Front diff, Help!

I just bought a 2004 Z71 and I knew the front axle seals were bad. I prepped the truck today to replace them. The oil came out of the diff looking like a Black and Tan, so I guess there's been water intrusion. More disturbing was the amount of sludge on the drain plug magnet. Pic attached.

So at what point do I know I have to rebuild the front diff? I was thinking of flushing it with some extra 10w-30 I have laying around with some seafoam to dissolve remaking sludge and suck up any water still in there. Is that fine?

I have 2q of Lucas 80w-90 and some Lucas oil stabilizer to go in there once I replace the seals.

Dave

If it were me, I would just refill with some store brand, correct weight lube, after you get the new seals installed.

Drive around for a couple of weeks and replace with another fill of the same, checking the drain plug for more metal shavings.

Do that a couple of times until you get a clean drain.

Then fill with the correct weight lube of your choice.

No additives needed.

But it may be worth noting, a diff of that age and mileage, you could be getting close to a rebuild anyways and having run water soaked lube for no telling how long, certainly couldn't have helped the situation.

The front diff in my 2004 EXT was whining somewhat when I bought the truck with 116,000 miles on it.

When I had all of the fluids changed right after getting the truck, the fluid in mine was dark and not milky, but the drain plug had quite a bit of metal on it.

That is not uncommon with these diffs, as I have come to understand.

The whining in front diff continued to grow worse over time, so I finally had the front diff rebuilt.

Now, the whining has all but gone and when we check the fluid level at oil changes, the color remains good.

I just think trying to wash any gunk out with solvents and motor oil is probably not the best idea at this point.

Maybe setting aside a few bucks for a rebuild down the road would be a better idea.

Best of luck.

Thanks, I think I am going to combine the two methods. I filled it with 3oz of seafoam and 2 quarts of 10w-40 I had laying around and turned the axles over a few times by hand. I will drain it and replace the seals tomorrow. Then fill with cheap oil and do your method to make sure everything is out. The seafoam will absorb any residual moisture and break down sludge and then your method will clean it all out. it hard to hear if it's whining yet with the 33" Toyo MT's!

Sounds like a plan!

I only had 30 min yesterday and the driver side front axle won, couldn't knock it loose. I noticed the seal where the front driveshaft enters the differential may also be leaking. Can this be replaced with the differential still in the vehicle?

It is a do able job. Get a downloadable service manual. 

To sum up my experience, rent a slide hammer to have on hand. It cost me a $150 deposit at advance auto. Due to the front leveling kit, I couldn't get a straight shot at it. I used the chains from my engine hoist, bolted the flanges into the axle shaft, and then bolted the chain link into the snatch block that the hammer came with. 3 hits and it was out! Also, my pass side axle differed from youtube. The videos all show a c-clip inside a gear, but mine had a cir-clip on the actual axle. You can damage the thrust washers if you try to hammer that axle out.

While serving in the USAF in Alaska I winterized the vehicles of new arrivals. This is what I did:
Cleaned all oil pans and siliconed a heater pad to them. Put a battery heater UNDER tha battery because heat rises right? I installed TWO block heaters, one to use NOW and one to use after the FIRST one burned up. I changed the trans fluid to AMSOIL tranny fluid along with the power steering pump. I used Brake Clean to clean off the (and wheel bearings) differential, I tilted the rear axle (both ways) to drain out as much gear lube as I could and used AMSOIL gear lube to refill the pumpkin. I re-packed the wheel bearings with AMSOIL grease and never had a come back. All products were synthetic. If I ran out of Brake Clean I used lacquer thinner; after the first job I used lacquer thinner for all my cleaning jobs, it's cheap and does a good job. It evaporates fast enough to know it's long gone before I service what ever with oil.

dna9656 said:

While serving in the USAF in Alaska I winterized the vehicles of new arrivals. This is what I did:
Cleaned all oil pans and siliconed a heater pad to them. Put a battery heater UNDER tha battery because heat rises right? I installed TWO block heaters, one to use NOW and one to use after the FIRST one burned up. I changed the trans fluid to AMSOIL tranny fluid along with the power steering pump. I used Brake Clean to clean off the (and wheel bearings) differential, I tilted the rear axle (both ways) to drain out as much gear lube as I could and used AMSOIL gear lube to refill the pumpkin. I re-packed the wheel bearings with AMSOIL grease and never had a come back. All products were synthetic. If I ran out of Brake Clean I used lacquer thinner; after the first job I used lacquer thinner for all my cleaning jobs, it's cheap and does a good job. It evaporates fast enough to know it's long gone before I service what ever with oil.

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Sounds like my car back in the 80's.  I went to the University of Alaska Fairbanks in the late 80's and the car had an in-line block heater, magnetic pan heater, battery blanket and a disc heater inside the car.  Never had problems with the car starting.