In recent weeks you may have heard about Furches Performance‘s boosted LS4-swapped Monte Carlo, that has taken the internet by storm. It’s cranking out well over 700hp to the tires, and is gearing up to hit the drag strip for 2019. However, a lot of people want to know how you can make the 4T65E last for any real length of time, behind said engine.
Truth is, there’s little that you can do. The 4T65E can certainly be modified to withstand higher horsepower and torque levels, as well as the abuse you would expect from your average gear head, but it certainly has its limitations. In fact, the 4T65E is so woefully ill-equipped to handle the torque of an LS4, that these transmission tend to go south, even in a bone stock LS4 car at around the 100,000-mile mark. We’ve been there, done that.
Surely Brandon Furches has too, and that’s why he looks elsewhere for a gearbox to fulfill his Monte Carlo’s duties. Namely, the 4T80E.
Being the transmission that sat behind the Northstar-equipped Cadillac Eldorado, Seville, Deville, DTS and Oldsmobile Aurora, they’re fairly abundant. You could also find them in Bonneville GXP and V8 Buick Lucerne, since they’re also Northstar powered. Throughout their run, they were available with three different gear sets, depending on the make/model of the vehicle, as well as the model year; 3.11, 3.48, 3.71.
However, also based on configurations and some small details, Brandon Furches prefers the pre-’99 examples. In the above video, he also points out the pros and cons in utilizing a 4T80E in an LS4 build, as well as some niggles that you’ll just have to live with.
Rick Seitz is the owner and founder of GMEFI Magazine, and has a true love and passion for all vehicles. When he isn’t tuning, testing, or competing with the brand’s current crop of project vehicles, he’s busy tinkering and planning the next modifications for his own cars.
