just took the wife's 1991 740 sedan (approx 165,000 miles) to the airport and noticed at highway speeds, significant wander - I had to continually adjust the steering to keep the car going in a straight line. It was a bit windy as well, which made the problem even worse.

Any ideas on the cause and how to diagnose?

thanks

These are good suggestions, but if the front end checks out ok, also check the rear end. I just replaced the panhard bushings at 140k (they were completely shot). That resolved the last bit of cross-wind wandering in my 740.

700 front bushings are notorious - and after all they are decades old!

Also check for worn tie rod ends and ball joints.

Maybe a stupid question, but, do you have enough air in your tires?

Over time, worn steering components may have allowed the toe-in adjustment to go slightly toe-out. You may need to crank it in a bit.

chk,the control rod bushins&ball joints.