QuestionOwn a 2002 XG350L 3.5L with 74000 miles. Trans oil and filter changed at 30,000 miles (did not drain converter) The vehicle's transmission will shudder sometimes under the following conditions, this condition has occurred since the vehicle was new, never could be replicated in the shop:
1. Vehicle driven for a long distance at 65-75 mph at least a couple of hours.
2. Transmission will down shift (either for a grade or passing) to 4th gear and will hang in this gear for an extended period maybe a minute or two when it should have shifted back into overdrive.
3. Does not do this all the time but intermittent although it will do it more the longer the vehicle is driven.
AnswerI doubt the torque converter clutch is slipping, since this would likely set a trouble code which should be discovered easily on basic preliminary diagnostics.
One possibility is that the transmission fluid is getting too hot or that the fluid temperature sensor is reporting an erroneously high temperature. Under these conditions, the torque converter clutch will be turned off and the transmission possibly even shifted to another gear in order to increase the fluid flow through the transmission cooler.
Check your transmission fluid. It won't necessarily be red, but what you're looking for is a fruity odor and either a red or somewhat transparent brown color. If the fluid is brown and opaque, it may be time to replace the fluid again.
Additionally, if you used anything other than SPIII fluid during the last fluid change, flush the transmission with SPIII fluid. Hyundai had originally used Dexron in their earlier vehicles (1989 and older), but switched away from that due to torque converter shudder issues.
