Any of the gasser wagons have a dual-circuit pump that will fit, that would be the best course for a cheap fix.

The ASD is integrated with the ABS. I once asked my local indie about disabling the ASD on my 124 sedan when the special differential seized from lack of oil, he said it could not be done. Worth trying the bypass hose as a troubleshooting method. The ASD computer compares the rear axle speed to the front wheel speeds to detect wheel-spin, and then pressurizes that circuit to engage the hydraulic clutches in the differential to reduce wheel spin (lock up the axle so both wheels get equal power). If the ABS system is on the fritz, it may be causing the ASD system to engage when there is no wheel spin.

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC