Catera Oil Leak - Engine oil or tranny oil

[mikescat1]

Have a '99 Catera with 97K miles. Recently repaired it for oil leaks in a number of areas. Now more oil leaks seemingly from the engine/transmission mating area (rear main seal?) - oil "drops forming on the two downward facing bolts on the front lip of the bell housing".

Now the transmission does not shift smoothly as it does before this leak. Also, it sometimes jerk.

Mechanic says its engine oil leak about the rear main seal and could be addressed either with an engine block sealer or replacing the rear main seal. I'm wondering though if the transmission oil is also not leaking or even the main leak in this case. Prior to this leak, the transmission was shifting smoothly without any problems.

[mikescat1]

Topped up the tranny fluid at the mechanics. It required about two quarts of fluid. Now the shifting is smoother but still some leakage about the bell housing.

wondering if a sealant additive would help in this case.