I'm getting a strange screech sound or squeal that starts at speeds around 60-70 mph and higher, never any slower.

As soon as I let off the throttle the sounds stops.

The sound does not start until I reach at least 60-70 mph, even if I am accelerating at full throttle. The sound is only at highway speeds.

I'm guessing either the IP or turbo may be involved. It is definitely engine related and not driveline.

Could it possibly be a pulley or belt on the front of the engine? I sounds similar to a slipping belt, but not like any other belt I've ever heard. Belts usually slip when first accelerating, not after reaching highway speed.

__________________
1987 300TDT
1981 VW MKI Caddy 1.6 diesel, waiting on engine swap
1983 D-50 Power Ram 4x4 "Mitsubishi" 2.3 turbo diesel
assorted gas powered crap and motorcycles

RIP: 1984 300TDT, 1982 300TDT, 1984 190D 2.2, 1992 300D 2.5, 1987 300TDT, 1982 Maxima LD28, 1983 Maxima LD28, Isuzu C223 P'ups X3, 1983 Holiday Rambler 6.2 Banks turbo diesel, 1984 Winnebago LeSharo 2.1 TD, 1985 Allegro 6.5