Has anyone felt a surging or bucking feeling when in Sport mode, 4a and about a 1/3 throttle accelerating through 2nd. 3rd and 4th gears? RPM's are anywhere from about 1700 - 3000. Its not during the gear changes but in the gears accelerating. I'm looking to take my 2018 in for service soon and want to mention this but looking to see what others feel. In Sport mode and 2 wheel mode its perfectly smooth and in normal or eco mode in 4a its also smooth. Seems to only do it in Sport 4a lower trans gears.
Hi all, just bringing this one back for an update of what I think resolved the bucking I was feeling in Sport mode 4a. At about the time I had the truck at the dealer for the 21B10 SW update, I also changed the transfer case fluid on my own with Mercon LV straight from the Ford dealer. I noticed the bucking feeling in mostly Sport mode 4a shortly after that. In 2 wheel drive it was perfectly smooth. I drove a lot more to tune into it and did notice on a very smooth road it was also there in all other 4a modes like Normal or Snow/Grass but not as pronounced as in Sport but when power was applied to the front wheel drive system. To me it then had to be something with the transfer case, front driveshaft, axles or IWE's. It was time to rotate the tires anyway so while they were off I checked the IWEs and for sure they were locked without vacuum with no play or issues. I checked the vent to each and applied vacuum and they operated with no issues and no clogged vents. Check valve was checked and vacuum tested as well as the lines from the valve to the IWEs and no problems. All tight and held vacuum The vacuum reservoir was also checked and no issues or leaks. Front axles were checked as well and also tight when rotating and checking play at various positions. No play or problems with the front driveshaft so for the heck of it, I drained the transfer case again (fluid just changed 5000 miles ago) hoping to see something but the fluid was nice and clean so it was refilled with new Ford Mercon LV fluid (same as before). I thought I struck out and found nothing so continued to rotate the tires and brought a vacuum cap with me to take the truck for a spin and to lock the front IWEs into 4a (4wd) by disconnecting the vacuum line at the firewall solenoid and capping it with a vacuum cap in hopes of toggling the 4a and 2h buttons while driving to see if anything could be felt but after driving it, the shudder is now gone! Only thing I can think of is something was up with the original batch of fluid or one of the front tires has a shifted belt felt under load that was in the front or has a bad diameter compared to the rest throwing off the car in 4wd (tires rotated front to rear and no cross). Next is to check the loaded rolling diameter of all the tires but they all are of matching size and load rating 285 45 22 114h and are Pirelli Scorpion Verde's. They have only about 5000 miles on them so I'm kind of thinking this was something with the transfer case fluid and doubting the tires but will check the rolling diameters to be sure they match up. For now, I've been driving in 4a amazed this is gone then changing to 2h expecting to feel something under load in the rear but so far nothing. If we don't get too much snow this weekend, I'll be looking at the rear tires or swapping one back at a time to the front and see if this feeling returns up front but just happy I've tuned into a spot that the problem lies to further isolate or maybe fixed this. Hope these checks and details can maybe help others down the road.
