when i look through the fill hole in the diff, with a flash light the fluid looks clear but with brown film someplaces. is it water, what is it, should i change it anyways?

 

Stick your finger in there and get some. Maybe get a small hose and siphon some out. Good gear lube is usually honey color to light brown. If it has a lot of miles it might be dark. The key is to figure out how many miles or years is on the lube and how hard do you drive?

Most people recommend changing lube every 50,000 or less. It is supposedly good for 100,000 of "normal" driving but I wouldn't push it. I would also change it if the lube was older than say 5 years. Comeon it's cheap and you rarely have to do it. Be sure to check the condition of the fluid when it is in the drain pan. It can tell you a lot.

Heavy towing or desert heat can cause the lube to break down sooner so should be changed sooner.

Now if with your flashlight you see a kind of creamy white to brown sludge in the case then I would guess you have water in the diff and should change it very soon.

Good Luck,

Jim Henderson

 

My diff lube was the creamy colored stuff also and that was due to water in the diff. It is easy to replace the oil and you can also check it for excessive metal shavings and any other weird stuff. I go off road quite a bit and cross many streams and creeks so I change mine pretty regularly. By the way mine is the 8.8 rear end.

 

what would happen if i wouldn't change it for a while?

 

The lube in my Trak-Lok 8.8 was black and did not have the strong "smell" of gear oil. I was told that this was due to the Trak-Lok additive and friction plate material in the oil. No water was found when drained. The Dana 44 in front has the light honey color and strong odor.

 

If you let the oil sit too long it may cause rust in places you don't want it. I even think I have read that it may combine with other things and create acid, bad. Water is not a good lube so it should be removed at your earliest convenience. I have had friends who drove their vehicles many many miles with water/sludge in the engine or gear train and they had no catastrophic failure. This is something that kills things over time. Of course you could get unlucky and the water will be where you don't want it at the worst time and poof.

In my opinion and I am NOT an expert, I would change the fluid within the next couple weeks or so. preferably this week end. When you have things drained take a good look at the fluid and any metal or other flakes. Should be flakes maybe like a teaspoon of pepper at the bootm of the pan. Should not be any metal chunks bigger than a grain of rice. If you have a drain plug magnet, it is normal for it to have a light to medium fuzzy coat of silvery grey metal. No chunks.

If you can see a lot of sludge in the casing you might want to try to scrap as much of it out as you can get too. I would also probably recommend a fluid change a few thousand miles later to get rid of any residual water.

Good Luck,

Jim Henderson