2004 Accent: Clicking Noise & Transmission P0734 Code
 

I have a 2004 Hyundai Accent with almost 130,000 miles on it. I was noticing a noise when going in reverse. A couple of days later when I was exiting off the highway, I heard a noise and then a clicking sound as I pressed the gas pedal. Later that day, the clicking became constant whenever the car would move forward. Finally while driving on a street, the car got stuck in a gear and then jumped as it switched gears. The engine light came on. I had it checked and the error code was "P0734: Fourth gear incorrect ratio" which I'm assuming is for an internal transmission failure. I'm taking it to a shop in the morning that specializes in import transmissions.

Is there any chance that it is something repairable without replacing the transmission? Is there anything I should know or be prepared for before taking it into the shop? Any advice on the best way to go about fixing the problem without enduring unnecessary costs would be much appreciated. Thanks!

Sounds like an internal failure to me as well. Have you ever services the transmission (replaced the fluid)?

Get ready to buy a new trans or to have your trans rebuilt. Be sure to take it to a place that knows Hyundai automatic transmissions. They require a specific trans fluid.

From HMAService
 

This is what hmaservice.com says about it:

P0734
DTC NO
DIAGNOSTIC ITEM
P0734
FOURTH GEAR SYSTEM
- MALFUNCTION -

DESCRIPTION
• If the value resulting from driving the PG-A output (input shaft rotation speed) by the 4th gear ratio does not match the PG-B output (output shaft rotation speed) after 4th gear is engaged, DTC P0734 is output.

TROUBLESHOOTING GUIDE
Detection condition
• Engine speed>400 rpm
• Transfer shaft speed >900 rpm
• Fluid temperture>60°C
• PCM senses a signal that does not fall into the preprogrammed parameters.
Possible cause
• PG-B
• Transfer driven gear
• End clutch retainer
• Kickdown brake
• End clutch
• Malfunction of pulse generator circuit
• Kickdown brake slippage
SYMPTOM
• Automatic transaxle will hold in 3rd gear (D) or 2nd gear (2, L) when code P0731, P0732, P0733, P0734 is output.
• Code P0717 or P0722 may also be set (pulse generator codes).
Check item
• Malfunction of pulse generator circuit
• Kickdown brake slippage

You could get lucky, and just need a new output speed sensor. Replaced from the outside.