700r4 question

[byeoficr]

I finally got the truck running this weekend after the p/o had it sit for 5 years. On the test drive I noticed the transmission seemed to be acting funny. The transmission felt like it was switching gears more than I thought it should OD would kick in around 30 MPH. My question is do you think dropping the pan and replacing the filter would help? The fluid has some wear on it but it is not burnt. but there were some particals in the fluid on the stick when I checked it. Do you think this may be some corrosion from sitting? Or should I start looking for a core to rebuild?
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