Twscarp

Hi, new here, in July bought a 08 1500 Express 4.3 cargo van in south Florida, drove it back up here to Cleveland, OH area. The van has 200,000 miles, but runs fine, did change the rear main seal, and oil pan gasket, water pump, hoses, plugs and wires though. Now that the weather is getting cooler, has dipped to high 30's, low 40's, in the morning with cold start, the van will slightly lurch backwards during startup in park, only in the cold start condition. I Googled it, found a TBS stating that was normal, not buying that. Any ideas?