Losing oil at rear of engine block of 2001 Isuzu Rodeo 2.2L 2 wheel drive what's wrong?

I have recently purchased a 2001 2.2L 2 wheel drive Isuzu Rodeo. It is losing oil at the rear of the engine block. What could be causing this. It has a part at the rear of the engine block that I can't identify in the Haynes repair manual. Where is the oil pump located?Losing oil at rear of engine block of 2001 Isuzu Rodeo 2.2L 2 wheel drive what's wrong?
bad rear main seal.
Rear main seal, not "hard" to change, but a pain. And, if that one's gone, the front one aint far behind, in fact it's "ahead" of the rear one.(sorry).But, oil has a way of migrating, and main seals usually last longer than oil pan gaskets, the only sure way to pinpoint an oil leak is to completely degrease the engine, and watch.

And, the oil pump is in the oil pan, well not actually "in" it but if you pull the pan, its right there.

The part at the rear of the block is the transmission, or could be the starter.Losing oil at rear of engine block of 2001 Isuzu Rodeo 2.2L 2 wheel drive what's wrong?
main seal, oil pan gasket, oil pressure sensor leak, intake or valve cover leak running down the rear of engine, oil filter/housing seal (if in rear location), you need to inspect for the leak. If not obvious, you may need to clean the residual oil to spot the leak.
oil pump will be at the front of the engine behind the crank pulleyLosing oil at rear of engine block of 2001 Isuzu Rodeo 2.2L 2 wheel drive what's wrong?
sounds like rear main seal going bad. oil pump is in the oil pan
need more information. where in the rear?
seal sound right