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Home >> GMC >> 1995 >> Forward Control 4.3 Z, Standard >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Automatic Transmission Diagnosis - 4L80-E >> Diagnostic Charts - Diesel >> DTC 85, Undefined Gear Ratio >> Diagnostic Aids

Diagnostic Aids

DTC 85 will set when an unknown gear ratio is detected for any gear but 4th. Note commanded gear and incorrect ratio. Check transmission fluid level. Compare scan tester gear ratio reading to specifications in GEAR RATIO  table.

GEAR RATIO

Gear Less Than More Than
1st 2.38 2.63
2nd 1.43 1.58
3rd .95 1.05
Reverse 1.97 2.17
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