Fault Family System: Powertrain (P-Codes) 13 SAE Codes

Gear Ratio Incorrect

Diagnostic & Technical Explanation

Code P0729 (Gear 6 Incorrect Ratio) sets when the TCM compares input and output shaft speeds during a specific gear (or any gear generally) and finds the actual ratio does not match the gear commanded, indicating the friction element for that gear is slipping or not fully applying. Causes are low or contaminated transmission fluid, a worn clutch pack/band for that gear, a faulty shift/pressure control solenoid, or a sticking valve body spool.

These 13 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 13 times.

Codes in this family (13)

Code	Definition	Repair coverage
P0729	Gear 6 Incorrect Ratio	4 ranked fixes
P0730	Incorrect Gear Ratio	4 ranked fixes
P0731	Gear 1 Incorrect Ratio	4 ranked fixes
P0732	Gear 2 Incorrect Ratio	4 ranked fixes
P0733	Gear 3 Incorrect Ratio	4 ranked fixes
P0734	Gear 4 Incorrect Ratio	4 ranked fixes
P0735	Gear 5 Incorrect Ratio	4 ranked fixes
P0736	Reverse Incorrect Ratio	4 ranked fixes
P076F	Gear 7 Incorrect Ratio	4 ranked fixes
P077F	Reverse 2 Incorrect Ratio	4 ranked fixes
P07D9	Gear 8 Incorrect Ratio	4 ranked fixes
P07F6	Gear 9 Incorrect Ratio	4 ranked fixes
P07F7	Gear 10 Incorrect Ratio	4 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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