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Hey All,
Done a new Monster clutch and magnum F not too long back. Didn't replace the rear main and cover bc it wasn't leaking. I went against my better judgement and said "If it isn't broke, don't fix it!" 500 Miles later, I had an oil leak and assumed a rear main bc it wasn't leaking prior. Pulled trans, clutch and rear cover replaced with new GM rear cover and seal. Used install tool and torqued to spec. Fired it up and........still leaking. Initially thought "Did I install rear housing and seal correctly?", although I knew I did. After researching here, found the Cam sensor is a problematic area of these LS1's. Ordered a new GM cam and oil pressure sensor. Pulled the FAST 92 and found neither of these an issue, still replaced. I did however find the rear knock sensor plug wet. Long story short, it was the rear valley grommet closest to the firewall at the bottom of the valley pan pushing oil up and threw. The seals were crispy and hard and with the high flow oil pump and synthetic oil, it was pushing up and threw, under the intake, and dripping down, around and through the bellhousing. Wanted to save some folk some time before they pull the trans and mis-diagnose as I did. Hope this helps someone......Thanks!
Funny you mention this, because I was planning to fix a rear main seal leak when I changed my slave cylinder, but when I pulled the transmission I saw no leak. I still have not bothered to see where my few drips from the back of the engine are coming from, but it is higher than the rear main and more in the middle than valve covers. Also not the oil pressure sender, so I may have the same problem. If it gets worse or I have occasion to pull the intake manifold I will check there.
It could also come from the valley cover. That valley cover seal will make oil run down the same area as the oil pressure sensor and cam sensor. I've had both the valley seal and knock sensor leak in the last few years. The knock sensor leak was so bad that oil was running down onto the headers. It made a smoke screen the whole way home. I had to stop and add oil a few times. My rear main seal was changed when the 4L80 got swapped in about 7 years ago. It has never leaked.
I got the Fel-Pro valley kit, although Fel-Pro calls it a manifold kit. While I was in there I tossed in new knocks and a harness. They were original and crispy also. Here is the part number:
07-16-2024, 10:11 PM
rear main leak not rear main leak 
