I know this is an older thread but I am experiencing the very same issue. Just picked up a 2014 QX60, never shuddered when I test drove the car but sure enough a few days later ...BAD SHUDDER. Looked over the car head to toe, couldn't find anything, saw the open recall for tcm programming, brought it in and it got done. Dealer claimed the transfer case was causing the issue- $6100 lol. Funny thing is I got no shuddering after tcm reprogram driving it home. Pulled the drain plug on transfer case and oil is CLEAN- nothing on the magnets of any kind. Seriously doubt there is a transfer case problem. I want to say that although the problem is mostly solved with reprogram, I occasionally feel a slight shudder at low rpms. I think this is just going to be the deal with these, crappy design and problematic since it's inception.
IF YOU GET SHUDDERING!!! BRING CAR TO DEALER FOR TCM REPROGRAM RECALL!!
It may not solve it completely but it will be much better.
So, continuing to check this to see why I would get even a slight shudder at any speed, I found the real culprit!! Some dingbat Autozone parking lot street mechanic overfilled the damned CVT transmission by almost 1 gallon!
Going to give a quick guide her for any other QX60 owners who are experiencing these issues, hoping to save somebody else from headaches.
First, call the dealer, give them your vin, if there are any open recalls have them fix them. Obviosly the most important is the tcm firmware reprogramming. Impossible to further diagnose this issue without first confirming that you dont have the correct programming.
Next, do a cvt transmission service. Get the gasket and the cartridge filter off Amazon, together cost less than $40. Parts stores have generic CVT Fluid for approximately $40 a gallon, pickup 2. Helpful to have a scanner that will give you trans fluid temp but not absolutely necessary. Drain the fluid by removing the drain plug (measure how much fluid you removed for a starting point on refilling), drop the pan and clean the magnet thoroughly. Reinstall drainpan with a new gasket, don't overtighten the small bolts. Facing center of vehicle, pull the canister for cartridge filter off by removing the screws. Change the cartridge, clean the canister, install the new gasket/compression seal, reinstall canister. Again DON'T overtighten the screws. Now refill CVT Transmission from the top, the plastic dipstick cap comes off by inserting a tiny pick into the tab from the top. Insert same amount of CVT fluid that you drained. Start the vehicle and allow it to idle for a couple of minutes. Shift through all the gears one at the time allowing it to stay in each gear for 5 seconds. Drive around the block once, now park on a level surface and remove the overflow drain plug just to the left of the drainpan. If the car is approaching normal operating temp, that's about 105f trans fluid, let it drain from overflow cap until it's just a slight stream. If it's not running out, add some CVT fluid until it is. There are videos on how to do this, whether for Infiniti or Nissan. Procedure is the same.
Here are the parts for a 2014 QX60 AWD with 3.5 litre engine
Next let's check the differentials. I cannot stress this enough. The transfer case and rear differential use very tiny amounts of oil. It's IMPERATIVE that you keep these filled with fresh gear oil. Start with transfer case. Drain and refill with 80/W90. This is not synthetic. Make sure what you buy has the apigl5 rating. One litre will suffice. Don't take wheels or anything else off. Just lift the car on ramps or jackstands, remove both top and bottom drain/fill plugs with allen socket and refill til it pours out. Rear differntial is the same but uses 75/w90 synthetic apigl5 rated. Same procedure but you will need to drop spare tire to access refill plug. Now we have both transfer case and rear differential serviced.
There is a further issue with these vehicles that also manifests in a shudder. The rear electric coupling. There is a bulletin on this. If you have done all the above and still have shudders, vibrations, disconnect the pigtail for the electric coupler on the rear differential. Doing so turns the vehicle into a front wheel drive vehicle disabling the AWD. You will get an error on dash. Drive the vehicle, if shudder vibration is gone you have a bad electric rear coupler. They are available rebuilt on ebay for a few hundred dollars or $1600 from dealer. If problem remains, reconnect the pigtail to resume normal AWD operation.
If you have followed this guide, most likely you will have solved shudder issues or noticed metal shavings or grindings in either the CVT Transmission, Transfer case or rear differential. The component with metal grinding or shavings is most likely the culprit. If you didn't find any metal then you probably need a new transmission. Remember there are 2 versions, older version has an aluminum pan with fins, newer transmission has a regular metal pan flat - no fins.
Hope this helps out someone!!