P0730 — Incorrect gear ratio
What it means: Incorrect gear ratio.
How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.
Check first: Check fluid level and condition
Don't risk it — look up listed providers near you and give them this code when you call.
Listed providers nearest Salt Lake City, UT
Closest first. Tell them P0730 and what the truck is doing. RoadService.app lists these providers and does not employ them or carry out the repair.
- 0.0 mi away — based in Salt Lake City, UT · (801) 531-9256
- 0.0 mi away — based in Salt Lake City, UT · (385) 503-8084
- 0.0 mi away — based in Salt Lake City, UT · (385) 386-4700
What P0730 means
Incorrect gear ratio. Common causes: Worn clutches|Fluid level low|Solenoid stuck|Failed shift.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Worn clutches
- Fluid level low
- Solenoid stuck
- Failed shift
- Rebuilding transmission before checking fluid
First moves (roadside)
- Check fluid level and condition
- Solenoid resistance check
FAQ
Incorrect gear ratio. Common causes: Worn clutches|Fluid level low|Solenoid stuck|Failed shift.
Serious — Power derate likely — plan to stop soon.
The most common cause is: Worn clutches. Other possibilities include Fluid level low; Solenoid stuck; Failed shift; Rebuilding transmission before checking fluid.
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Related codes
Codes that commonly appear alongside P0730, or share the same subsystem.
- Main shaft speed erratic (SPN 160 FMI 2)
- Input shaft speed erratic (SPN 161 FMI 2)
- Transmission output retarder speed erratic (SPN 162 FMI 2)
- Trans oil temperature very high (SPN 177 FMI 0)
- Trans oil temperature voltage high (SPN 177 FMI 3)
- Trans oil temperature voltage low (SPN 177 FMI 4)
- Engine speed signal abnormal update rate (SPN 190 FMI 9)
- Transmission output shaft speed erratic (SPN 191 FMI 2)
Same symptom: Won't shift
Other codes that show up as a truck that won't take a gear or drops out of one.
- Transmission output retarder position erratic (SPN 2919 FMI 2) · Drivetrain & Transmission
- Retarder not responding (SPN 2920 FMI 7) · Drivetrain & Transmission
- Gear selection failure (SPN 749 FMI 7) · Drivetrain & Transmission
- Range shift signal erratic (SPN 753 FMI 2) · Drivetrain & Transmission
- Shift finger not moving to commanded position (SPN 787 FMI 7) · Drivetrain & Transmission
- Clutch actuator open circuit (SPN 788 FMI 5) · Drivetrain & Transmission
Find a mechanic or related guides
General diagnostic guidance for diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack and more). Not a substitute for a scan-tool diagnosis on your specific truck.