I think it's a #7 torx... I have both metric & sae allen wrenches, I forget which one I used. Yeah, as Lou said, it's Leimbach's way of making their pumps tamper proof. Great idea Lou to use a small flat tip screwdriver.
All this talk about "push/pull" with two different rc machines reminds me of the radio interference problems you guys will likely have with rubbing metal surfaces of two different models together.
I had trouble with my KH dump trk & pup, had to add a wire screwed to the tongue on the pup with a female slide clip & screwed a flat piece of metal to the hitch plate on back of trk so the two pieces were permantly grounded all the time. Otherwise, the slop in the pintle hook & loop caused the trk to go crazy.
You may have to do add a grounding wire to your dozer/scraper Joe.
Whenever I get my own scraper functional, I was thinking I'll slide a piece of pvc tube over the rear push bar on scraper so when the dozer pushes, the pvc will act as an insulator between the metal models.