The 2015 ADAC GT Masters champion and son of three-times Le Mans 24 Hours winner Klaus set an unbeatable time of 8m09.469s with the only sub 8m10s lap of the decisive session.
Ludwig also posted an 8m10.406s effort that would have been good enough for pole in the car he shares with Bjorn Grossmann, Simon Trummer and Jonathan Hirschi.
BMW was widely expected to annex the fight for pole after the in-form Sheldon van der Linde, who won both Lausitzring DTM races last weekend, whisked his #98 Rowe Racing BMW to first in Top Qualifying 1 with an 8m11.039s lap.
But with the South African's teammate Nicky Catsburg at the wheel, the #98 BMW slipped to 13th in the timesheets with an 8m12.772s lap, 3.303s down on the flying Ludwig.
Augusto Farfus instead flew the flag for BMW in the sister #99 Rowe machine in which he'll be joined by Philipp Eng, Nick Yelloly and Connor De Phillippi, taking second with a lap of 8m10.640s.
Jordan Pepper took third in the Konrad Lamborghini Huracan he shares with Axcil Jefferies, Michele di Martino and Maximilian Hacklander, while Christopher Haase was fourth in the leading Audi from Car Collection ahead of the identical Phoenix machine of Jakub Giermaziak.
Pepper was the only driver who improved on his second flying lap, as a lost wheel for the True KTM of Ferdinand Stuck in the Hatzenbach area brought out a slow zone that hampered all the drivers who started early in top qualifying.
The leading Mercedes runner, Luca Stolz in the #12 HRT example, will start from eighth, while the leading Porsche driven by Nico Menzel in the #25 Huber car will start only ninth.
After a speeding offence on Thursday evening, when Kevin Estre was clocked at 137 km/h in a 120 km/h slow zone, the 2021 N24-winning Manthey Porsche will have to start from the back of the first starting group outside the top 60.
The #911 Estre shares with Michael Christensen, Fred Makowiecki and Laurens Vanthoor was withdrawn from Top Qualifying as a result.
Meanwhile, the Glickenhaus SCG004c of Felipe Fernandez Laser was unable to set a lap in Top Qualifying 1 due to a ride in water and oil temperature, so turned back into the pit lane after one lap on the Grand Prix circuit.
The 50th edition of the Nurburgring 24 Hours starts on Saturday afternoon at 16:00 CEST.
