P2905 moderate

Transmission Gear Ratio Error - Fifth Gear

The P2905 code means the vehicle's onboard diagnostic system has detected: Transmission Gear Ratio Error - Fifth Gear. This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $400 - $3,000 (parts and labor)

Check Your Fluid First

ANCEL AD310 OBD-II Scanner

Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.

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Read Transmission Codes

LAUNCH CRP123X (Reads All Systems)

Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.

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Common Symptoms

Fifth gear engagement issues
Transmission hunting between gears
Check Engine Light on
Engine RPM higher than normal at highway speed

Probable Causes (Ranked by Likelihood)

Fifth gear clutch pack wear Very High
4-5 shift valve problem High
Fluid pressure loss in overdrive circuit Moderate
Output speed sensor drift Low

Step-by-Step Diagnostic Procedure

Test fifth gear operation at highway speeds
Monitor 4-5 shift timing and quality
Check overdrive circuit pressure
Verify speed sensor accuracy

Frequently Asked Questions

What causes a gear ratio error?

A gear ratio error occurs when the TCM detects that the actual gear ratio (calculated from input and output speed sensors) does not match the expected ratio for the commanded gear. This can indicate clutch slippage, speed sensor issues, or internal mechanical failure.

Is this a transmission rebuild situation?

Not necessarily. While internal clutch failure requires major repair, this code can also be caused by speed sensor inaccuracy, low fluid, or valve body issues that are less costly to repair. Proper diagnosis is essential before assuming a rebuild is needed.

Can I continue driving with this code?

Driving with a gear ratio error is risky as the transmission may slip or shift unexpectedly. Have it diagnosed promptly to avoid further damage or a safety hazard.