Ford Ranger P0735 — Gear 5 Incorrect Ratio Fault Explained

When your Ford Ranger shows the fault code P0735 – Gear 5 Incorrect Ratio. This means the transmission control module (TCM) is warning that the 5th-gear ratio it calculates from the input and output speed sensors does not match the expected factory value. In practical terms, this means the gearbox is slipping in 5th gear or failing to apply the correct clutch combination. It is one of the most common gear-ratio codes on Rangers. Rangers equipped with the 6R80 (2011–2018) and the later 10R80 (2019 onwards).

Understanding why the code appears and what it really means is the first step to getting the vehicle back to reliable operation. In most cases, P0735 is an early warning sign and can be fixed before it turns into a full rebuild — but only if it is diagnosed correctly.

What P0735 Means on a Ford Ranger

P0735 is an OBD-II standard fault. The TCM constantly compares the input shaft speed to the output shaft speed. It expects a precise gear ratio in each gear. When the vehicle is commanded into 5th gear but the measured ratio is off by more than a preset limit, the TCM flags P0735 and stores freeze-frame data.

On PX and PX2 Rangers (2011–2018), the gearbox is the 6R80 six-speed automatic. Fifth gear is an overdrive ratio (around 0.86:1), and it is achieved by applying the B clutch together with the E overdrive clutch. If either clutch is slipping or leaking pressure, the TCM will notice the ratio is wrong.

On the later PX3 Rangers (2019 onward), Ford switched to the 10R80 ten-speed automatic. It has closely spaced ratios, and fifth gear sits in the middle of the stack. Because the steps between gears are tight, even a small loss of clutch apply pressure is quickly detected by the TCM, which is why P0735 often appears together with other apply-time faults such as P2704 (Friction Element E Apply Time).

P0735 Symptoms You Will Notice

Drivers often feel a flare or a brief slip on the 4–5 upshift, especially under load. Sometimes there is a harsh shift or a delayed engagement. In many cases the check-engine light or the wrench symbol illuminates and the gearbox may enter a limited-function or “limp” mode to protect itself. On the 6R80, limp mode can default to a single fixed gear, which makes highway driving sluggish. On the 10R80 the TCM may inhibit the higher gears and lock the transmission to a reduced-range schedule.

If the problem is ignored, the slip generates heat and debris, leading to burnt clutch packs and cross-contamination of the valve body, turning what could have been a simple repair into a complete overhaul.

P0735 Why It Happens — Causes on 6R80 vs 10R80

The causes of P0735 differ slightly between the two transmissions.

In the 6R80, the most common reasons are fluid-related or hydraulic. Low fluid level, dirty fluid, or degraded friction modifiers reduce clutch apply capacity. A worn valve body or leaking seals can prevent the E overdrive clutch or the B clutch from applying firmly. Solenoid faults that mis-meter pressure to these circuits also lead to ratio errors. When the slip persists, the friction elements glaze or burn, reinforcing the cycle.

In the 10R80, field reports and technical bulletins consistently link P0735 to the E clutch. The ten-speed’s tighter ratio spacing makes it sensitive to small losses of apply pressure, so early stage E-clutch wear or a leaky piston seal shows up as a ratio error before the slip is even felt strongly by the driver. When the code is paired with P2704, it is a clear sign that the TCM has detected excessive time for the E clutch to engage.

How We Diagnose P0735 Properly

A correct diagnosis saves both time and money. At Brisbane Tuning & Turbo we start with a full scan. We use our Autel MS906 and HP Tuners suite to pull not only the code but also the freeze-frame data. We look at input and output shaft speeds, commanded gear, and actual gear ratio at the time the code set.

Next we perform a controlled road test or a dyno validation. This allows us to log live data for slip percentage in each gear.  Especially during the 4–5 shift and in steady-state 5th gear. We also review line-pressure readings and compare them to commanded pressure.

If the data indicates hydraulic loss, we then carry out line-pressure and clutch-apply tests to separate external control faults (such as solenoids or valve body) from internal mechanical issues (such as clutch packs or drums). On the 10R80, particular attention is paid to the E-clutch circuit.

This workflow ensures we replace or rebuild only what is proven to be at fault.

Fixes That Actually Work for P0735

On the 6R80, if the slip is caught early and the fluid is burnt but clutches are still intact, a fluid and filter service with a valve body re-seal or solenoid strategy update can be enough. If the slip has caused clutch degradation, the gearbox must be removed for internal repair or a full rebuild with new B and E clutch elements and seals. Any valve body wear identified during testing is addressed at the same time.

On the 10R80, most P0735 cases with a companion P2704 require E-clutch attention. This may mean replacing the clutch pack and piston and checking the drum and sealing rings for damage. If the issue is primarily hydraulic control, a valve body service or an updated solenoid body can restore proper apply pressure. Because the ten-speed uses adaptive learning, a re-learn or calibration update is performed after the mechanical fix.

In all cases, fluid quality and correct fill are critical. We always finish with a hot-check of level and a road or dyno validation to prove the ratio is back within spec.

Can I Keep Driving with P0735?

It is unwise to keep driving for long with this fault. A gearbox that slips in 5th gear generates heat that damages the fluid and spreads debris through the valve body. What begins as a mild slip that could have been fixed with minimal parts can become a burnt clutch and contaminated hydraulics in a matter of weeks. We recommend scheduling a professional diagnostic session as soon as the code appears.

Costs and Repair Time — What to Expect

For most customers the first step is a diagnostic scan and data-logged road test, which is usually a same-day service. If the problem is limited to fluid quality or valve body control, the repair can often be turned around within two days. A full clutch repair or rebuild will require more time. We provide a firm written estimate after we have test data in hand.  The required work can range from a moderate-cost service to a more involved rebuild, depending on what we find.

Book a Scan and Dyno Validation at Brisbane Tuning & Turbo 

P0735 is one of those codes where proper testing saves you from guesswork and unnecessary part swapping. If your Ranger has set this fault or is showing symptoms such as slip on the 4–5 shift, harsh engagements, or limp-mode behaviour, book a diagnostic session with our team. We will scan, road-test or dyno-validate, and give you a clear plan for either a targeted hydraulic repair or a full internal rebuild if needed.

Our workshop specialises in 6R80 and 10R80 transmissions as part of the Redorq TQ+ program. We also offer transmission thermal-management upgrades. Our workshop offers validated valve body solutions, so you can fix the fault and protect your gearbox for the long term.