what kinda silicone for the dif covers? and any tips to install it. eveytime i have done oil pans in the past they always leak i think i tighten the bolts to mush before the silicone seals?

 

I use the Permatex Black the last time, and it worked good. I have used the Red in the past with no issues either. Here is a write-up from another forum:

Materials Needed: Gear Oil of choice
One (1) Tube of Ultra Copper RTV Silicone ($3.98 @ Discount / Advanced Auto)
7oz-8oz of fricition modifier (as required for limited slip and posi)
Torque wrench
Razor blade
Catch pan

1- I washed the axle housing and cover with a scrub brush and car wash soap to minimize the dirt and or contaminents getting into the gears while I have the cover off, then I let dry for about 30 minutes.
2- I took the all the bolts but two out on the top but I did loosen them
3- with a pan to catch the gear oil under the rear differential I used a flat head screw driver to seperate the cover to the rear end. Becareful the rear end housing is aluminum and dont want to mar the gasket area up so it just takes minimal pressure to seperate the two pieces.
4- Once the cover is off I cleaned out the bottom of the Rear end housing with a clean rag, you will see a magnet in the center bottom and some metal shavings (that look like silver sand), clean them out,
5- then I took a razor blade and cleaned the RTV silicone off the housing and the diff cover, I never used any solvents but I did make sure everything was dry and clean with a clean rag after I was done.
6- Once both surfaces are clean you are ready to silicone and install the cover, just make sure to check and see if you have any old RTV (silicone) flakes on the gears and make sure there is no dirt or foreign matter in the gear area.
7- Now get some Permatex Ultra Copper ($3.98 at Discount/Advanced Auto & $4.99 @ Autozone) Cut the tube top to the first notch and sqweeze the tube around the cover and then going back around again and also looping around the holes.
8- Waiting a minute or two then putting the cover back on and securing it with two bolts, then putting a little RTV Silicone around the underside of the bolt heads that meet the cover and putting them on and tightening finger tight till you have all the bolts on, dont forget to put silicone on the first two you installed to hold the cover on,
9- then torque the bolts to 15 foot pounds then go over them again with 30 foot pounds crossing back and forth.
10- I waited just over One (1) hour before I added any fluid to give the RTV (silicone) a chance to cure,
11- Now comes the easy part refilling the oil cavity, If you have LSD you will need to put the additive in unless you are using Lucas oils which states on the bottle LSD additive not needed, then you fill with Gear oil of your choice that meets or exceeds GL5 requirments till it comes out of the hole where you are filling it (truck should be on level ground for this)
12- then put the black rubber cover back over the hole and road test, If you have LSD and have some chatter the manual states to do figures 8's to get the additive worked into the LSD. Good Luck.

 

i don't think it matters, as it doesn't get real hot like an engine does. i used black just because it didn't shine like blue or red. clean everything good with sandpaper or scotch pad and wipe clean with brake cleaner. put a liberal wide bead around diff cover, including around the bolt holes, let skin over according to directions for several minutes, then put it on and snug up bolts until silicon tries to squish out, then stop. let it dry for another hour or so while you do something else, then torque. if you squish it all out while wet it's less likely to seal.
lots of good tips here.... http://www.pavementsucks.com/tech/diff.php

edit... boy silver is fast today. beat me to it.