I just changed my oil and noticed a leak coming from where the engine mounts to the tranny. My guess is that the rear main seal went bad.
Well now about 20miles after the oil change the engine is startinng to knock in the lower end. It is barely noticable in the cab but clearly heard under the truck. The noise seems to come from where the tranny attatches to the motor, could this be because of the rear main seal or another problem?

Edit: the engine needs two warm up for a minute before you can hear it.

 

Alright it is definitely coming from the engine, not the transmission. It sounds like piston slap but it takes one minute before it starts and the noise stil continues when the engine is fully warmed up. I had just changed my oil to Royal Purple from Mobil 1 Full Synthetic, it was probably two miles on the new oil when the noise started. I have since added a quart of Lucas Oil Stabilizer but have not noticed a change.

 

Oh the noise also goes away when you raise the rpm. The noise is noticable from idle up to 1700rpm.

 

Didn't the pushrod 4.0 engines have too short of a piston skirt or something causing a knock?

 

I hope so. Like the Triton V10.
Its kind of weird that would be starting now though.

 

drive it . if you only heard mine when i change the oil it sounds like a bomb waiting to go off. what weight oil you useing. i use 10-30

 

I had 5W30 Mobil one and switched to 5W30 Royal Purple. Now I have a Quart of Lucas Oil Stabilizer in there too which poured out like honey. So to be honest I don't know where the oil weight is right now. The lucas Seems to have quieted things down to to the level when it started, it had gotten much louder. I also have a bottle of lucas upper cylinder lubricant & injector cleaner in my gas tank, I doubt that this caused the problem. I'll run it as is then in a week i'll change the oil if it hasn't stopped. Royal Purple is supposed to be the slickest oil you can buy, I wonder if it loosened something up.

The noise is a constant clacking and it is too loud to tell where it is exactly coming from.

 

10w-30 mobil 1 and your knock will most likely go away.

Rich

 

I found out the problem was from the factory tollerances being too loose with the short skirts. It is called the ford marbeling problem and it is just piston slap. This happened because I drained my oil for too long. You are supposed to drain it quickly and put in the plug once the oil really stops flowing out of the pan, dont let the oil drip out. Also fully fill the oil filter before you put it on. I am going to run the lucas and royal purple for 500 miles then I will switch back to Mobil 1 5W-30 synthetic. The problem noise should go away in 2 weeks but that lucas stuff is no good.