OBD-II Code
P0729
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$450–$4,800
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P0729 sets when the TCM calculates that input shaft speed divided by output shaft speed in commanded 6th gear falls outside the expected ratio window (typically a 10-15% tolerance) for a calibrated number of samples.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP0729 sets when the TCM calculates that input shaft speed divided by output shaft speed in commanded 6th gear falls outside the expected ratio window…
P0729 sets when the TCM calculates that input shaft speed divided by output shaft speed in commanded 6th gear falls outside the expected ratio window (typically a 10-15% tolerance) for a calibrated number of samples.
Cheapest-first ladder
scan live data for input/output speed sensor signals in 6th gear and look for noise, dropouts, or implausible values before condemning hard parts; check transmission fluid level and condition on a level surface at operating temp (burnt smell or brown color is a finding by itself); pull the TCM for companion codes (P0700/P0717/P0722 reframe the diagnosis); inspect the internal wire harness/pass-through connector for fluid migration that wicks into the TCM. Caveat: a true ratio fault in 6th specifically usually points to a slipping clutch pack or a stuck shift valve for that gear, not a generic 'transmission failing' verdict, so do not authorize a rebuild on a P0729 alone without verifying the slip on a road test with the scan tool graphing both speeds.
Vehicle-specific patterns2011-2015 Ford F-150 with the 6R80 commonly throws P0729 from a worn direct clutch pack and a cracked input drum, found on teardown after the scan to…
- 2011-2015Ford F-150 with the 6R80 commonly throws P0729 from a worn direct clutch pack and a cracked input drum, found on teardown after the scan tool shows 6th-gear slip rising with throttle.
- 2009-2014BMW 5/7 series with the ZF 6HP19/6HP26 sets P0729 when the mechatronic sleeve and adapter plate leak internally.
- 2007-2013Chevrolet Silverado 1500 with the 6L80 sets P0729 alongside harsh 5-6 shifts when the 3-5-Reverse wave plate fractures.
- 2010-2016Volvo XC60/XC70 with the Aisin AW TF-80SC develops sixth-gear slip from valve body bore wear, repairable with a Sonnax oversized pressure regulator and boost valve kit.
Estimated repair$450 to $4,800.
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