On a related note to this, is there any idea how long the 98/99 transmission might last if it's taken care of? We know the engine is solid but I've never had an automatic with this many miles on it. The PO did transmission flushes semi-regularly and I don't think he towed really. Just curious.
Plenty of early '100's chasing the half million mark on original drivetrains.
Interesting about the change in manufacturers noted here - the 2000 and 2001 Tundra also had a couple batches of bad transmissions in that range as well. The biggest cause of issues with these years was found to be people towing with overdrive on.
I run my '99 with OD off quite a bit in the mountains and always when towing. With a mechanical transmission pump the higher revs are a benefit due to more fluid moving out and back through the cooler.