I finally was able to drive the SD this weekend (total of 60 miles). Engine pulls strong (better after as much as it cost to rebuild it), tranny is good, steering and suspension are great. The only issue now is a thunk upon deceleration and acceleration while in motion. I raised the rear of the car, checked the differential rear bushing, double checked the tranny mount, engine mounts, flex discs and everything is fine. I then put the shifter into neutral, grabbed the drive line and spun it from side to side. I can turn it appx 1 inch or so before it engages the wheels. Pulled the filler plug, there is oil but it resembles metallic black paint (metal in the oil). So now I guess it's time to go diff shopping. It's a good excuse to put a 2.47:1 in and take advantage of the first gear start I guess. So on goes the saga..........I suspect that with the car being from Idaho to begin with that the previous previous owner (maybe further back?) got the vehicle stuck in the snow and sat there spinning the wheel (not too good on the diff). It's really just speculation since there's no for sure way to know what has happened to this car in the past. Either way, definitely some sort of abuse to cause the diff to start to fail at just over 171K. Has anyone else had problems with their diff early on?

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1982 300SD 180K, rebuilt engine
1973 450SLC Megasquirt
1990 Volvo 780 - 273k
1993 Volvo 240 Wagon - Scrap yard slumber

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