Rear Diff Sealant, hard setting or soft setting?
 

I am currently re sealing my rear diff. I have here some Permatex silcone gasket sealer in both the hard setting and soft setting varienties.

Which one should I use, or does it not matter? I cant find anywhere here or in the FSM that says one way or the other. Just to use silcone gasket sealant.

Thanks,
dd

I am a fan of a very light coat of Hylomar HPF.

When I put the back cover on my diff I used a light coating of permatex copper (orange stuff). This worked well for me, I switch to the copper and seems to work very well.

I guess if you have to stock only one silicone sealant, the copper is the one. but it is designed to be used in high heat applications. rear dif would be fine with ultra blue, or black even.
John

thanks for the responses.

so im still a little confused...here are the sealants i have lying around...which one would you use? im leaning toward soft setting.

Hard setting:
http://www.permatex.com/products/automotive/automotive_gasketing/gasket_sealants/auto_Permatex_Form-A-Gasket_No_1_Sealant.htm

Soft Setting:
http://www.permatex.com/products/automotive/automotive_gasketing/gasket_sealants/auto_Permatex_Form-A-Gasket_No_2_Sealant.htm

I have some of this too:
http://www.permatex.com/products/automotive/automotive_gasketing/gasket_sealants/Permatex_Hi-Temp_RTV_Silicone_Gasket_Sealant.htm

dd

of those three, I would go with the last one.
the first two are gasket supplements. not replacements.
John
neither would be my choice though. I would go with permatex Ultra Blue. Ultra black is OK too, but the black you have will work, it's just not as good, so be SURE you have cleaned both surfaces REALLY well, I mean after scraping, and wire wheeling, rub really well with acetone. GET VERY CLEAN! and let the goop partially dry after you put it on the Diff cover. then assemble loosely, and only torque after setting overnight.

John

perfect - thank you. ill go out and grab the ultra blue variety tonight.

To further clarify, they're also not "silicone." I dunno if Mercedes have any bolt threads that go into areas with oil or coolant, but if so, #2 is a good choice to use on those threads.