The rev limiter in the fuel computer shuts the fuel off until the rpm drops, then turns it back on. This will shake the car pretty hard.

Lift your foot and let the tranny upshift -- if the problem goes away, it's the rev limiter.

You might want to change the fuel filters, though -- lack of fuel will cause a missfire, and that will cause the computer to shut the fuel off to the offending cylinders for a predetermined time, then attempt to deliver again. This will also cause surging.

You could also drive slower -- I doubt it's legal in north America to go as fast as you would be in third at 5000 rpm.....

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!