Saving Old Seagulls

The gearbox on my recently bought forty plus looks to contain a mix of grease and sand. Is there a quick way to flush it or will the end cap definitely be coming off?

I’d suggest a proper clean. Remove the front and scrape out all the crud. Then soak in paraffin to degrease, and remove all remains. Dry, check all parts, reassemble and fill up with 140 grade oil. Proper job.

Yeah I more or less realised it just after I wrote that. Sorry!

Proper job sounds good.