Re: Bad turbo?
I doubt the turbo is the problem based on your codes. I would say you have more of an electrical issue with the F343 circuit. The U1424 is a Transmission code and really isn't that big of a deal, more of a communication error with the TCM and PCM. I would get to the bottom of the P0299 code which is your main issue and why you are in limp mode. I think your dealer is pretty clueless. I would have them check the wire harness and make sure the circuits associated with the turbo actuator is working properly.
The service manual says you don't have to drop the tranny to change the turbo, but it has you do quite a bit of weird stuff. Remove the exhaust manifolds, remove transmission cross member and push the transmission up to get the turbo to rotate forward to get more access to the turbo. Personally, when I put in my larger turbo I will be dropping the engine/drivetrain. I have gotten tired of laying over the engine, destroying my arms trying to reach all the difficult fasteners. I have done way too many turbo swaps on the WK CRD's and stopped a bit ago removing the turbo without droping the engine/drivetrain. I even made a little stand to hold the assembly as its really not that many bolts to remove the whole assembly. Plus watching it for years at the assembly plants I think its the way to go.
2014 WK2 EcoDiesel LTD, Trail Rated, GDE tune, Offroad Exhaust, 275/70/18 Duratracs
2008 WK CRD LTD - GDE ECO Tune, 3" Intercooler, CBE exhaust, GTB2260VKLR, 3.07 gears
2007 WK CRD LTD - Max output, GTB2265VKLR, Long travel, wilwood brake 6 piston front 4 rear