Did you drain the torque converter? 3.5 qts. doesn't seem like quite enough for a fluid change, but that's on a 722.315. Don't precisely know about your 722.317. If it were me I'd drain ALL the fluid out again, since you replaced the filter & gasket already you might be OK with leaving that, but I'd find out the fluid capacity for your '87 and substitute one quart of that with Trans-X and see what happens. If there is a bowden cable I'd look at adjustment there also. Before I conclude that the transmission needs major work though I'd look at any mechanical linkage that could be malfunctioning first. Look at a stuck kickdown switch too.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)