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'96 Camaro V6 3.8 Erratic ENGINE FAILURE(former title Transmission Fluid in Oil: Effects on Engine?)

[1996 Chevrolet Camaro RS V6 3.8L 2-door coupe, 198,000 miles]
Transmission rebuilt a few years ago and rear main seal subsequently replaced. A few months ago, took to mechanic due to leaks.
Practically all major components replaced recently, including water pump, transcoolant lines, catalytic converter, oxygen sensors, fuel injector, fuel pump, ignition coil, belts, including timing belt, spark plugs, fuel filter, air filter, etc.
Found oil leak and took back to mechanic. He kept the car for a week, but found nothing. Both engine oil and transmission fluid continued leaking. (Needed to add 2 qts. oil.)
A couple weeks later, check gauges light came on at stoplight and engine died. On way home, died several more times while idling at stops. (Engine had not been run too low on oil, as it was being continually monitored and topped off.)
Mechanic now says needs new rear main seal and possibly bearings in engine.
Engine making clacking noises and breaking down-seems to be a rod. Car not driveable.
(Contamination of oil by transmission fluid had been based upon extremely thin consistency of the oil and possible subtle discoloration).
The sudden severe problem despite the recent extensive overhaul is not making sense. Along with sloppy actions such as neglecting to tighten a nut on the oil pan (not just inadequate tightening, but barely threading it on) have called into question whether anything was inadvertently done by the mechanics that led the rear main seal to fail again already or other components that would account for the symptoms.

Need a vehicle, so this is the only opportunity to look into these concerns/possible recourse before the car is sold and unavailable.
Impressed by the knowledge and involvement of the Cartalk community. Thanks a lot for your advice.

Model Year, mileage, engine size would be helpful… There is no way for transmission fluid to get into engine…Sounds like you ran it out of oil and destroyed the engine…

“A couple weeks later, check gauges light came on at stoplight and engine died. On way home, died several more times while idling at stops. Mechanic now says needs new rear main seal and possibly bearings in engine.”

“There is no way for transmission fluid to get into the engine.”

The only way I can think of is if the owner removed the engine oil cap and poured the transmission fluid into the engine, two quarts perhaps?

The car is a '96, V6 3.8L engine, 198K mi. The owner (me) did not mix the fluids-wondering if contamination mistake–or other oversight-- was made during repairs.

When the car died on the way home did you check the oil and was there any on the dipstick.

Why do you suspect transmission oil in motor?

I suspect Caddyman is right, however a main seal shouldn’t be leaking again, it sounds like i he crankshaft end was worn and should have been sleeved.

If your mechanic said the rear main seal failed and the vehicle was driven with the check gauges light on (oil?), a distance requiring it to be restarted several times it may be best to shop around for a remanufactured engine. “A few years” may be too long to claim an installation error on the rear main seal.

Yes, I checked the oil. I had been continually checking it and needing to add about a quart of oil over the past few day, so at the point when it died, it was 2 qts. low (and I added some more before continuing home), but that wasn’t the cause of the breakdown.

Suspected transmission oil in motor because expert interested Camaros noted the extreme thinness of the oil and possible subtle off-coloration.
BTW how often should a rear main seal go out on this vehicle?
How much should the rear main seal cost (parts+labor)?

You were leaking enough oil to be low 2 quarts and your mechanic “found nothing” - ?

This is all too confusing, but I’m guessing that your engine is just toast probably because you ran it dry. It may or may not be anyone’s fault if that’s what you want to know.

A friend of mine uses trans fluid in the crank case if he ever has reason to do an engine flush. Think of it as very high detergent, very low viscosity motor oil. I’m not saying to put it in a crank case or run it that way, but this wasn’t your problem.

Even if somehow ATF was introduced into the engine, up to say 50% ATF, that would not have damaged the engine unless it was over a prolonged period…

If the engine is knocking and clanging, replacing the rear main seal will not cure anything…There seems to be around 5 different things going on here…

Had the car at the shop for 3 separate times addressing the oil leaks. The second time, he said he drove it each day with pressure gauges on it without being able to detect any leak–yet when I got it home, it took me just 3 minutes to crawl under the car, locate leaks, and mark with Teflon tape for him.
Then (third time at shop), the leaks marked with the tape turned out to be what I was told was due to rear main seal needing replacement, as well as possibly engine bearings.
Can a real main seal go out that suddenly, when car had been running optimally?

In a 16 year old car with 200K on it, ANYTHING is possible…Cars don’t wear out one part at a time…The WHOLE PACKAGE wears out…Trying to repair it with band-aids is throwing good money after bad…

Never fall in love with something that can’t love you back…

RE: Oldtimer11’s comment: i he crankshaft end was worn and should have been sleeved

What would sleeving entail? Would/should that typically be done when the transmission is rebuilt? ?

Crankshaft “sleeving” does not exist except in peoples minds…Oversize bearings exist…As in engine overhaul.

Whenever the transmission is out the engine rear main seal should be replaced even if it’s not leaking. While the seal is out the surface on the crank journal where the seal rides should be checked for a wear groove because over time a rubber seal will eat into the steel crankshaft. The fix for this, short of a crank replacement, is a Speedi-Sleeve which is a thin stainless steel tube that fits over the end of the crankshaft journal and provides a new surface for the seal to ride on.

The complaint is still a bit murky to me and the engine oil appearing a bit thin and discolored is not due to transmission fluid unless it was put there by accident.
Thin weight oil, contaminated with engine coolant, or whatever, it’s impossible to say.

The 3.8 is a great engine but if this thing needs bearings then I would look for a good used motor as they’re quite common. Short of neglect, these engines should easily go 300k miles if maintained correctly.

Is it cheaper to rebuild or go with Jasper motor?
And how much should it cost?
Still wondering the reasonable cost for rear main seal (parts+labor).

3.8 what?? We still don’t know what car this is. There are st least 6 3.8’s I can think of off the top of my head. Each has it’s own quarks.

As far as I knew (all the info. necessary when ordering parts), the car is just a straight up
V6 3.6 L Camaro 2-door coupe.
It is definitely not a Z28.
If all the Camaro models had some letter designations, then it would be the RS, but again, I was only aware that it goes by just 2-door coupe.

Found some paperwork listing RS as the model:

1996 V6 3.8L Camaro RS 2-door coupe.

Missed the camaro part. Ok GM 3.8 great motor, if you have thin oil mist likely your intake is leaking antifreeze into the oil. That’s my guess at least, have you been loosing coolent at all??

Oooorrrrr how about this for a theory a leaky trans cooler (I belive it’s part if the rad in this car) forcing trans fluid into radiator at the same time antifreeze/trans fluid mix leaking from intake into motor. Boom watery tinted red oil. Long shot but possible.

It’s near impossible to be accurate with an estimate on costs as that can vary so much by locale, the shop and labor rate, etc, etc.
A Jasper engine would be cheaper than having a proper (key word) rebuild performed but I still think that if an engine is need the best route would be to find a used, low miles engine and install that.
There’s a dozen ways of rebuilding an engine with only one of them being the proper method. That means $.

The 3.8 in your Camaro should be a Buick engine. My oldest son has a '96 Camaro RS also, with about 250k miles on it and still running strong with 190 pounds of compression and ticking off 30 MPG on the open road.