Doing ATF change at 208k miles, unknown previous change history. Old O-Ring broken, put in new O-Ring but unfortunately cut it (pressing, rotating and wiggling it in and all of sudden went clear like it went out of the channel on the other side), I guess the other side must be sharp. Have a box of Nitrile O-Rings from Harbor Freight. First one popped through also and has a cut on it. 2nd one went in more carefully so it doesn't slip all the way through this time. Took it out to inspect and no cuts and put it back in. Google suggest basic Nitrile O-Rings are rated to 250F and good for petroleum/hydraulic fluids. Better Nitrile O-Rings have slightly higher temperature rating and chemical resistance. Hydrogenated Nitrile O-Rings are the best rated to 350F. Think I'm okay or back to the dealer for another o-ring? All nearby deals says o-ring is not in stock and takes a week O-Ring Material Selection / Comparison Guide BTW, the transmission pan is very shallow and the entire cavity is where the oil pickup tube resides is probably filled with oil. I'm guessing an imperfect seal in this o-ring doesn't affect oil pickup. It just enable some oil bypassing the filter in front of the pickup tube. Given how easy this o-ring is to rip, I'm guessing there might be a number of them cut or ripped in cars thats being driven around. Either from original factory or during service. Keep in mind we drained nearly 5 quarts which would more than fill this cavity. Of course during operation, ATF pump would be working and ATF flowing but again, the cavity in the oil pickup area is tiny.
Just me, but personally, I would not trust a Harbor Freight part on something as critical as a vehicle transmission. To repair non-critical items around the house, sure, but a transmission, nope. Know, that I am no expert in this and though I am usually the first one to reach for a cheaper alternative, in this case I would spend the extra time and bucks to get the OEM.
Thanks Bob, l was guessing Prius's ATF temperature is pretty low. Most other cars I've worked on runs ATF cooler next to the coolant cooler so ATF temp seems to be around coolant temp (maybe slightly lower) in most conditions. This gets up close to 200F. From your chart, looks like plane old cheap Nitrile o-rings should be just fine
