4T65E-HD MN7 Transmissions and Torque Converters
Two major components of the car reside along the drivetrain between your engine and your wheels -- the transmission and the torque converter. LS4s come from the factory mated with 4T65E-HD MN7 transmissions; they're automatic transmissions that have 4 forward gears, are transverse mounted, come rated to 6,500 lbs, and are electronically controlled.
The 'HD' stands for Heavy Duty. Otherwise, they're based on GM's 4T65E transmissions, but with some beefing up of various components. MN7s come from the factory with upgraded input and final drive sun gears, carrier assemblies, and upgraded drive sprocket thrust washers. Additionally, MN7 have modified cases for relocated starter mounts.
4T65E-HD MN7s are rated from the factory at 280 ft-lbs of torque on the engine side, 400 ft-lbs of torque on the gearbox side. However, LS4s come from the factory rated at 325 ft-lbs of torque at the crank. Some have speculated that this may lead to long-term sustainability issues for stock transmissions. Unfortunately, there are hundreds of cases of transmission demise. My stock transmission -- even with life-prolonging upgrades -- broke down after 45,000 miles.
| Final Drive | 2.92:1 or 3.29:1 |
| 1st gear | 2.92:1 |
| 2nd gear | 1.56:1 |
| 3rd gear | 1.00:1 |
| 4th gear | 0.7:1 |
| Reverse | 2.38:1 |
Fortunately, Triple Edge Performance (TEP) has both stock and upgraded transmissions and torque converters available for sale. Their stock transmissions have been thoroughly inspected and comes with new seals, gaskets, o-rings, Teflon sealing rings, Borg Warner clutch plates, thrust washers, stator support bearings, input sun gear, valve body solenoids, and a transmission filter that's made in the USA.
Their high-performance street / strip transmission comes with the standard upgrades, plus new 4th clutch input shaft, friction plates / backings, drive chain, and more. You can also upgrade the input shaft, drive chain, and a custom clutch pack.
In addition to their transmissions, you can purchase replacement transmission coolers. Triple Edge Performance has several basic coolers available on the web site, but they also have another unit that's not listed -- a Tru Cool Max 4920 transmission cooler kit that comes with all of necessary hoses with AN fittings. This cooler can be top-mounted for use with a front-mounted intercooler should you ever decide to go forced-induction.
Also, Triple Edge Performance has a range of torque converters available ranging from stock replacement up to a custom, high performance torque converter with custom stall converter and custom billet cover that will bolt to stock LS4 flexplates without modification. The high performance torque converters are rated to over 1,000 horsepower and come with a full 5 year warranty. They can even customize the stall speed at no charge any time within the warranty period; all they ask for is the shipping cost.
I realize that I sound like I'm out to talk up Triple Edge Performance. I'm excited about their product because it's absolutely immaculately prepared, because I've heard from hundreds of individuals who have gone with TEP and are absolutely thrilled with the purchase. During my conversations with Dave Norris, the owner of Triple Edge Performance, I came to quickly come to understand that he knows these transmissions inside and out. Moreover, in addition to the time, quality, and attention to detail Dave puts into these transmissions, he's also a great guy and an honest businessman.
That said, be prepared -- word has gotten out about the quality of Dave and Triple Edge Performance's work and he's now very, very busy. As a result, it may take some time between when you place your order and when the parts arrive. Don't worry -- you'll get your parts.
After my stock transmission died, I went with the fully-built performance transmission, the high performance torque converter, and the transmission cooler kit. Triple Edge Performance crated and shipped the transmission via freight to a local transmission shop. The local shop took a few days to install the new parts and then shipped the old transmission back to TEP. When I originally purchased the parts, I also paid two-way freight plus a core charge.
I've got to say.. I absolutely love this transmission. Dave dialed it right in to exactly what I wanted. The 1-2 shift is much less than 1 second now -- it feels more like going over a seam in the road than a change in gears. It takes about as long for me to say 'pop pop' quickly as it does to change gears. It's crazy -- the car just doesn't stop accelerating.
The last thing I'm going to say on the topic is this -- even with a stock engine, there are hundreds of examples of 4T65E-HD MN7 transmission failing. Add performance parts (exhaust systems, headers, etc.) and one could guess about what will happen to the life expectancy of the transmission. However, with Triple Edge Performance's built-up drivetrain components, there are many who regularly race their LS4s after having thrown turbochargers, high performance cams and valvetrain components, nitrous oxide, and more at these transmissions.. and they're doing just fine!
.jpg/1200px-Ypsilanti_Automotive_Heritage_Museum_May_2015_060_(1979-2001_Hydra-Matic_3T40_transmission).jpg "4t65e Transmission")