On my way home my truck started overheating as i was pulling in the driveway. I changed waterpump yesterday and now it runs fine on the freeway but heats up around town.

Cooling fan not working correctly. If you have a electric fan check relays to do this start vehicle and let run listen for fan this will be your low speed. If that works Rev vehicle and listen for the second fan to turn on if not you probably have a bad relay. If your fan is belt driven make sure it is working properly. The fan isn't spinning vast enough for town driving

Its probably because your fan isn't spinning at highway speeds. check your fan.

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