Is There Anything Actually "Bad" With Having Moly Grease In Gear Oil?

[turbocruiser]

Hi folks,

I know the primary reason people say its bad to have the moly grease in the gear oil is that it shows some signs of inner axle seal failure...but...other than that, is there actually anything bad with having moly grease in gear oil...does it harm the gears, the diff, anything at all? The reason I ask about this is that I know for a fact I will get some grease in my oil after any axle rebuild; there is some small amount on the axle shaft itself as you slide it through the seal and in my case there is some small amount on the inner side of seal as well just in case I had to pull the shaft back a bit to align it, and because with me if some is good, more is better, I'll bet I've got a good amount of grease in the oil right now. I just wanted to wonder about this and get yer guidance. Thanks.

 

[alkaline747trio]

Grease doesn't protect against friction as well as oil, and your front axle will be VERY hot.

 

[turbocruiser]

Grease doesn't protect against friction as well as oil, and your front axle will be VERY hot.

Hmm, very interesting, so why not do the deal where the bearings and all assorted internals are in oil vs. grease. I think several makes manage things that way right??? So should I quickly drain that fresh fluid to rinse out any grease? Thanks again, I did not know that about grease.

 

[SteveH]

I wouldn't lose sleep over it - you might drain it one more time and refill with clean oil. My front diff has had moly grease contamination on a few occasions. The moly is a fine lubricant and certainly won't hurt the gears. The thicker viscosity due to grease contamination is what might make it run somewhat hotter.

The wiping action of the gears in a diff is much different than the rolling action of wheel bearings, birfield balls, etc. So, 90wt and grease, while both 'greases', have different properties for different reasons. Again - I think we (on this list) can obsess about oils and greases a bit. The key thing is to have it filled with the proper stuff and not have water contamination.

Steve

 

[cruiserdan]

Some molly is inevitable and is not a problem. As long as you don't have enough of it in there to make chocolate pudding you are not harming anything.

 

[e9999]

can't imagine it would hurt much either.
Although if you have a fair amount due to seal wear, I would also make sure there is enough in the knuckles.

 

[alkaline747trio]

When I got my 80, the inner axle seals were shot, but the PO decided they didn't want to fix it, so they filled the front diff with moly. The front diffhousing was HOT to the touch due to grease's innefficiency to displace heat, and the extra drag and friction that it added compared to diff fluid.