LS "transmission squeal" issue..... Vacuum issue?
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Teching In
Joined: Feb 2016
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LS "transmission squeal" issue..... Vacuum issue? Hello folks I'm new to the LS world and have been working on my 1942 Dodge Pickup (budget rat rod) swapped on to a 67-72 C10 Chassis sporting a 2002 LR4 4.8l and a TH400. I have been scratching my head trying to figure out a transmission squeal that has plagued me since I started this build. The truck runs great, shifts great but once engine temp reaches 150ish degrees the what I thought was transmission creates a squeal. I thought it might be the transmission or converter purchased the one in the truck as a "rebuilt unit" off CL. I replaced the converter and transmission with a know working unit still the same noise and symptoms after. I've also pulled the belts to eliminate the accessory drive for any issues up there. My thought was well maybe converter clearance is off unfortunately I lost my shop space and had to store it this winter so my work time is limited. But as I'm sitting around on this cold NY winter day cleaning up inside running the vacuum cleaner a light bulb explodes in my head. I am running a carburator set up on this. I wasn't sure on how to route the nipples off the valve covers on the LS so I ran them into manifold vacuum. I'm thinking now I may have created a giant air compressor that is pushing air around the Main seal (or other seals) creating a squeal. I'm hoping someone can enlighten me on this and possibly a right way to route them. Also is this a common misconception on a beginner LS swap? I could test this by running it until the squeal comes on pull the oil cap or another major source to release built up pressure correct? Thank you all in advance for the help on this one.
The oil cap test will tell you if you're building crank case pressure for sure. PCV routing on the LS comes up in here from time to time. Probably the easiest fix is to get a LS6 Valley cover with built in PCV and then all you gotta do is run a line from the nipple on the valley cover to the intake and you can cap off the rest. Run a filtered vented breather on the oil fill cap. Simple and clean.
