Leaky 350 and TH350
 

I have a 69 C10 with a 350 engine and TH350 transmission that are both leaking fluid. I know the valve cover gaskets and trans pan gasket are both leaking, but it seems like there must be other leaks as well because ithe truck seems to leak oil while it's not running. What are some common areas that tend to leak on this engine/trans combo? I have a rear seal for the trans so I will replace that if necessary. Aslo, is it possible to change the oil pan gasket without lifting the engine?

Check the fuel pump gasket.
Also your front main seal may be leaking.
Mine is leaking from the front main seal and oil pan gasket. I do believe that you do have to lift the engine to change the oil pan gasket. If I am wrong I would like to know as I need to change mine myself.
Todd

You definitely have to raise the engine a few inches or so to get that oil pan out. A problem area in the oil pan is the corners of the front/rear seal rubber, get a tube of black permatex RTV to seal these areas, or buy a one piece oil pan gasket, but I believe you should still use sealant in those areas. Also check the oil pressure sending unit or line on the mechanical gauges.

Also check your timing cover, rear of the intake and distributor gasket. These also can leak!

It is probably dripping when shut off becouse the oil is all over the bottom and the wind is no longer blowing it further back on the chassis. It is very unlikely that the motor is actually leaking over night.