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Thread: 4t45e -> 4t65e swap

  1. #1
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    4t45e -> 4t65e swap

    I am using the drive train from a 2006 Cobalt SS (2.4 NA) in a custom vehicle. I am worried that the 4t45e may not hold up and gearing options for the 4t65e are more in my favor anyway. Mating the trans to the engine is not an issue for me but my question is about the TCM's. From a control standpoint the two transmissions are similar with mostly the same inputs and outputs so it stands to reason that the Cobalt TCM may be able to control the 4t65e. But if it would be better to use the 4t65e TCM instead that would be fine too. But then how do I make the 4t65e TCM play nice with the Cobalt ECM?

    I know that pressure is controlled via PWM as well as some other stuff being controlled by the TCM. But I will be shifting the trans full manual 100% of the time. That being the case is there a way to eliminate the TCM altogether?

  2. #2
    Advanced Tuner Dr. Nopps's Avatar
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    Sorry to reply without a direct answer to your question but... I've found the 45's from my Cavalier & Malibu to be holding up to some pretty hard demands. All the while droves of police cars keep coming into my local dealership with blown, cooked, and even shattered 4T65E tranny's!?? My mad scientist/GM master tech friend and I are stumped on this one, seeing as the 65's come in the next body class up with larger engines as well. Funny as you would naturally think anyway: "65 has gotta be better than 45". But if you really want, the swap should work out for you if the inputs from the PCM are the same/all there. As long as the TCM doesn't need to see a VIN# matched to it from the original PCM or anything. (You would obviously need to transfer all the relevant values from the Trans & Speedo section of the tune over as well, with special regards to Final Drive Sprocket Ratio.) Seeing as this is for a custom (vehicle/race car?) I personally would source a cheap 4T45E, or even a manual tranny from an old Cavalier. If you're still leaning towards the automatic route, then use the rebuild kit from a 4T45E that came in a much heavier more powerful vehicle to beef it up. You would then have a tough 4T45E with an insane final ratio. (125-130MPH top speed in overdrive if you're really pushing the RPM's) Not much for MPG's but you could REALLY pull through those gears pretty quick!
    Last edited by Dr. Nopps; 08-18-2014 at 04:43 AM.