Mine started with cold weather. As long as I shift slowly to third the first couple of shifts everything is fine.
Some on an Aussie site have speculated it has to do with the atf being too slippery for the syncro to get up to speed when it's cold.
Mine started when it got cold which is right after I installed a blower. I can always take it to the dealer but I'm pretty sure the Whipple will give them a good reason to say it's all my fault. Especially since I had to register the vin with FRPP to get the tuner. If that's the case there is a company in FL that sells rebuilt 3650's rated for 750 HP with a 26 spline input shaft for $1650. The more I think about it that's the direction I'm going anyway. When the clutch goes I'm swapping the
tranny.