Dishwasher loud noise

Dishwasher making loud noise. Found broken glass in bottom, removed pieces. Still noisy. How do I disassemble beyond the nut on the lower spray arm?

I could not find info on the given model number.
Please check it.
The following is for a GU980[COLOR=Blue]S[/COLOR]CGZO which I think yours probably is.

Here are the parts
Pump and motor replacement parts for WHIRLPOOL GU980SCGZ0 | AppliancePartsPros.com

Here is a tech sheet and a manual which should be helpful.
http://www.servicematters.com/docs/wiring/Tech%20Sheet%20-%208066008.pdf

https://secured.whirlpool.com/Service/SrvTechAdm.nsf/2cd44500d572193285256a45004fd9d6/56e33eb0e839a7fa85256a8e00510938/$FILE/4322430.pdf