Sludge buildup on magnet (rear axle)

[Turbo_Bob]

After 9500 miles I replaced the stock rear cover with a Mag-Hitec cover. The stock magnet had just a little gray sludge on it, looked real good to me being this was brand new. The Dodge manual states with limited slip ( worm gear type ) no friction modifier needed and calls out for 75W-90 gear oil. So I used Mobil 1 synthetic 75W-90, also 7 quarts instead of 5 quarts because of the extra capacity of the cover. Well the cover did not seal up from day one so after 3 days and 592 miles and no towing I had time to fix the leak. Had a dent in the axle seating area and the O-ring could not seal it so I just applied some silicone to fix the leak. But here is the problem, when I removed the drain magnet it had alot of black sludge on it, alot more than the gray sludge I just wiped off three days ago. My feeling on this, Mobil 1 may not be doing the job of protecting the parts inside. I have used this oil in all my past rear axle's and VW race transmissions with none of this happening before. Is it the oil? Or is it because I lost 3/4 of a quart of oil in this time frame, still had more oil in there than stock, like 1-1/4 qts. more. API service code GL-5, Mack GO-G/S. Please help me with some info, thank you.

 

[SilverFox]

Don't worry, it's just a better magnet plus the small particles picking up aluminum oxide from the AL cover. The aluminum oxide gives the metal particles the dark color. I have the same thing and lots of it. You didn't hurt anything, it's perfectly normal. I have 10000 on my truck since installing the AL cover and I replaced the rear end oil with the Mopar GL-5 stuff.

 

[Turbo_Bob]

This black sludge is ferrious metal because after wipeing it onto a cloth I put the cloth close to the magnet and the cloth jumped to it. It is just so much more in three days than the last five months worth.

 

[RAMINSPEED]

Be sure NOT to use RTV silicone sealant with synthetic gear lube.

 

[johnmoore]

Originally posted by RAMINSPEED

Be sure NOT to use RTV silicone sealant with synthetic gear lube.

You mean it will eat through the silicone? I'm getting ready to install some FAST Coolers and will be using Pennzoil Synchromesh for the refill. Of course I already have a tube of Permatex Ultra Black Hi-temp RTV Silicone that I was going to use. If that is bad what should I use? Inquiring minds want to know.

 

[Prairie Dog]

I'm a little confused, I ran nothing but mobile-1 75-90 synthetic in my 93 and never had the silicone fail on the cover. I've also ran synthetic in several engines assembled with silicone and never had a problem. What experience has lead you to this conclusion Raminspeed?



Scotty

 

[Turbo_Bob]

The Fast Coolers come with a Mopar silicone to use with them. On my last truck with another Mag-Hitec cover it also leaked so I used silicone to seal it up and it lasted with the Mobil 1.