Two problems -

I apparently drained the wrong liquid - the bolt I pulled out was labeled with an "M" and the liquid was grey and did not resemble motor oil, although it had a few metal shavings in it. What did I drain? I need to go buy some of that liquid and replenish it

Where is the engine oil plug? This is my second time changing the oil and I can't ever remember where it is. Seems like they would label it.

Trucks in the workshop waiting on your answer before I can drive it again. Please help before work on Monday

 

Welcome to the Tahoe forum. Where to begin? Well starting at the front (4WD) is the differential which I think has a drain plug on the driver's side. Next is the engine crankcase which has the drain plug (13mm) on the psgr side. Then the tranny w/o a drain plug. Then the transfer case (4WD) which I'm not sure cuz never looked that close.

The oil drain plug does have a magnet tip so if you saw metal in the oil then it probably wasn't that. Also the crankcase is at the bottom of the engine. Also when you remove the oil drain plug, the oil initially shoots out about a foot which if you're not prepared for it, really makes a big mess. Hope this helps. If not, post a pic.

 

Well, it may be crankcase. I used 13mm to unscrew it, it was a bolt with a smaller tip on the end of the bolt. The liquid was kind of grey and greasy, definitely not motor oil. It was on the driver's side and the bolt had "M" on the end of it. If it was the crankcase, what would I put back into it and where?

 

Check the dip stick and see if the engine is empty. If it was the crank case that is the engine and refill it with 5w-30 motor oil

 

I'm not going to ask how you managed that! The liquid you're describing sounds like the transfer case fluid. As Shark said, the crankcase drain bolt is on the right side of the pan and for the uninitiated, leaves a mess on the shop floor the first time you attempt it.