1) Front brakes overhauled. Discs needed replacing soon after purchase due to slight grab due to warping when pulling up. This problem is common in 740s. Pads replaced at the same time. ($800 all genuine)
2) Some front suspension bushes replaced.
3) A variety of lights illuminated on the dash, but the problem was tricky to source. I thought it was simply the connections behind the dash, but eventually the car just stopped quite suddenly on a motorway! After a tow back to the mechanic, I discovered an electrical wire from the alternator to the battery had worn and was shorting out. I am expecting more wires to go soon as some of the wiring in the hot engine bay is getting brittle with age. Best to replace before they go. ($180 + $150 for the tow)
4) Catalytic converter just gave up. I am replacing the whole exhaust system as it appears to be on the way out. ($700 non-genuine)
5) Engine cross member cracks. This is VERY common to 740s, but must be fixed as it will eventually snap and is a BIG job to get replaced. Look at the curved joins on either side of the oil sump when on a hoist. I am having mine welded up for next to nothing by the muffler man today.
6) The gearbox and engine are both strong. The gear selector moves a little with power on acceleeration and breaking. I had some bushes/mounts replaced, but it made no difference. I'm going to let it be.
7) I changed the standard tape to a Kenwood CD player. This wasn't too hard and with patience, you can cut out the old player from the dash piece in order to fit the new one in neatly. It looks and sounds great. This is worth doing. Who listens to tapes anymore?
8) Idle problems. This is common to older 740s and difficult to trace. I replaced all the likely culprits myself (plugs, leads, air and fuel filters, distributor cap and rotor), then gave it to the mechanic twice. He replaced the air sensor and cleaned the throttle body. It is much better now, but $500 later, it is still not as smooth as previous when cold. I think some of the problem is related to the wiring harness, which has never been replaced; they have a bad reputation in the early models. Mine seems in good condition, but there is evenidence that it is getting brittle. Nevertheless, I wont be replacing it as the job is big. I have heard that post '88 models have a better quality harness, so I would suggest going for one of these if you are considering a 740.