I noticed a small oil leak near the rear of my engine block and couldn't figure out where it was coming from. Took it to the dealer and they diagnosed a rear main seal leaking. When they had the trans out to replace the rear main, they also noticed a leak in the trans pump. What would cause these leaks? I only have 15000 miles on it and don't drive it hard. I do have a super chip, airaid fipk and magnaflow exhaust, sido. Would the chip have caused excessive crankcase pressure?

 

Just do a search under "Oil Leaks"...you are sure to find it. What year is your truck? If it is an early model 99, you might have the same problem that I had, and it was really the head gasket that was leaking. It was replaced once, and then started leaking agian, and then they just replaced the engine....but had to do a lot of complaining to get that done.
Hope this helps,
David

 

My truck is a 2000 4.6, and it wasn't leaking anywhere's else but the rear main, the dealer couldn't give me an answer as to why it went, so I can only speculate that the crankcase pressure went up. I'm curious as to why it went as I don't want a repeat.

 

My parents have a 1996 F250 with the 460 V8 in it, and the rear main started leaking at around 12,000 miles, because of what the dealership called poor quality, because there was a knick in the rear main gasket seal, they replaced it for free, under warranty.
That could have been the problem as well with yours. Well either way, good luck, hopefully the dealership that you bring your truck to is faster at their service than what the dealership that I bring my truck to is.
Ask them to see the gasket....IF you ask they have to show it to you. (Atleast they have to in Minnesota anyways.)