Hyundai XG350 T/C lock up.

[oggb]

AFAIK the transmission in this car is the same as was used in the Santa Fe and Sedona from the same approximate time period.

It has a tendency I find incredibly annoying -- it will lock the torque converter and "bog" the engine, dropping the RPM to around 1100 RPM at around ~40 MPH. This is typically an issue on hilly rural roads where I'm traveling at around 45 MPH and encounter a hill -- it will refuse to unlock the T/C or shift down until it is VERY obvious that the engine is unhappy about what's going on. Besides this the transmission shifts perfectly fine.

I've tried unhooking the battery and that hasn't helped. Currently has Maxlife ATF with around 30,000 hard miles on it -- plan to change it soon.

Is this the nature of the beast or is this one "special"?

 

[Klutch9]

That may just be how it is. My '08 Sedona with the 5-speed loves to always be in the highest gear possible. Many times this means dropping down to near 1,100 rpm around 40 mph. Many A/Ts have this scenario though. Less RPMs means better fuel economy, so they're programmed that way. It is quite annoying though. Ironically, the Sedona transmission has a very effective 'hill-hold' feature when going up a long steep grade.

 

[Klutch9]

EDIT: I meant a low gear hold instead of hill-hold.

 

[Brybo86]

Is there an overdrive button you can try to disable? Or can you just drop it down a gear?

 

[crazyoildude]

change the fluid and try reflashing the tcm

 

[SHOZ]

Try tapping the brake enough to just light the lights. It might unlock when in coasting mode.

 

[oggb]

Just wanted to update this thread.

Trans had Full Synthetic Maxlife Dex/Merc with around five years and 30,000 miles of city driving on it. This would've been the older Maxlife Dex/Merc that didn't list Mercon LV on the bottle.

Changed the fluid out with some new Maxlife and the trans shifts perfectly again.

Guess it just needed some new fluid.