O ring at transmission fitting

I found an O ring at my transmission fitting (lower line) when I opened the fitting from the transmission. Does that O rig belongs there or ...?
2008 4.0

 

Just replaced those lines on my 09 but didn’t take the fittings out. Looks like it’s supposed to be there.

 

Thank you for the reply.
I am just curious, did you replaced only the hard lines, or you replaced the hoses too?

 

Just the hard lines, the hoses were still in good shape.

 

Yes, machined threads needs a separate means of sealing, O-rings, flares, or some other mechanical means. Pipe type threads OTOH use the actual threads being forced together tighter and tighter to create the seal. Any pipe sealer used is to fill imperfections and lubricate the threads.

 

Well, there is a crush washer there also. I am confused why there is an O ring on top of a crush washer. And now looking at the parts diagram, I see only an O ring and not a crush washer. Maybe previous owner just added a crush washer!!!

 

Some designs may use a crush washer to keep it from backing out as an O ring isn't going to do it. It may have been added and the reason why the 0 ring is leaking, there isn't enough pressure to ''squish'' it against the metal sealing surfaces properly. I expect the crush washer is actually of a larger diameter on the inside so it doesn't interfere with the outer diameter of the 0 ring, correct?

 

NO, crush washer is too fit that I can not even remove it. O ring sits right on the crush washer.
Also, I did not have any leak from this fitting. the only reason I removed it is the fact that I could not break loose the tube connection. So I cut the tube, remove the fitting from the transmission and then used a torch to open the remainder of the tube from the fitting.