Rear main seal leak on 1996 Tahoe 5.7

[redneck122]

While I agree, using a stop leak is never the best solution. But i've had customers who just couldnt afford to replace the seal.

Any auto parts store should have a few different brands. I've used one brand, i forget the name, but its an all white bottle that says "Rear main seal stop leak". It worked well for about two years, until the customer brought it back to replace the seal.

[Atrain1]

Please, don't use any stupid additives like "Stop Leak" (edit: Bars Leak, White Shepherd, etc. fall under the "stupid chit" category as well). It'll do more harm than good.
Do it the RIGHT way and replace the seal that's leaking. And before you write it off as your RMS, check everything to make sure it isn't something simpler like the oil pan gasket.

I have seen enough rear seals leaks to know what the symtoms are. It is unlikely it is the oil pan gasket with it being the newer style. It will not hurt the engine to put in an additive that helps soften the seal. It is not like adding stop leak to the cooling system, which I just replaced the radiator cause I had a leak in it. I also have the rear differential leaking now, it sucks every time I fix a leak another one springs.

[soldier-of-the-apocalypse]

theres a reall good aditive i use it works EVERY TIME its called elbow grease its only .99 cents at the school of hard knocks

[mcantar18c]

I have seen enough rear seals leaks to know what the symtoms are. It is unlikely it is the oil pan gasget with it being the newer style. It will not hurt the engine to put in an additive that helps soften the seal.

LOL, a 1911 sniper and the Chuck Norris of the car world. Impressive.
What are the symptoms? Lemme guess... lots of oil leaking down the back of your engine, right? Could easily be an oil pan gasket, and you won't know unless you crawl under there and actually look at it.
And yes, more often than not putting a leak-stopping additive into a system on a car (be it the cooling system, the A/C system, power steering, engine oil, etc.) hurts more than it helps.
But hey, its your vehicle, do what you like.

[jmg8550]

It could also be the valve cover gaskets, the intake manifold, oil pan, oil pressure sending unit, or distributor gasket. Just to name a few. I'd bet it's the intake manifold gasket at the back of the engine leaking down onto the transmission or through the bell housing. Very rarely in my 7 years as a general technician specializing on GM trucks have I seen rear main seals leak. It does happen, but not too often.

Intake manifolds on 5.7 liter engines are notorious for leaking both coolant and oil. Also, cylinder head gaskets can leak oil. You would be wise to check thoroughly where the oil is coming from before wasting time and money getting it repaired.

Just my .02 cents as a former auto mechanic.

[mcantar18c]

It could be the intake manifold, heads, valve covers, etc., but the OP didn't mention coolant in his oil or oil dripping down under the transmission, as it would if the leak were above the trans and dripped down onto it and ran back down the housing.

[Atrain1]

It could also be the valve cover gaskets, the intake manifold, oil pan, oil pressure sending unit, or distributor gasket. Just to name a few. I'd bet it's the intake manifold gasket at the back of the engine leaking down onto the transmission or through the bell housing. Very rarely in my 7 years as a general technician specializing on GM trucks have I seen rear main seals leak. It does happen, but not too often.

Intake manifolds on 5.7 liter engines are notorious for leaking both coolant and oil. Also, cylinder head gaskets can leak oil. You would be wise to check thoroughly where the oil is coming from before wasting time and money getting it repaired.

Just my .02 cents as a former auto mechanic.

I agree on the newer style small block it is very rare. I will check the possible leaks you have mentioned being that you are a Gm tech an know more about them then a pizza delivery boy. Thanks for your input I hope it is something else. I do not have much faith that it is anything else. It does only leak when it is running and oil is running out of the whole in the dust cover.

[jmg8550]

Coolant doesn't necessarily need to be in the oil for the intake to be leaking oil. The oil could be coming from the valley in between the cylinder heads. Also, oil will still drip straight down and through the bell housing and drain out of the drain hole in the flex plate cover. Got burned on that one once, had to do an intake for free.

You are right about oil running down the back of the trans too.

[Atrain1]

Coolant doesn't necessarily need to be in the oil for the intake to be leaking oil. The oil could be coming from the valley in between the cylinder heads. Also, oil will still drip straight down and through the bell housing and drain out of the drain hole in the flex plate cover. Got burned on that one once, had to do an intake for free.

You are right about oil running down the back of the trans too.

It sounds to me that mcantar18c knows just enough to be dangerous.

[Atrain1]

Here is a quick rundown of how I do my transmissions just cause I am at work and bored. I start at the rear of the vehicle I first remove the 4 11mm bolts from the drive shaft, remove drive shaft. I then start on the front drive shaft, I remove the 4 11mm bolts holding it to the front diff and then the 4 16mm bolts holding it to the t-case. I then start on the T-case, I take the 6 15mm bolts off holding it to the rear of the transmission. I remove the 2 electrical connections that control speedo and 4wd, now I pull the t-case and let the fluid drain into a pan once it has stopped I slowly remove it lowering it onto my chest and then rolling onto the ground usually to the left of me and set it aside. Now I remove the 4 18mm bolts holding the cross member in and remove that as well. now I take a 8mm combo wrench and remove the 2 8mm bolts holding the wiring harness to the trans. I then dissconnect the electricle from the trans. Now I am ready for the 6 15mm bolts holding on the dust cover and the 3 bolts holding the torque converter to the flywheel. now I get a 4 foot extension with a 14mm deep well socket so I can get up to the the bell housing bolts and nuts holding the heat shield for the starter wires and the bracket for the 2 fuel lines and the dipstick. Now I remove the 6 14mm BH bolts, some times 7 on newer vehicles. I now jack the transmission up a bit to break it away from the dowel pins pull it back slightly and slowly lower the jack, pull jack out from under trans and drag trans to the custom made stand we have for rebuilding them. It has been awhile since I have done one so please feel free to tell me if I am forgeting something and if you want I can go into detail about how I build a racing transmission, or a trans built for big tires or pulling heavy cargo or what ever you want.