The story of the General Motors 4T45E began with the Turbo-Hydramatic 125. It was the first of the line of GM automatic transmissions that culminated in the production of the 4T45E. Production of the hydraulically controlled predecessor of the 4T45E was launched in 1980 and continued through 2001 — an impressively long run for any transmission design. It was a fresh design that incorporated some components from both the Turbo-Hydramatic 200 and the 350.

Eventually, the 125 was renamed the 3T40 in keeping with the company’s newly adopted naming convention. In 1995, the electronically controlled 4-speed 4T40E was rolled out and the gradual phase-out of the 3-speed 3T40 ensued. Ultimately, the 4T40E developed into the current 4T45E, 4T65E, and 4T80E line of GM automatic transmissions.

General Motors began building the 4T40E transmission in 1995 and continued producing that version through 2010. However, in 2005 the automaker began installing the 4T45E. So, check your VIN and confirm which transmission you have, before you obtain a replacement. 

Because the GM 4T40E and 4T45E are produced only with electronically controlled torque converter clutches and there are no hydraulic versions, you will find them typically referenced without the “E,” as simply 4T40 and 4T45. Also, be aware of additional alternative names for versions along this line of transmissions, per internal GM naming codes.

Specifically, you may find that the factory product ID codes are used instead of codes 4T40 and 4T45. To help clarify what you’re seeing in the varying identification codes you are likely to find being used on GM transmissions, a Regular Production Option (RPO) is indicated by a 3-digit code label used in assembly plants and dealerships. The production labeling for the 4T40 transmission is MN4 and for the 4T45, it’s MN5. So, if you see the MN4 designation code, that means you have a 4T40, and the MN5 code indicates that the transmission is a 4T45.

As explained, the 4T45 is an upgraded version of the 4T40. The 4T40 was built for 1.5 L to 3.0 L engines and has a more limited capacity to handle vehicle weights of up to 4,000 lbs. with engines generating up to 190 ft-lb of torque. It was also, however, paired with 4-cylinder models from GM’s Ecotec line.

The 4T45 transmission can function ideally in vehicles weighing up to 4,500 lbs. Its strength is attributable to the utilization of multiple sprocket combinations as well as two differentials. The 4T45 is for installation in vehicles with 3.0 L to 3.5 L engines that generate as much as 205 ft-lb of torque. 

Two distinctly different bell housing designs were used for the 4T45E transmission. One is for installation with V6 engines (the Metric Pattern). The other uses GM 4-cylinder Ecotec models (Ecotec Pattern).

Predecessors of the 4T45E (also called the 4T45 and the MN5) include the 4T40E (also called the 4T40 or MN4). Successors of the 4T45E include the 6T30, 6T35, 6T40, 6T45, 6T50, 6T70, 6T75. Note that the “E” designation has been phased out and is not much associated with these later designs. That’s because hydraulically controlled torque converter clutches in the GM line, as with other modern transmission manufacturers, have gradually become a bygone system feature.

Cars with the 4T45E Transmission

The 4T45E transmission came in the Chevrolet Cavalier, Chevrolet Cobalt, Chevrolet Corsica, Chevrolet Malibu, Chevrolet HHR, Chevrolet HHR SS, Oldsmobile Alero, Oldsmobile Cutlass, Pontiac Sunfire, Pontiac Pursuit, Pontiac Grand Am, Pontiac Grand Prix, Pontiac G6, Saturn Ion, Saturn Vue, and Saturn L-Series. Check to ensure that the 4T45E transmission was the unit installed in your model of the vehicle during the specific model year in which your car was manufactured.