I was looking at the OEM replacement from Bell Lexus but they have common failures. Is there another brand that the community has found holds up better? Is it common to add an aux trans cooler while doing the radiator job?

 

Not sure about "common failures" with the OEM units, but I would stay away from the many Chinese radiators that are now sold. I would just get a Denso which is the OEM supplier. You can shop around for a better price compared to the dealer. Denso 221-9263.

As far as a aux trans cooler, if you are towing this is a good idea and the OEM setup is the way to go. Search for the OEM cooler installation thread here on the forum.