I think i might have lost the rear main seal. It's a fresh motor, first oil change after break in, so the rear main was new.

First thing i did was check the the things i had removed (drain plug and oil filter) but neither of those are leaking. It has been running much higher than normal pressure since the oil change (~32-60 instead of 18-60, but still not higher than 60psi). I had switched to 10-30 synthetic and a Mobil one m1-111 filter, plus it has the mostly ineffective water pass oil cooler.

It's a shot in the dark, but is there a possibility that the new filter somehow contributed to this failure? It's really the only significant change that happened here, and i have never lost a rear main in such a short period of time as this before. The motor didn't see more than 5200 rpm throughout the 200 mile trip it was on, and the main went under light load at about 80... or maybe 90, but nothing like a 1st gear pull.

I'm worried there is another contributor to the failure here. Any advice?

the smog pump has not been removed, i've heard that can cause a leak. The temp never passed 190 so i would hope there is no issue with cracks.

 

Jack it up and have a look where the leak is coming from.

 

Happened to me tonight, and i just left from my garage(200 miles away now), Ill have to have a better look in the day. It didn't look like there was any oil above the bell housing. It seemed to be pouring every time i stopped. I was kinda hoping for rear intake leak, but the period of time it came out in and the volume lost, its definitely leaking pressurized oil. I noticed the leak because the oil pressure was down to 30 psi @ 4k rpm, doesn't meet the tens rule (10 psi per 1k rpm) so i knew something was up.

 

Rear main seals don't generally "blow" or become "lost".

Leaks won't cause a drop in oil pressure, unless they are TRULY MASSIVE; like, big enough to where all 5 quarts are on the floor within 20 seconds.

Sounds to me like you have 2 symptoms: oil pressure gauge reads low, and a pressurized oil leak.

One part can account for both symptoms: the oil pressure sending unit. Check it, or just change it out. It's cheeeeep and easy.

If the oil pressure is still low and you still have a leak, then you have 2 problems: a motor with a bottom end problem, and a leak. Sounds in that case like you have a genuine issue with the builder.

See my signature for helpful troubleshooting logic advice.

 

Alright. Went out this morning and topped it off(3.5 quarts were lost!). Its right back up to pressure, but still running higher pressure than it did before the oil change. It didnt seem to lose as much oil during city driving on the way to work as it was on the highway. Only a few drips this time as opposed to the 8 inch puddle it was developing before.
The motor is still running super smooth and there doenst seem to be any additional noises coming from it. I will be checking the oil pressure sending unit. I hope its not a bearing/crank alignment issue.
I left my truck and garage behind in San Antonio 200 miles away. Hell... maybe i need to get a rental for the week. ~$900 plus labor if it grendades or 200 for a rental seems like a no brainer.

I'm hoping the simple solution is that i overfilled it with oil and that combined with 90mph @ 3k = I'm dumb... but not completely out of luck.

 

This is a late model with 1 piece rear seal right?
Even if it is the seal leaking, don't panic. I've had one that leaked after a new seal was put in. (not by me)
Turned out that the seal was spinning in the aluminum plate that bolts to the back of the motor.
New plate, gasket, and seal and good as new. <$100 not counting pulling the tranny.

 

Ya, its a one piece rear main. Did you grab the aluminum plate from a salvage yard? I'm unsure of where i would buy one. What made you decide the plate needed to be replaced, just precautionary?Anything that would suggest i should replace the plate as well? I'm hoping its something along those lines.
It also occurred to me that i might have over filled it. I'm sure that could have pushed the main seal out as well.
I cut open the old oil filter and the filter that was on when everything went south and there is zero metal flake. That mostly suggests my rotating assembly and bearings are intact.

Thursday its getting a new rear main and a fresh Zoom kevlar clutch. $346 in labor... ouch. It would be free for me to do in an evening at home... Houston sucks.

 

I knew something was up since it had a seal put in it only a month earlier and was still leaking.
I pulled the plate to change the seal (since it's too easy and you don't have to risk marring the crank surface trying to pry out the seal). When I went to drive the seal out of the plate, I could push it out with my fingers and it was clear looking at the outside of the seal that it had been spinning with the crank.
We just picked up the plate, gasket and seal from the chevy dealer. It wasn't much money and, since it's in the PITA zone, go with OEM.