CAT50D Rear wheel dustcap

Hi, I'm new to forklifts and I'm doing some long overdue maintenance on a CAT V50D. One thing's got me puzzled. I want to repack the rear wheel bearings but the dust caps aren't easy to remove. They don't have a raised lip I can get a screwdriver behind. They look like the sketch below. I've tried hydraulic gear clamps and a slide hammer but no go. They're in there tight. Any suggestions on how to get them off? I am thinking of welding on a nut for a slide hammer but that seems a bit drastic.

Malcolm

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CAT50D Rear wheel dustcap