i have a 98 gmc box truck c6500 series.medium to heavy duty truck,25ft.gas,automatic.iam having trouble with the park brake system.when i put in park,its does not engage in the park position right away.it starts to roll,but after a minute or two the brake system engages and locks into the park position.sometimes when i park it i have to keep my foot on the brake while it rolls and wait until the hydralic system engages and locks into park position.this does not happen all the time but it happens alot.also the other day the park brake warning light flicked on and off and then the park service went off and while i was in drive the truck locked up as i was driving.i had to shut off engine for 10 minutes,then restarted truck and everything was fine.

Optional Information:
1998 GMC c6500

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