Did you try replacing the filter and trans fluid? Maybe its just debri in the filter.
Or try some trans 'cleaner' stuff to clean up the valves before you replace the fluid/filter.

valves could be sticking.

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
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1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD