[DPM]

I too will be replacing the pumpkin on my 9" rear. Probably this weekend. I got a new (lower) gear set and a Tru Track limited slip. I asked this same question of Randy's Ring and Pinion http://www.ring-pinion.com/ where I bought the unit. Rats, why didn't the URL show up as a hyper-link? Sorry.

They said the silicone would be fine. You might want to check their site. They have some pretty good tech. info since randy writes a monthly magazine column for off-roaders.

 

[DPM]

If your rear is a new or rebuilt unit, you should break it in first to prevent damage from overheating. After driving it for the first 15 or 20 miles, it is best to stopand let the differential cool before proceeding. Maybe take a lunch break. Then return home.

After the first 500 miles, change the 90 wt. gear oil to remove any metal particles or phosphorous coating that has been losened from the gear during the beak-in / gear setting. During this first 500 miles, avoid overloading, heavy use or over heating.

Ford 9" rears can be difficult to fill completely with gear oil. Most 9" housings hold at least 3 quarts and sometimes as much as 5 quarts. Take your time and be sure that the oil has settled into all of the crevices.

Good luck and have fun!