w140 tranny slipping 4th
 

my father's 97 s280 started slipping in 4th gear... when i checked the tranny fluid it had a silvery look to it... kinda like metallic dust mixed in with the atf...
about a yr or less ago he had a ring/helical in the tranny(don't remember exactly) changed...
the metallic stuff may well have come from the breaking in of that particular gear... is this bad? could contaminated atf cause slipping? we're hoping a fluid and filter change would eliminate the slipping.