Shop All Transmission Parts →
Cobalt Transmissions
| Model | Automatic | Manual |
|---|---|---|
| 2.2L and 2.4L Ecotec | 4T45E four-speed | Five-speed |
| SS supercharged (2005-2007) | None | Getrag five-speed |
| SS turbo (2008-2010) | None | Getrag five-speed |
The 4T45E is the heavier-duty version of the 4T40E, and it went into a long list of GM compacts and midsize cars of the same era: Cobalt, HHR, Malibu, G5, G6, Saturn Ion and Aura. That is good news for Cobalt owners, because parts are plentiful and every one of its failure modes is well documented. Confirm the unit with the RPO code (MN5 for the 4T45E) on the service parts label in the trunk.
Problem 1: Stuck in Third (Failsafe)
When the TCM loses trust in a speed sensor or a solenoid circuit, the 4T45E defaults to a fixed gear, typically third. The car pulls away slowly, will not upshift or downshift, and the check engine light is usually on. It feels catastrophic and often is not.
Read the codes first. Input or output speed sensor codes (P0715, P0720) point at the sensor or its connector. Shift solenoid codes (P0751, P0756) and circuit codes point at the solenoids or wiring. On a car with clean fluid and only electrical codes, the transmission itself is usually healthy. Our 4T40E/4T45E solenoid kit replaces the full set, which is the smart move on a high-mileage unit once the pan is down.
Problem 2: Harsh Shifts and P0748 or P1811
Brutally hard shifts at every change on a Cobalt usually mean the pressure control solenoid has failed and line pressure has defaulted to maximum. A P0748 or P1811 code is the clue. The opposite, soft and mushy shifts that slip everywhere, points to a pressure control solenoid stuck low, a worn pump or low fluid. A line pressure test separates them in a few minutes. Replacing the pressure control solenoid on a clean unit often brings the shifts right back.
If the valve body bores are worn or the separator plate is leaking, a replacement is the cleaner fix. We stock a remanufactured 4T45E valve body for 2007-up and a 4T40E valve body for earlier applications. Match the casting number on your existing valve body before ordering.
Problem 3: Converter Shudder
A light shudder at 40 to 55 mph under gentle throttle, like a rough road that is not there, is torque converter clutch shudder. Tap the brake while it happens. If it stops instantly when the converter unlocks, that is your answer. On a Cobalt it is often just degraded fluid that has lost its friction modifiers, and a fluid and filter change with Dexron VI clears mild cases. If it returns quickly, the converter clutch lining is worn.
Problem 4: No Reverse or Slipping Into Third
Hard-part failures on the 4T45E tend to show up as a loss of reverse while the forward gears still work, or a slip and flare on the 2-3 shift. The reverse clutch pack and the 2-4 band circuit are the usual suspects. Drop the pan. Red-brown friction dust and a burnt smell mean the clutches are done and it is a rebuild. Our 4T40E overhaul kit covers the soft parts for the family.
The root cause of most of these failures is heat. GM cooled the 4T45E through a small cooler in the radiator and called the fluid lifetime. Neither held up. If you are rebuilding one, flush or replace the cooler, and consider adding an auxiliary cooler.
Manual Transmissions
The five-speed manual behind the standard Ecotec is generally reliable, but high-mileage units can develop bearing whine and notchy shifts, especially when the fluid has never been changed. A whine that rises with road speed in every gear and goes quiet with the clutch in points at the transmission bearings. The SS models use a Getrag five-speed that holds up well when it is not abused, though hard launches on the turbo cars wear synchros and the clutch quickly. Always check the fluid level and type first; the wrong fluid causes hard shifting on these.
Fluid and Service
The 4T45E uses Dexron VI. Change it with the filter every 40,000 to 50,000 miles and it will outlive most Cobalts. We carry ACDelco Dexron VI by the gallon and a 4T40E/4T45E filter and pan gasket kit. Check the level with the engine running at operating temperature, following the procedure for your model year.
Is a Cobalt Worth Fixing?
Often, yes, if the problem is electrical. A solenoid kit, sensor or valve body costs a fraction of what the car is worth. A full rebuild is a closer call on a Cobalt with high miles and body or engine problems. In that case a quality used or remanufactured transmission may make more sense. Get the codes read and the fluid checked before deciding, because a lot of "the transmission is gone" Cobalts are a $150 sensor.
Repair Costs
| Repair | Typical Cost |
|---|---|
| Fluid and filter service | $150 - $260 |
| Speed sensor | $120 - $280 installed |
| Pressure control or shift solenoids | $300 - $650 installed |
| Valve body replacement | $650 - $1,100 installed |
| Torque converter | $900 - $1,500 |
| 4T45E rebuild | $1,800 - $2,700 |
| Used or reman transmission installed | $1,500 - $3,000 |
Bottom line: a Cobalt stuck in third is a code-reading job before it is a transmission job.
Chevy Cobalt Transmission Parts
4T45E solenoid kits, valve bodies, overhaul kits, filters and Dexron VI for the Cobalt. CoreTransmissionParts.com carries additional 4T40E and 4T45E parts.
4T45E Solenoid Kit → 4T45E Valve Body → 4T45E Filter Kit → Dexron VI Gallon → CoreTransmissionParts.com →FAQ
What transmission is in a Chevy Cobalt?
Automatic Cobalts use the 4T45E four-speed. Manual cars use a five-speed, and the SS models use a Getrag five-speed.
Why is my Cobalt stuck in third gear?
That is the 4T45E failsafe mode. A speed sensor, shift solenoid or wiring fault is the usual cause. Read the codes before assuming the transmission is bad.
Why does my Cobalt shift so hard?
A failed pressure control solenoid that defaults line pressure to maximum is the classic cause, often with a P0748 or P1811 code.
What fluid does a Cobalt automatic use?
Dexron VI. Change it with the filter every 40,000 to 50,000 miles.