Oil Leak?

[pgackerman]

My wife found some black oil drops (~3) on the garage floor located near the rear driver's side.  Quickly thought, Aha! transmission.  But the oil in there is nice and oily colored - not black - and full.  My engine oil was recently changed and is still mostly clear.

What else is back there that might leak oil?

[Fierofool]

The distributor O-ring will allow oil to puddle then run down the transmission.  The other thing would be a leaking rear crankshaft seal or cam thrust plate gasket.  Both require pulling the transmission as they're behind the torque converter or flywheel. 

It's possible that you might have a leaking CV joint boot.  The heavy grease in there can have a small degree of liquefaction but it would probably be slung around onto the underbody as you drove. 

Take some sidewalk chalk and mark your wheels, and reach underneath and draw a line across, directly under the rear crossmember when you park it.  That will give you some idea of where it's dripping from without having to jack it up and crawl underneath. 

[GTRS Fiero]

3 drops low won't show on the dipstick.  What color are the drops?  How do they smell?

[pgackerman]

3 drops low won't show on the dipstick.  What color are the drops?  How do they smell?

Very black and like oil.  Slippery too.
Color doesn't match the transmission or engine oil.

[Roger]

Rear Main seal

[GTRS Fiero]

Looks as if one of the offers to drive a spare Fiero tomorrow will be accepted.

[Fierofool]

He would have to drive 75 miles past Memory Lane to get one of them. 

A few drops of oil isn't a bad leak.  Bring it to the museum tomorrow and we'll try to sort it out. 

[GTRS Fiero]

True, small leak, but I hate having to clean oil and the dirt it collects out of my bay.

[pgackerman]

Rear Main seal

Sounds like the voice of experience.

[Roger]

Yep.
I have a question tho... is the '86 V6 a 2 piece or 1 piece rear main seal? Would I have to drop the crank to install a new one?

[ron768]

The Pontiac shop manuals do not show or specify what the rear main seal is, the Haynes book says its a one piece. I checked all my engine blocks (85,86,87 2,8 V6 plus the 94 3.4 V6 ) and all have a one piece rear main oil seal

[pgackerman]

Is this a drop the transmission sort of job?   

Where is the oil coming from:  transmission or engine?

[Fierofool]

It is a drop the cradle job with an automatic.  Manual transmissions can be removed without dropping the cradle completely.  Transmission oil on a manual would be clear.  Red on an automatic.  Engine oil is usually black due to combustion contamination. 

I forgot to look when we were at Memory Lane, but you can determine if it's coming from the distributor easily enough.  You should be able to see a puddle of black oil at the base of the distributor or on a little depression near it, on the top of the transmission.  Sometimes the oil will follow the seam between the transmission and engine block and travel around to the bottom, making one think it's a rear seal leak.

If you aren't getting oil splatters on the rear fascia, then the leak isn't really bad. 

[pgackerman]

> "Transmission oil on a manual would be clear."

My manual uses 5W30 oil (or 10W30). 

[Fierofool]

Even with that, it wouldn't turn black. 

In the later years, GM changed their recommended lubricant to Synchromrsh Manual Transmission Fluid.  It's still 5 w 30, but has superior lubrication qualities and provides smoother operation.