P0729 Gear 6 incorrect ratio

Sixth gear ratio error

P0729 in short

P0729 means the transmission computer compared input and output speeds in sixth gear and the ratio was off, which points to slipping. Low fluid, a worn clutch, a shift solenoid or valve body fault are usual causes. Get it checked soon, and stop driving if it slips badly.

In each gear the transmission computer expects a fixed relationship between input and output shaft speed. In sixth gear, if the measured ratio does not match, it sets P0729.

References list low or burnt fluid, a failed shift solenoid, sticking valve body parts, worn clutches and speed-sensor faults. Bulletins list the code for Toyota Tundra and Sequoia (C1 clutch damage), GM Silverado and Sierra (blocked valve body orifices), the Nissan Titan and the Kia Soul (6th gear synchronization error).

Start with fluid and bulletins, since a software update or fluid service is cheaper than internal work.

Most likely causes

  1. Low, old or wrong transmission fluid

    Common general cause
    Why it ranks here
    Reference pages list low or contaminated fluid among the first things to check for a gear ratio code.
    What would change this
    Rises if the fluid level is off, burnt or dark. Falls if it is full and clean.

  2. Bulletin-named internal fault (valve body orifices or C1 clutch)

    Supported by vehicle data
    Why it ranks here
    GM's PIP5100A for 2011-2014 Silverado and Sierra lists P0729 among codes on trucks that will not move and points to blocked valve body separator plate orifices. Toyota's T-SB-0170-09 lists P0729 for Tundra and Sequoia slipping from C1 clutch damage.
    What would change this
    Rises if your vehicle matches a bulletin and shows slipping or no movement. Falls if no bulletin applies.

  3. Shift solenoid or valve body fault

    Common general cause
    Why it ranks here
    Both references list a failed shift solenoid or a sticking valve body as likely causes of a gear ratio error.
    What would change this
    Rises if solenoid codes are stored or the problem is gear-specific. Falls if shifts are otherwise good.

  4. Worn clutches or internal damage

    Possible — needs testing
    Why it ranks here
    If slipping continues after fluid, software and solenoid checks, worn clutches are the next possibility.
    What would change this
    Rises if metal or clutch material is in the pan. Falls if the unit holds under load.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all codes and note any other gear-ratio, solenoid or speed-sensor codes.

    Low riskTool: scan tool

    • IfOther gear ratio codes (P0730 to P0735) are stored

      It meansSlipping is across several gears.

      Go to step 2

    • IfOnly P0729

      It meansThe fault is specific to 6th gear.

      Go to step 2

  2. Check fluid level, condition and any leaks, and ask a dealer about bulletins for your VIN.

    Low risk

  3. Have a shop watch live input and output speed and solenoid commands in sixth gear, and inspect the valve body.

    Best left to a shopTool: scan tool with live data

    Warning:Have a qualified shop do this step.

Symptoms

  • Slipping or engine flare between gears
  • Harsh or delayed shifts
  • Check engine light
  • Limp mode or no drive Gets more serious: stop and have it checked.

How to fix

  1. Check transmission fluid level and condition where the maker allows it, and ask a dealer about bulletins for your VIN.

Parts and cost context

  • Transmission control module (TCM):Bulletin repairs for this code are mechanical on the vehicles read, so a module is not the first part to replace. Labor varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Nissan

  • 2016–2017 · Titan

    Supported by vehicle data

    Nissan NTB16045 lists P0729 (6th gear incorrect ratio) among gear ratio DTCs on the 2016-2017 Titan and Titan XD. Whether the bulletin is still current is not verified.

  • NTB16045Status unverified

    Service information when P0729 to P0735 gear ratio DTCs are stored

    2016–2017titan · NHTSA 10192810

    Nissan service information for transmission incorrect-ratio DTCs on the 2016-2017 Titan and Titan XD.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • 2011–2014 · Silverado 1500

    Supported by vehicle data

    GM PIP5100A lists P0729 for no-move trucks and points to blocked valve body orifices. Whether the bulletin is still current is not verified.

  • PIP5100AStatus unverified

    Vehicle will not move forward or reverse; DTCs including P0729

    2011–2014silverado-1500 · NHTSA 10112391

    GM preliminary information that tells the technician to inspect the valve body separator plate orifices for blockage; the Sierra is covered too.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Toyota

  • 2007–2009 · Tundra

    Supported by vehicle data

    Toyota T-SB-0170-09 lists P0729 for slipping from C1 clutch damage on Tundra and Sequoia. Whether the bulletin is still current is not verified.

  • T-SB-0170-09Status unverified

    Slipping, MIL on with shift DTCs including P0729

    2007–2009tundra, sequoia · NHTSA 10032522

    Toyota bulletin attributing slipping or harsh shifts to damage to the C1 clutch assembly on Tundra and Sequoia.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Kia

  • 2014 · Soul

    Supported by vehicle data

    Kia PS289 lists P0729 as a 6th gear synchronization error on the 2014 Soul. Whether the bulletin is still current is not verified.

  • PS289Status unverified

    Shifting issues at low mileage, MIL on with P0729

    2014soul · NHTSA 10109717

    Kia notes P0729 as a 6th gear synchronization error, with P0734 and P0735, on some 2014 Soul vehicles.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0730Transmission gear ratio does not match the selected gear

    Same system Supported by vehicle data

    P0730 is the general incorrect gear ratio code and often appears with P0729.

  • P0735Gear 5 incorrect ratio

    Same system Possible — needs testing

    P0735 is the 5th-gear ratio error, so P0729 next to it points to slipping at higher gears.

All Transmission codes

P0729 questions

Can I drive with P0729?

Short, gentle trips to a shop are usually possible if it shifts normally. If it slips badly or enters limp mode, stop driving.

Is it always a rebuild?

No. Fluid, software and solenoids come first.

Sources and review

  1. OBD II error code P0729: Gear 6 Incorrect Ratio — PartsAvatar
  2. P0729 Trouble Code: Gear 6 Incorrect Ratio — TroubleCodes.net
  3. GM PIP5100A: no movement in forward or reverse, P0729 among codes — General Motors (via NHTSA flat file)
  4. Toyota T-SB-0170-09: slipping with P0766, P0729 and others — Toyota (via NHTSA flat file)
  5. Nissan NTB16045: transmission gear ratio DTCs including P0729 — Nissan (via NHTSA flat file)
  6. Kia PS289: shifting issues at low mileage, P0729 — Kia (via NHTSA flat file)
Last reviewed
Written by
Saurabh K.
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