Good luck. It could be a Hurcles, St. Paul or any manufacturer. Back in the day dump beds were a dealer install and they used quite a few different brands. If it's a St. Paul the brand and model number will be on the top of the ram cylinder towards the back. Nothing on the pump. You can repack the input shaft on the pump and also on the ram. Use graphite impregnated packing rope or Teflon. I used the graphite rope that's been around for years. If there's a problem in the pump like a broken impeller you're probably out of luck finding parts.
