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My friend was driving my truck and heard a pop. A cylinder started knocking badly and misfiring. I replaced the injectors and its running very nicely now. One of them was so loose, I could turn it by hand. The needle was also stuck open. I also replaced the vacuum modulator on the transmission.
I looked under the truck while pressing the accelerator and saw a stream of oil leak out from around the bellhousing, but only while the rpms are above idle. At idle and when shut off, there is no leak.
My friend's guess is the rear main seal.
Any opinions? Would a rear main seal pop when it fails?
If it is the rear main seal, what else should I replace while I've got it all apart?

The truck is a 1985 F250 RWD with the 6.9 and a C6.
 

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Since there is only about 10-12 psi oil pressure at idle, it possible that your seeing the leak when the rpm's are higher. Can't say I've ever heard a rear main "pop" but that doesn't mean it can't happen.

Since the transmission has to come out, I would change the front transmission seal. Other than that, there isn't anything you can't get to.
 

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My friend's guess is the rear main seal.
Any opinions?
First step is you don't guess, you get underneath it and determine where the oil is coming from then go from there.
 

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First step is you don't guess, you get underneath it and determine where the oil is coming from then go from there.

True dat!!!
 
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