hey all, i'm posting for my buddy here...he has a near mint condition 86 Trans Am...it has a LB9 TPI 305 and an automatic. the engine has about 60k miles and the transmission has less than that.

ok, here's a little background/lead-up to the problem. car sits in a garage 90% of it's life...in fact, the 60k miles have been put on over the past 15 years. anyhow, last week my buddy decided to take it back to his HS reunion in Great Falls, MT...from Graham, WA...about 650 miles. car did great the whole way there, didn't miss a beat and got about 22-23 MPG. after he got to Great Falls, he noticed the oil pressure gauge was kinda fluctuating. still holding specification pressure, but shaking a bit. checked the oil and there was NONE ON THE DIPSTICK. it was full when he left.

now, i will say this, the car leaks from a few places that i see...oil pan, rear main, valve covers...but i've had F-bodies in the past that leaked like this and they didn't go through this much oil. ok, on the trip back to WA, we topped it off with oil and all the way back to Spokane it held 45-55 PSI of oil pressure while cruising and about 35-40 at idle...it was doing great. checked the oil at each fill up and it was great.

come over Snoqualmie Pass and the car still seemed to do great, but we got back to town and the pressure gauge was fluctuating again. stopped and checked the oil and it was at the add mark...it had used 2 quarts in about 250 or so miles. look on the back of the car and there's black dust (oil mixed with road dirt). now, all the way to Spokane there was no oil residue on the back of the car and no oil consumption. so it would appear when the car is pushed through some mountains, it pushes oil out the seals, and in mass amounts.

the car lets out a tiny puff of smoke on start up (typical GM valve seals) but NEVER smokes otherwise. runs pretty strong (for a peanut-cammed LB9, lol) and gets decent fuel mileage...

sorry for the novel, just wanted to include all the details...thanks for your time and please feel free to add any input you can provide...

 

does anyone have any clue about this issue?

 

Is the black dust strictly at the exhaust outlets, or across the whole rear? Did you look under the car to see if oil was sprayed all over the bottom?

 

Im thinking rear intake seal...

 

If it used 2 quarts in 250 miles and it wasnt smoking it definitley has a serious leak some were. Does it only leak when the car is running?

 

the oil dust was all over the back when it went through oil. and yes, oil is all over the underside...but my buddy claims its had these leaks for years. I will check the rear intake seal...I know the valve covers, oil pan and possibly rear main are leaking...thanks for all the input guys!!