I had this problem on my SD. It did this off and on a month or two. During that time I put in new shift bushings. I thought that fixed it then bam, complete failure of my B2 piston. Left me stuck.

Just throwing that out there. Hope it is only bushings.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles