burnstransport Posted December 11, 2009 Share Posted December 11, 2009 Hi everybody, I drive a 93 DM690SX with 58K rears. The rear-most differential LH side cover was weeping oil so I removed it, cleaned off the corrosion and replaced the O-ring. It still leaked (worse) so I replaced it with a new, "updated" cover from Mack which was made of some plastic composite. The parts guy and one of the mechanics both told me it will likely seal better than the older aluminum cover. Well after driving it into the city and getting oil nice and warm, guess what . . . . still leaking Is this a common problem, do I need to use RTV in addition to the O-ring? Also, what type oil does that need? The Mack mechanic said it takes 80/90 which is what I have refilled it with each time. Are these differentials prone to cracks? I looked closely where this cover goes and don't see any cracks, do I need to look elsewhere? Any advice is appreciated, this job seemed simple enough and now I'm pulling my hair out. Thanks - John Quote Link to comment Share on other sites More sharing options...
MACKS Posted December 12, 2009 Share Posted December 12, 2009 Are you sure the cover is leaking,can you see exactly were it's coming from,most times a leak develops where the carrier bolts to the housing,there are two bolts inside that loosen and cause it to leak,if that's the case you need to remove the side cover to get to them. Good Luck Quote Link to comment Share on other sites More sharing options...
burnstransport Posted December 12, 2009 Author Share Posted December 12, 2009 Are you sure the cover is leaking,can you see exactly were it's coming from,most times a leak develops where the carrier bolts to the housing,there are two bolts inside that loosen and cause it to leak,if that's the case you need to remove the side cover to get to them. Good LuckYes, I can see the drips forming along the bottom edge of the cover when the fluid is warm. Quote Link to comment Share on other sites More sharing options...
fifth wheel Posted December 12, 2009 Share Posted December 12, 2009 Putting sealant on the cover bolts should solve the problem. Quote Link to comment Share on other sites More sharing options...
HK Trucking Posted December 12, 2009 Share Posted December 12, 2009 Putting sealant on the cover bolts should solve the problem......And you should also put a film of silicone gasket sealer all around the O ring and on the face of the diff housing before installation.I have never put one of those on "dry" with no sealant.. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment Share on other sites More sharing options...
burnstransport Posted December 16, 2009 Author Share Posted December 16, 2009 Putting sealant on the cover bolts should solve the problem.Silicone sealant or thread sealant??? How about thread locker???? Quote Link to comment Share on other sites More sharing options...
HK Trucking Posted December 17, 2009 Share Posted December 17, 2009 Silicone sealant or thread sealant??? How about thread locker????Silicone form a gasket - otherwise known as the "blue shit", and do what I said and put some all around the O ring and on the face of the housing where the cover fits up against.If you put threadlocker on those bolts, you'll be sorry next time you have to remove the cover!. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment Share on other sites More sharing options...
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