About a year ago i had my differential fluid changed because it was foggy and muddy (I have my trusted mechanic check and change any fluid when he does an oil change). I just recently had my oil changed and when he checked the diff fluid it was foggy and muddy. I don't go offroading i just use my truck for hauling. I usually drive about 30 miles a day. I have a F150 2012 xlt 4x4 with 130,000 miles (the previous owner put 112,00 miles on it in 4 years). Any ideas on whats wrong?

 

I had a 2004 Dodge with a Cummins and the rear diff fluid got cloudy not to long after I changed it. The truck had about 100,000 miles on it when I bought it. It had a huge rear end in it and 20,000 miles after I changed it it looked like crap again. I'm not sure you get all the fluid out when you change it, plus the rear gets a lot more abuse than the front. When I did the front fluid on the Dodge, it still looked good.

 

When you say you had a huge rear end do you mean you got rear ended or that your truck bed weighs a lot. Also are you saying that the old diff fluid should be flushed and cleaned out better when i change it?

 

Bad choice of words, it almost sounds like I need to lose wieght. The rear differential in the truck was really big, Large center section and large axle tubes, which means it held quite a bit of fluid also.

 

water emulsion.

If you have a look at the front differential fluid on most 4x4 trucks, it is cloudy and murky like that. changes in temperature condense humidity in there and turn the oil into an oil/water emulsion. The only way to clear it out (without changing it very frequently) is to get the fluid temperature up above 200f and evaporate the water out. That's very hard to do on a front differential for most people.

I suspect the big differential on the 2004 cummins, with it's large capacity, didn't get up to a temperature that would burn off the water in the fluid and it looked murky again at 20k miles.

This seems somewhat normal and it's hard to pinpoint any failures that occur because of it.

 

Older model units had a high diff failure rate due to the vent tube routing and location allowing road debris and water to enter the case . You may want to check the location of the tube and replace the valve filter .