm / specialist in my area to ‘adjust the bands’ - without such adjustment the friction material will burn away and we’ll again be left with a dead car.

The question then, are there any smoother more reliable transmissions such as the BW12 that are an ‘easy swap’? As stated, we’re in the UK and the ‘Johns Car’ kit is not an option, nor is the Whitehouse Autos upgrade costing GBP7,000!

Also, any suggestions for a firm that can adjust the DG250? We’re in Wirral / North West England.

Have you considered the Borg Warner Model 65 or similiar Model 66 as used in the XJ6 cars to the end of production in 1987? It’s a more modern gearbox than the DB250 or Model 12.

Well I don’t know the DG but on the BW 8, 12, 65, 66 and probably 35 the bands are relatively easy to adjust. Find a good shop aka down to earth honest guy and bring the instructions, those must be in the manuals.

I understand the DG has direct drive in 3rd which must be nice for economy and it is original to the car. The BW8 and 12 are very good and strong transmissions, the 65 is garbage, the 66 slightly improved. The 35 is too weak for larger engines. The 65/66 have a higher stall converter which I hated (a real slushbox), the BW 8 I enjoy now is much nicer because it feels a lot more direct and honest but theoretically can’t take high rpm. I‘d keep with the DG especially since it’s practically brand new and definitely stay away from the BW 35, 65, 66.

Generally agree, but keep in mind that in the USA the XJ6 series 3 used the BW66 but it was mated to a 2.88 final drive that in my opinion took a toll on the gearbox. Earlier cars IIRC used a 3.30 ratio. These were 4000 pound cars, with the 4.2 liter engines, a 3.8 Mark II is a bit lighter and most those with automatics had 3.54 final drives. Jaguar knew there were excessive warranty issues with the BW65 and 66 but was not willing to re-engineer the car for the GM Turbo 350 or the heavy duty GM Turbo 400 as was fitted to the very heavy Daimler DS420 limos, at least the later ones. Everything came down to costs and money was scarce.

Fair enough, the S3 XJ I had was a 3.058 and the S1 is a 3.54 and lighter but there is a huge difference. Others won’t like the low stall but I do, it doesn’t just hang around at 2000 rpm in normal driving and reacts much more directly. If these had lock-up aka direct drive in top it would be even better. Sure the 350/400 would have been a great unit but the 66 generally worked well I guess.

Not sure about the BW 12 but the 8 is very smooth coming to a stop where you feel it with a 66 (very difficult to adjust just right and never perfect).
I‘d say the 12 would be the ideal transmission for any conversion because it’s vacuum operated. No linkage to mess around with.