Massive oil leak in silverado 3500 454 after rear main seal already replaced where now?

Answer 1

Answer 1I don't know, but I think I can tell you how to find it.
1. Have the engine, bell housing and transmission steam cleaned until it is free of ALL grease, dirt, crud, etc. You want it to be "as clean as the day it was born," so to speak.
2. Then when you take it home park it on a clean [oil and grease free] LEVEL, flat, smooth section of driveway. If that's not possible, then get a large smooth, uncrimped piece of cardboard [like a section of dishwasher, clothes washer, clothes dryer, or refrigerator cardboard].
3. Place the sheet beneath your engine and transmission, and using sticks, bricks, anything, LEVEL the cardboard sheet, perfectly level. Ideally, both the vehicle and the cardboard sheet [called a "tell tale," or a "tattletale"] should be perfectly level to get the most accurate test. Don't move the cardboard around, always keep it in the same spot in relation to the engine.
4. Then, regularly, visually check the cardboard tattletale for drops of leaked oil. For very tiny, slow leaks overnight may not be long enough, but you say your leak is massive, so you should check it every 10 or 15 minutes for the first hour or two. Matter of fact, if the leak is truly massive, you may have some external oil "runs" or even drips by the time you get home.
5. When you can see some droplets of oil on the tattletale, using a bright light, check the engine precisely above the oil spots. When you spot the drip point on the lower part(s) of the engine, visually "trace" the track of the oil upward until it stops. You will then have found the point from which the oil is leaking out of the engine.
Do not quit on just the one spot, as there could be other drips/possible leaks, so continue your observations for a few days, and make careful note of precisely where an oil "run" terminates. On a clean, dry engine, you can use a wax pencil, or Crayon to draw a circle around the leak point.
Once you know WHERE the oil is comming from, you can then analyze that specific area to figure out WHAT is leaking.

• • • • • • Agreed. Gm trucks are notorious for the oil cooling lines leaking either at the site of the oil filter transition or at the cooler. Another good place to look.....