Ok, maybe some of the rest of you have run into this problem. My dad and I have twin matching 2005 F150 FX4 flare side extended cab trucks and I did an oil change on his truck. While checking all the fluids, I noticed that the rear axle fill plug had A LOT of metallic silver/gray sludge on the magnet part of the plug. Built up pretty thick I might add. His truck has 32,000 miles on it and when I checked my truck which has 19,000 miles, it has the same stuff only not as much of a build up. His truck was built June or July of 05 while mine was built Jan of 05. He called the dealer and they said that was normal wear of the gears and such and that is why the magnet is built into the fill plug.

Has anyone else ever had this problem?
Should I be concerned as it is potentially damaging the rear axle parts?
Should this be covered under warranty?

According to the owners manual, the gear oil in the rear axle is synthetic. I have never heard of synthetic gear oil or any type of synthetic oil causing this type of problem before.

Any help or insight would be greatly appreciated.

Thanks,

Brian

 

No need to worry. The build up is normal, It will always be there thru the life of the vehicle. The magnet is to gather most of the metal particles to keep it from the gears. It will become less and less as time goes on.

Synthetic oil is the best!

 

Ok, that to me is NOT normal as every vehicle I have ever owned and changed the differential and axle fluid, I have NEVER seen metalic sludge before. I have seen dirty gear oil (non synthetic) which might have a sparkle to it every now and then in the pan but nothing like this that I found on the plug. I even had a magnet on the inside of the cover for my Jeep CJ 7 I had and there was a thin film of metallic sludge but nothing that was the thickness of what a fairly new truck would have with the amount of miles that are on it.

If you had a magnetic drain plug on your oil pan and found that much of a metallic sludge build up, wouldn't you want to know WHERE that stuff was coming from???

My thought was that the dealership didn't want to know anything about it since the warranty is almost up and once the warranty is gone, "oh... your rear axle needs to be rebuilt".

To me, metallic sludge indicates there is a problem. Not that it would be a "normal" thing.

 

It is normal, both your rear end and transmission should have mangetic plugs that catch particles of metal so small that they would pass through the transmission filter anyway. They are pieces of metal measured on the micronic scale, nothing to be worried about. When they collect on the magnet, it seems like a sludge because the particles are magnetized to themself as well, making it seem like a thick paste. No big deal, clean it off, reinstall it.

The rear ends on these trucks do have synthetic oil, and I believe run on a 100,000 mile interval for the rear end. You really shouldnt need to change it before then.

 

this is normal every truck i work on has this just clean it off. at 30k i would be servicing
the front and rear diffs also the transfercase and trans.

 

Is this normal for only synthetic oil to happen with? In all the cars I have ever owned, 82 Datsun 280ZX turbo, 85 Jeep CJ7, 97 Ram 4x4, and this new truck plus my two antique cars (69 Charger and 70 El Camino SS 396) I have never seen this type of sludge. My charger rear axle just had to be rebuilt as it was making a growling noise when I let off the gas and I found a lot of metallic particles in the gear oil. Basically the gear oil looked like a dark brown metallic paint on a car. And that was cause the ring and pinion was set up too tight last year when I had a shop rebuild it.

My driveline has been doing some weird stuff that the dealer "couldn't find or said was normal". If you tap the gas at a light to inch up, the truck rolls forward then feels like someone hit the brakes as the truck seems to lock up. When I took a tech out for a ride, it did the same thing and he said it was normal. We got back to the dealership and he took out another similar truck for a ride with me and it did NOT do that feeling. Its almost like if the rotors are out of round and you let the brake off till it just grabs in the warped area but fine on other parts. This is not the case as my pedal does not pulsate like they normally would with warped rotors though so I figure it has to be somewhere in the driveline. This metallic sludge build up leads me to believe that there might be a problem inside the rear. Now when I checked the front differential, there was no metallic sludge, neither in the transfer case. So why would I only find this in the rear?

 

You could take it in and ask the dealer to check it out since the warranty is about up. That way, if you have an issue after the warranty you can atleast fall back on the fact that you suspected something and the dealer would not do anything.

 

I agree that it is normal... I have seen it on many vehicles, old and new.

Better for it to stick to your magnetized plug than build up in the bottom of the diff.

It has NOTHING to do with the type of lubricant in the diff, it is all small metal particles due to normal wear of the ring and pinion gears.