Does anyone know what is above the front tranny pan on the passenger side of a 2000 Rodeo 2wd? This would be the large circle with the snap ring inside it. The seal is leaking like crazy. I didn't want to disassemble without knowing what it was first. Thanks

That would be called the accumulator piston. IIRC, it acts like a surge tank to control shift quality. It's common to have leaks from that area. It has to be pushed in to remove the snap ring. Most isuzu dealers are real familiar with fixing that as many of the 1998-2000ish 4L30E's had that problem. Fix it ASAP as running low on ATF will fry a 4L30E in no time!!
G/luck
Joel

If you are the orginal owner it is a free fix if you are under 120k.

Thanks guys,
I was able to get a apointment for tomorrow. Knowing what was wrong let me keep the dealer from trying to charge me. Which they tried until I was able to get the manager to agree the tranny was under warranty. Thanks again.