My W126 was also squealing like a pig. Ditched the ATE's that were on the front and the Textar's that were on the back. Bought new pads from local MB dealer.
I realize that ATE/Textar may be OEM; nonetheless, new dealer pads have proven to be quieter.
1991 300-SEL - Model 126
M103 - SOHC
James Madison - Oppressors can tyrannize only when they achieve a standing army, an enslaved press, and a disarmed populace.
Liberty Firearms Training - After years of trying to regulate California criminals with a never ending stream of gun control laws they have still not given up with the belief that if they make something a crime that criminals will miraculously start obeying the law.