I replaced both outer front shaft seals and bearings about 3 months ago. I also took apart the front diff because 4x4 was not working. Fixed it, replaced fluid, rechecked fluid level and now it looks milky on my finger. I haven’t used the 4wd at all. Why would the fluid be milky??? I used master craft GL5 80w-90 gear lube. Did I use the wrong stuff? I have a 2000 4dr Blazer.

 

usually a vanilla milkshake looking fluid in a axle is a sign of water mixing in with the fluid. is your vent hose up and out of the way?

 

Do you mean the coolant overflow vent hose? It hangs down past the axle tube. How would water get in there? Thanks for any help.

 

No, he means the front differential vent. It should run from the diff up to the top, driver side of the radiator and have a little plastic cap or possibly a sponge on the end of it. If it is broken off or hanging down low, water can get into it when you drive.

 

Ok, i checked the correct vent hose and it is up next to the radiator, no damage on it and has a plastic cap. How else can water get into the front diff? And how much water would it possibly take to make the oil milky?

 

It doesn't take a lot of water to make the gear oil milky. There really aren't many other areas for water to get in that wouldn't also cause an oil leak.

I'd drain it back out and refill it again, then check it a week or two later. See how it looks then. Maybe flush it with some brake cleaner.

 

Thanks! I will do that soon. Is there gear lube you would recommend using? Instead of the Master craft GL5 80w-90. I noticed a small leak where the drive shaft goes into the front diff. Would water get in through there? Please excuse me if I have used the wrong terminology. I don’t have much experience with 4wd. I can fix what I can see is broken or leaking.

 

Anywhere that oil gets out, water can potentially get in. It isn't likely that a slow leak at a lip seal would allow water in unless you have been doing some river crossing lately.

I usually use Valvoline 75w90 synthetic in my vehicles, but there really isn't much behind that choice.

 

No river crossing at all. Not even much rain.Thank You for your replies and suggestion.

 

Update. Drained fluid, cleaned with brake cleaner, refilled gear lube. So far almost a month and still looks clean. “not milky” Thank You.