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Which Transmission Is in Your G6
| Engine | Transmission | Notes |
|---|---|---|
| 2.4L Ecotec | 4T45E four-speed | Most common G6 combination; some late cars got the 6T40 six-speed |
| 3.5L V6 | 4T45E four-speed | Base and GT sedans and coupes |
| 3.9L V6 | 4T65E four-speed | GT and convertible models |
| 3.6L V6 (GTP, GXP) | 6T70 six-speed | Highest-output G6 |
The fastest way to confirm is the service parts label in the trunk. Look for MN5 for the 4T45E. If your label shows a six-speed code, you have a 6T40 or 6T70, and the problems below for those units apply instead. Do not order parts on engine size alone. The 3.5 and 3.9 look similar from the outside and take completely different transmissions.
4T45E (2.4L and 3.5L): Stuck in Third and Hard Shifts
The 4T45E is the heavier version of the 4T40E and is the transmission in most G6s on the road. Its failures are mostly electrical and heat related, and that is good news, because electrical is cheap.
The classic complaint is a G6 that suddenly will not shift and pulls away from every stop in third gear with the check engine light on. That is failsafe. Speed sensor codes (P0715, P0720) and shift solenoid codes (P0751, P0756) are the usual triggers. Read them before you let anyone tell you the transmission is finished. The second classic is brutally hard shifts with a P0748 or P1811, which is the pressure control solenoid failing and line pressure going to maximum.
Once the pan is down on a high-mileage unit, replace the full solenoid set rather than chasing one at a time. Our 4T40E/4T45E solenoid kit covers the G6. If the shifts are good cold and bad hot, the valve body bores are likely worn, and a remanufactured 4T45E valve body is the cleaner repair for 2007-up cars. Match your casting number before ordering.
Hard-part failures, usually loss of reverse or a slipping 2-3 shift, mean the reverse clutch or 2-4 band has burned up. That is a rebuild. Our 4T40E/4T45E master rebuild kit has the frictions and soft parts.
4T65E (3.9L): Slipping, Flaring and Overheating
The 3.9 V6 cars use the 4T65E, a bigger four-speed with a different set of habits. The weak spots are the input and third clutch circuits, the pressure control solenoid, and a 1-2 accumulator area that develops leaks and soft shifts. A 4T65E that flares on the 2-3 shift, or slips going up a hill, has usually lost pressure somewhere in the input or third clutch circuit, and burnt fluid on the dipstick confirms the damage is done.
Early solenoid and pressure problems can be fixed with a 4T65E solenoid kit with harness or a 4T65E valve body for 2003-up. Once it slips, it needs a rebuild, and our 4T65E master rebuild kit is built for the 2003-up units in the G6.
6T70 (3.6L GTP and GXP): Lost Third, Fifth and Reverse
The six-speed GXP is the most fun G6 and the one with the most dangerous transmission habit. The early 6T70 is known for the 3-5-reverse wave plate breaking. When it fails, the car typically loses third, fifth and reverse at once, sometimes after a harsh shift or a clunk. Pieces of the broken wave plate end up in the fluid, so a pan inspection will show metal. That is a teardown, not a fluid change. We go deep on this in our 6T70 wave plate failure guide.
The 6T70 also suffers from valve body and TCM-related shift flares, especially on the 1-2 and 2-3 shifts. Before any hardware, make sure the TCM has the latest calibration and run a relearn. If the valve body is at fault, our 6T70/6T75 valve body covers it. For the rebuild itself, the 6T70 banner rebuild kit for 2009-2013 handles the frictions and steels, and the 6T70 overhaul kit covers the seals and gaskets.
6T40 (Late 2.4L): Harsh Engagement and Shift Bang
The few G6s that got the 6T40 six-speed share its well-known traits with the Malibu and Cruze: harsh 1-2 and 2-3 shifts, a delayed engagement into drive or reverse, and solenoid body faults. The 6T40 is sensitive to fluid level, so check it with the procedure through the check plug at operating temperature before chasing anything else. A 6T40 solenoid kit and a 6T40 filter and pan gasket kit cover the common service work.
Fluid and Service
Every automatic in the G6 takes Dexron VI. GM called it long-life, but in a car that is now 15 to 20 years old, change it with the filter every 40,000 to 50,000 miles and do not skip the filter on the four-speeds. We carry ACDelco Dexron VI by the gallon and the 4T40E/4T45E filter and pan gasket kit.
Repair Costs
| Repair | Typical Cost |
|---|---|
| Fluid and filter service | $150 - $280 |
| Speed sensor (4T45E) | $120 - $280 installed |
| Solenoid replacement | $300 - $700 installed |
| Valve body replacement | $650 - $1,300 installed |
| 4T45E or 4T65E rebuild | $1,800 - $3,000 |
| 6T70 wave plate rebuild | $2,500 - $3,800 |
| Used or reman transmission installed | $1,600 - $3,500 |
Bottom line: on a four-speed G6, start with the codes and the solenoids. On a GXP, any sudden loss of reverse and third means stop driving it and inspect the pan.
Pontiac G6 Transmission Parts
4T45E, 4T65E, 6T40 and 6T70 solenoids, valve bodies, rebuild kits, filters and Dexron VI for the G6. CoreTransmissionParts.com carries additional GM transmission parts.
4T45E Solenoid Kit → 4T65E Parts → 6T70 Parts → Dexron VI Gallon → CoreTransmissionParts.com →FAQ
What transmission is in a Pontiac G6?
Most use the 4T45E four-speed with the 2.4L or 3.5L. The 3.9L uses the 4T65E, the 3.6L GTP and GXP use the 6T70 six-speed, and some late 2.4L cars got the 6T40.
Why is my G6 stuck in third gear?
That is the 4T45E failsafe mode, usually triggered by a speed sensor, shift solenoid or wiring fault. Read the codes before assuming the transmission is bad.
Why did my G6 GXP lose reverse and third?
That combination points to a broken 3-5-reverse wave plate in the 6T70. It requires a teardown and rebuild.
What fluid does a Pontiac G6 automatic use?
Dexron VI in every G6 automatic. Change it with the filter every 40,000 to 50,000 miles.