It sounds like there's a pressure relief valve that is making some noise when the shocks extend fully and the pressure is getting bled off. I assume the noise is coming from the valve. I've not had that problem but it doesn't sound too serious. My problem with the SLS valve, and the reason I rebuilt it, was to eliminate the sagging rear end. Glad you solved the assembly problem. It's amazing how easy it is to get that cam reversed (and how often a 50-50 probability can go against you).

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold