* Engine: The size and type of engine (gasoline or diesel) dramatically impact towing capacity. A diesel W350 will tow considerably more than a gasoline-powered one.
* Axle Ratio: Higher axle ratios allow for greater towing power.
* Transmission: The type of transmission (manual or automatic) also affects towing capacity.
* Specific Configuration: Options like heavy-duty suspension packages and additional towing equipment will influence the maximum weight it can safely pull.
Therefore, there's no single answer. To find the exact towing capacity for a *specific* 1985 Dodge W350, you need to locate its original owner's manual or check the vehicle's sticker (often found on the driver's side doorjamb or glove compartment). This sticker will list the manufacturer's recommended towing capacity for that particular truck's configuration.
Without that information, you can only give a very broad range. It's safe to say a 1985 Dodge W350, especially a diesel model, could likely tow in the range of 8,000 to 15,000 pounds, but that's just an estimate. Always check the vehicle's documentation for the definitive answer.