W126 - 1991 300-SEL

Ran into a bit of bad luck yesterday doing something I've done many times - changing/refilling differential fluid.
Small, soft plastic end-piece on refill hose fell off into differential. I suspect it's laying in the bottom.

CD-Rom shows no gasket between end cover and rear axle housing. Instructions say to use a sealant compound. Is there one in particular that stands above all others? Thanks for your time.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

On an nonMB transmission, I had good luck with Permatex Blue RTV. Every car parts store has a label for it on the shelf, few ever have it in stock.

Sixto
91 300SE