2001 Hyundai Sonata 2.4L 4Cylinder Shifting problems

SOURCE: transmission/shifting 2001 Sante Fe - Hyundai

Sounds like you might have serious internal transmission problems.

As soon as you can, get someone with a code reader to plug in the vehicle and find out what the code is for the Check Engine light to come on. Might give you a better picture of what`s going on.

It could also (cross your fingers) be something more usual like a clogged transmission filter (located inside the pan), or shift solenoid.

By the way, have you checked the level, look & smell of your transmission fluid?

Level should be checked with the vehicle running, after passing it in all gear ranges on the shifter, and putting it back in park (Check it on "cold" or "hot" level depending on if it`s been driving for a while or not).

As for look and smell, it should be reddish and not smell burnt. Hard to describe the smell of burnt transmission fluid, but normal fluid does not smell too strongly, kind of sweet. Burnt oil is usually black and has a strong odor. If the oil is burnt you have internal damage to the transmission.

One piece of advice I give you is get it fixed as soon as possible because if you don`t already have serious internal transmission problems, the longer you wait, the more chances you have of getting some, to the point of the vehicle just refusing to move. And believe me, speaking from experience, the transition point from the symptoms you describe to total refusal to move and the need for a tow/transmission rebuild is not that long usually.

SOURCE: 3rd brake light

This is how i did it on my 2006 Sonata

1.) unplug the connector in the trunk (its a small white plug running up to the third light, there should be a small clip you squeeze).

2.) remove the 2 gold-colored screws from inside the trunk. They can be seen from the trunk. 1 is thru the larger square opening where the wire connects to the 3rd brake light. The 2nd is on the right side thru a small (screwdriver width) hole covered by a piece of foam tape stuff I had to punch me screwdriver through the foam to get to it.

3.) after removing the 2 screws, go inside the cabin and the brake light housing pops up.

4.) disconnect the bulb from the housing while inside the cabin (I had to do this with me two forefingers since the housing only pops up and inch or two).

5.) in the trunk remove the wire and bulb. (it's about 5 inches long. the wire from the connector to the bulb socket)

6.) reverse steps to install.

It is a pain and reqiuires a bit of time only because there isn't a lot of room to move around, but it beats taking it to the dealershio!

SOURCE: trans drops into 3rd gear won,t shift to 4th

DTC P0734 is "4th gear incorrect ratio" - that's your torque converter 'LOCK UP Clutch" It's worn out (or you're using the wrong Trans Fluid required by Hyundai - SPIII OR Both). The P1624 is simply the Trans Control Unit (computer) communicating to the Engine Control Module (ECM computer) MIL - on request signal to ECM = asking it to turn on "Check Engine" light. MIL = Malfunction Indicator Lamp. When the torque converter 'lock up" clutch slips or doesn't engage, the trans automatically returns to 3rd gear and stays there (it's called 'fail safe' mode) until you cycle the ignition key, then everything resets until the malfunction occurs again.
You'll need to have an AT (Automatic Transaxel) tester hooked up to verify this. Hyundai has a Service Bulletin specifically for "gear incorrect ratio' codes. If when you changed the trans fluid, was it done at a Hyundai Service Center? If not, someone may have installed the wrong fluid.