Clunking with acceleration

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Ok guys I can't seem to figure out exactly what is wrong with my trike. It seems to have a clunk kinda of feel to it when I accelerate at a moderate rate. The noise seems to be coming from the drive chain area. Checking the slop in the chain it measures at 2.25". Before I go screwing something up, are there any suggestions?

I've already added more grease to the differential.

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This link has the pics of what I am looking at.

https://photos.app.goo.gl/atk7vwyhok3DdqMA8

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I figured it out. Turns out the chain was too loose. Tightened it up and the feel and sound have disappeared.