My KIA 99 NOT SHIFTING THE HIGH GEAR

Here are some possible reasons why your car is sluggish on takeoff and won't shift to high gear:

Low transmission fluid: If the fluid level is low, the transmission may not be able to engage properly. Check the fluid level and add more if necessary .
Worn-out oil seal: A worn-out oil seal can cause a fluid leak, which can prevent the transmission from shifting into high gear .
Faulty shift cable or shifter assembly: If the shift cable or shifter assembly is damaged or worn out, it can cause problems with shifting .
Clogged transmission filter: A clogged filter can restrict the flow of fluid and cause shifting problems .
It's recommended that you take your car to a mechanic for a proper diagnosis and repair. They can run an OBD scan to determine the exact issue and provide a solution.

just 1 possibility is this, Mercedes Benz Actros Replace gear sensor the other is you are just going to fast for the gear.

High or Low Upshift or Downshift Speed

High or Low Upshift or Downshift Speed
Checks

Cause

DEFINITION: An upshift or a downshift (or TCC apply) that occurs at a speed outside of the calibrated range. Refer to Shift Speed

ECM/PCM calibration information

Incorrect calibration in the ECM/PCM

Throttle position (TP) sensor

Misadjusted or faulty TP sensor

Faulty input speed sensor

Could be the transmission shift solenoids.
I've replaced dozens and so far, that was the problem every time.

May check fluid level and if low would more than likely indicate a leak. could also be a sensor that controls the shifting. does check engine light come on and if so,this could indicate a bad sensor.

Its reving high,like pressing on the fuel,and the RPM just shoots high,you are describing a sliupping transmission. Kia has problems with shift hesistation dealing with the TPS, get that troubleshooted first if its not the TPS you are dealing with a VSS(vehicle speed sensor ) if both component are not at fault the solution is another transmission or rebuilt

Hi,
The fluid has nothing to do w/ the shifting! The problem is internal and needed to replace those synchronizing gear! Better look for a used up tranny to install it in ur car!
thanks for using fixya!

you cannot run your truck normally in 4x4 low!!!! the low is designed to go slow slow.try shifting into neutral gear on column tap the high 4x4 then shift to reverse,back up 15feet then shift to drive.it should go into high 4x4 then if you want to go back to 2wheel high shift to neutral tap the 4x4 high until the light goes off,shift to reverse and back up 15feet then shift to drive and the 4wheel drive lights should all be off. then you'll be in 2x2 rear wheel drive. thank you for choosing fixya.com

No the fact that your vehicle is low on gas should have nothing to do with the shifting of the transmission. You are dealing with two separate issues.