SD350Sam wrote:
Early 99's (Powerstroke on fender) had notoriously noisy converters that sounded like marbles in a coffee can, most noticeable at idle. I see the OP mentions 99 model year and how it seemed to run quieter after service. They also only had a dinky air/oil cooler and didn't run through the radiator, great at sped but absolutely undersized when pulling a grade.
I've added the 6.0 cooler (replacing an aftermarket that went on after the first tow) as was mentioned, and a deeper pan, and ignore the noise on the advice of the trans guy at the dealer. I know lots were replaced due to noise when there was no functional issue. So far so good at 130K, towing trailers and now our 1181. That said I've got a trans fund started for it.
As others mentioned hoe you get this straightened out and enjoy the rest of the summer.
This. I have a 99 as well and the torque converter was replaced under warranty 6 months after I owned the truck. It sounded awful. I also added an aftermarket transmission cooler and use synthetic fluid. I also have an aftermarket temp guage to monitor temps.