Sonnax BW-SD-4 inner damper springs are for the BW 310mm LU (Chrysler A618), 47RE and 48RE Cummins diesel. These springs replace worn and weak OEM springs that may have taken a set.
The much weaker .162" wire outer springs used in A618, 47RE dampers have long been know to bottom out in TC clutch engagement. This harsh clutch engagement may eventually cause the turbine shaft to break along with other transmission components. Chrysler upgraded to a larger .177" wire diameter outer spring on the 48RE. Although this spring has a 43% increased damper capacity over the earlier version, it is still prone to bottoming out, especially if the diesel engine is chipped or modified for greater torque.