1999 Isuzu Trooper

Transmission problem
1999 Isuzu Trooper 6 cyl Four Wheel Drive Automatic 102000 miles

once a week or so it shift hard, the manufacturer reccomends a trans service, @100000miles, what do you think its going on, I read on youe page that it is a sealed transmission and no fluid change is required.
please help.
S linblad
January 26, 2008.

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