4L60E P0733: What It Means, Causes, and How to Fix It

P0733 is the generic OBD-II code for "Gear 3 Incorrect Ratio." On a 4L60E it is one of the most useful codes the PCM can set, because it names the gear that is slipping and, by extension, the clutch pack that is not holding. This article explains how the PCM decides the ratio is wrong, what actually fails in third gear on a 4L60E, the diagnosis order that separates a cheap fix from a rebuild, and which parts to buy when the transmission comes apart.

What P0733 means on a 4L60E

The PCM calculates gear ratio by comparing input speed to output speed. On the 4L60E the input side is engine RPM (or the input speed sensor on later units) and the output side is the vehicle speed sensor on the tailhousing. As OBD-Codes explains, engine speed is calculated against the transmission speed sensor to determine gear ratio and torque converter slip; if the calculated ratio does not match the value the PCM expects for the commanded gear, the code sets and the check engine light comes on. Third gear in a 4L60E is 1.00:1, so P0733 means the PCM commanded third and saw the input turning noticeably faster than the output should allow.

Typical symptoms, per Transmission Repair Cost Guide: check engine light, slipping under acceleration, a delayed or flared 2-3 shift, or the transmission refusing to go into third at all. Some vehicles will also fall into limp mode.

What is applied in third gear

The clutch application chart is the key to this code. In the 4L60E, first gear uses the forward clutch and low/reverse (via the low roller clutch), second adds the 2-4 band, third applies the 3-4 clutch with both shift solenoids off, and fourth keeps the 3-4 clutch on and re-applies the 2-4 band, per the application chart walk-through at Certified Transmission. The only element that comes on for the 2-3 shift is the 3-4 clutch. If third gear ratio is wrong, the 3-4 clutch is slipping, or the oil that applies it is not getting there at full pressure.

The 3-4 clutch is also the 4L60E's most notorious failure. Sonnax states that burnt 3-4 clutch packs are notoriously common in the 4L60/E family, and that low line pressure and leaks of 3rd gear oil are the root cause of most 3-4 slipping. The 3-4 hydraulic circuit is long and interconnected with the D4, forward clutch, 2nd clutch and 3rd accumulator circuits, so several small leaks can add up to enough pressure loss to let the clutch slip and burn.

Diagnosis order

1. Check fluid level and condition first. Every source lists low or contaminated fluid as a cause. If the fluid is low, top it and clear the code. If it is dark and smells burnt, the 3-4 clutch is already cooked and the rest of this list is confirmation.
2. Read all codes. P0733 by itself points at a mechanical or hydraulic slip. If it comes with shift solenoid codes (P0751 to P0758) or speed sensor codes, chase those first, because a bad sensor or solenoid signal can make the PCM see a ratio that is not really there.
3. Do the application-chart road test. Certified Transmission's method: at about 40 mph, manually downshift to second, then move the selector back to overdrive. If the transmission stays in second-gear ratio instead of achieving third and fourth, the 3-4 clutch is not holding, and the solenoids are proven good because the manual downshift worked.
4. Watch the scan tool. Compare commanded gear against calculated ratio and TCC slip while driving. A ratio that reads correct at light throttle and drifts under load is a clutch that is holding until pressure demand rises.
5. Line pressure test. Sonnax notes that even a perfect 3-4 circuit will slip if line pressure or actuator feed limit (AFL) pressure is low or unstable. A worn pressure regulator valve bore is the usual reason, and it will not fix itself with a clutch pack.

Causes, most likely first

• Burnt 3-4 clutch pack. The thin OE 3-4 backing plate flexes on apply, builds heat unevenly, and the frictions glaze. Raybestos adds that at engine speeds above 5500 RPM, residual oil behind the 3-4 piston centrifuges out and partially applies the clutch, so a high-revving engine drags the pack even when it is commanded off.
• Leaking input housing or input shaft seals. Sonnax lists a galled input housing bore, a leaking input housing checkball (it must pull 25 in-Hg on a vacuum test), a missing input-housing-to-forward-housing O-ring, and worn input shaft Teflon seal rings as common 3-4 oil leaks.
• Worn stator support bushings and sleeve. The input shaft rings ride inside the stator support. Worn bushings let the shaft wobble and the rings cannot contain the 3-4 apply oil.
• Low line pressure. Worn pressure regulator valve bore in the pump, weak EPC solenoid or a plugged filter.
• Shift solenoid or wiring fault. Less common with a standalone P0733, but a solenoid stuck in the wrong state gives the wrong gear and therefore the wrong ratio.
• Bad vehicle speed sensor signal. A cracked or dirty VSS reluctor can fake a ratio error. Rule it out with the scan tool before pulling the pan.

The fix

If the fluid is burnt or the road test shows the 3-4 clutch not holding, the fix is a rebuild of the input housing at minimum, and in practice a full overhaul, because clutch debris has already gone through the pump and valve body. Half measures (a solenoid, a fluid change, a bottle of additive) do not restore a glazed clutch pack.

Inside the input housing, set the 3-4 clutch up correctly. Raybestos specifies 8 frictions and 7 steels for the 1993-up 3-4 pack, a clearance of 0.050 inch plus or minus 0.005 between the pressure plate and first friction, and pre-soaked frictions with unmodified steels. Use a heavy-duty backing plate to stop the flex Sonnax identifies, install new load release springs (never leave them out), and size the input shaft Teflon rings with the proper tool rather than cutting them. Air-check the loaded drum before the transmission goes back together. If you only need the plates, the 4L60E High-Performance Friction Clutch Kit and the rest of the clutch pack collection cover the 4L60E and 4L65E.

Replace while you're in there

• Billet sun shell. The OE shell is the other classic 4L60E failure and it is out of the case when the input drum is out.
• Stator support bushings, front and rear, plus a vacuum test of the stator sleeve.
• Pressure regulator valve and boost valve if the pump bore shows wear.
• Shift solenoids and EPC solenoid on a high-mileage unit, since the pan is off. The 4L60E Shift Solenoid Kit 1998-2009 is the inexpensive insurance item.
• Filter, pan gasket, all seals and the 2-4 band. Full kits are in the rebuild kit collection.

Cost and effort framing

If P0733 turns out to be low fluid or a speed sensor, it is an hour and a small part. If it is the 3-4 clutch, budget for a master kit plus a sun shell and a weekend on the bench, or a shop rebuild. The mistake that costs the most is driving on a slipping third gear: every slip cycle glazes more friction material and sends more debris through the pump. For the broader diagnostic path, see 4L60E 3-4 clutch pack failure, rebuild and HD upgrade and 4L60E no 3rd or 4th: direct clutch diagnosis.

Frequently Asked Questions

Can I keep driving with P0733 on a 4L60E?

Not for long. The code means third gear is slipping, and every slip cycle burns the 3-4 clutch further and sends debris through the pump and valve body. Check the fluid immediately and stop driving if it is burnt.

Will a shift solenoid fix P0733?

Only if a solenoid code accompanies it or the scan tool shows the wrong gear being commanded. A standalone P0733 on a 4L60E is almost always the 3-4 clutch or the 3rd gear oil circuit, not the solenoid.

Which clutch pack is third gear on a 4L60E?

The 3-4 clutch. It applies for the 2-3 shift and stays on in fourth. Third gear is 1.00:1, so P0733 sets when the input turns faster than the output while third is commanded.

Sources

• P0733 Gear 3 Incorrect Ratio (OBD-Codes)
• P0733: Gear 3 Incorrect Ratio (Transmission Repair Cost Guide)
• Diagnose Using Application Charts (Certified Transmission)
• Attacking 4L60/E Burnt 3-4 Clutches with Confidence (Sonnax)
• 4L60E/4L65E 3-4 Performance Clutch Pack Install Guide (Raybestos Powertrain)