I have a 2008 duramax. It’s lifted 6in on 35s and has 142k miles. It was completely stock until about 130k the filter plugged up on me towing my fifth wheel. At the time I didn’t have the cash sitting aside to properly “delete” it the way I wanted so to make things work I bought a mini Max tuner from my friend he never used it for 350 bucks and then I took a saws all to the exhaust I chopped it off before the cat . Not ideal but I need the truck for work. So aside from being really loud the truck does great. I’m getting 20mpg hwy and about 16 in town. So besides those two things everything is stock stock air, egr is still in place etc etc. I tow a lot with the truck I have a fifth wheel that’s probably 14k pounds and I run it all over the northwest. So I use the tow tune 60hp and I use the tow mode and manual when I run grades. Other wise if I am not running my trailer I leave it on street which is 120hp tune. I don’t do burnouts or boosted launches but I am not light footed. I always keep the maintenance up to date She is well cared for but is used as a truck. So I noticed that the truck hesitates between gears a little bit if your at WOT a lot more obvious in 120hp then 60!or stock. I looked into it and I know the truck from factory will defuel in the first gear or two so your not breaking stuff same with the tuner I read that if your truck has a stock trans the tuning will also defuel specially running a higher tune. And it’s a fairly generic tuner. So i let it go it’s never gotten any worse. I have only got one CEL ever and it was since I got the tuner it was a low rail pressure code after I was at WOT. Looked into it and I now know the truck needs a lift pump which can also help with the hesitation between gears I read a lot of guys thought their trans was screwed up but bought a lift pump and cleared the shifting up. so I have one ordered and I bought a fuel rail race plug and plan on porting out my fuel rail fitting to an 1/8th with 1/2 in fuel lines and a sump kit. So I know the fuel never be in short supply. Also have a 5in exhaust, down pipe and tip coming. So the truck runs great and that was the only issues I noticed until about a month ago. Now at wot it gets through the gears like normal fast and snappy besides the slight hesitation inbetween gears but when it gets to 4th and specifically 5th or when the tq converter locks in its got an obvious shake for a couple seconds in the transmissIon Doesn’t slip it keeps climbing through the gears till I let up. And then last night I noticed that At 60mph just cruising in 6th gear I give it throttle not wot but half petalish it kicks down into 5th locked up as it builds boost you feel the shake and then as it’s climbing 5th you can feel the tq converter lock up unlock lock up unlock until it goes into 6th. If I go from 1st and ease into the petal to wot I don’t feel the shake because the truck never locks up in 4th or 5th if your pinned. So basically this new shake is only at higher to full throttle when the tq converter is locked up. I believe I’m slipping my torque converter what do you guys think? also since the shake you can tell the hesitation is getting worse like the converter is having issues laying the power down could it be clutches or torque converter ? Never runs hot never ever shifts hard never limped. I am ordering a transgo today with a ppe deep vented pan and a ppe trans cooler because I tow a lot I’m also probably going to order efi live by motor ops with trans tunes. When I have the cash saved up hopefully in a month or two I’m planning on a ppe stage five build kit for trans and then updated trans tunes. Sorry for the novel I just wanted to be thourough. Anything helps.