Which is the best silicone gasket maker to use on differentials:

-Permatex High Temp Ultra Copper
-Permatex High Temp Red
-Permatex Ultra Black
-Other

 

I used the Black RTV, however my stepdad's F250 had the Red RTV on it when he bought it.

 

Actually, all will work equally good. I've sealed dozens of diffs at work with all the above. All of them have over 100,000 miles and don't leak.

 

I used the red of my last 4 diff servicing, never had a problem

 

I've used the blue stuff, had it off at LEAST 6 times. Zero leaks.

 

2500 and I haven't had any problems with the red so I'm sticking with it.

 

I use the blue stuff as well

I have also used red and that works the same

 

Well, I have always used the black, but I wanted to make sure that was a good choice. There is a really nice diff gear oil change write-up on another forum that recommneded using the copper. I also see a lot of differentials that have the red coming out around the bolts. I've never had any problem using black, but was just wondering what you all thought.

 

You don't need the red on the diffs. It's for high temp applications. The blue will work just fine.

 

i use blue or black, normally what ever i have lieing around. never had a problem.