Open up any magazine or cruise the information super-highway and odds are the main topic of conversation is horsepower-and loads of it. We have it all these days with massive stroker engines; a plethora of cylinder heads and intakes; and, of course, an over-pouring serving of nitrous, blowers, and turbochargers. But if there is one thing that most of us learned quickly in the game of power, it's that there needs to be something behind it to harness that power. A weak link inside the transmission tunnel will lead to big frowns and frustration, as you can't have fun with the goods under the hood.
If an automatic transmission is part of your assault then you have a few options-the 4L60E transmission was introduced to many rear-wheel-drive GM models back in 1993, replacing the 700-R4 overdrive transmission. Without getting too into it, the 700-R4 is hardly a performance-oriented transmission nor one that could withstand the abuse of a severe increase in power. The 4L60E, while a welcome change, does have its limits. "The PerformaBuilt 4L60E holds up to about 750-800 rwhp very reliably," commented Alan Pickering of PerformaBuilt. After that, enthusiasts have to look elsewhere and that is where the path to quick times has several turns and forks in the road.
There is the usual option of going with a non-overdrive transmission, either a TH400 or Powerglide will hold up to anything you can throw at it. But we live in an age when we want everything without any comprises, it doesn't matter if it's with our cell phones or our cars. That said-who doesn't want to have an overdrive automatic transmission to back a newly twin-turbocharged 427ci engine that makes in excess of 900 rwhp? The 4L60E is not up to snuff for that tour of duty. Its internal design is not capable of handling more power no matter what parts are used, replaced, or bulletproofed. A nice option is to turn to the 4L80E transmission, a cousin to the 4L60E, that was used in several GM trucks. Interestingly, the 4L80E also showed up in several models under the Bentley, Rolls Royce, Jaguar, and Aston Martin brands.
GM designed the 4L80E to be a beefy and strong transmission to withstand the rigors of towing, heavy loads, and big power under the hood. Truth be told, the transmission is nothing more than a TH400 with an Overdrive gear and electronic control. The gearing shows First gear as 2.48:1, Second 1.48:1, and 1:1 ratio for Third. Overdrive is a high-speed friendly 0.75:1. The transmission is capable of backing some of the wildest combinations when it's properly prepared. "The PerformaBuilt 4L80E can handle 1,000 rwhp with ease. We have one customer in Texas with a twin-turbo Corvette that makes 1,400 rwhp without any trans troubles," stated Pickering.
To get the 4L80E up to snuff, PerformaBuilt does extensive modifications internally. The company is so confident in its upgrades that it dares customers to break the transmission. A standard one-year warranty is included and that is bumped up to two years if combined with a PerformaBuilt torque converter. According to Pickering, the company dissects the transmission front-to-back and modifies everything. "It's a balanced unit and you have to maintain that balance," was Pickering's comment about the modifications. Each mod inside the transmission affects something. Increasing pressure and tightening clearances will have an effect on other components. PerformaBuilt maintains the equilibrium to prevent failures.