What Goes Into Building A 1,000HP-Capable 6R80 Transmission

Ford’s 6R80 six-speed automatic transmission is the go-to transmission for Coyote-swapped vehicles, and ATI Performance Products is offering upgraded versions capable of handling up to 1,000 horsepower. The company realized that the transmission could be used in applications other than the Blue Oval, and engineered a solution that allows for the transmission to be mounted behind your favorite small-block Chevy, LS, or LT engine. Whether you have a street rod in need of a better overdrive transmission or a 1,000-horsepower street car that you’re racing on the weekends, ATI, along with Raybestos and US Shift, have 6R80 transmission options for a range of power levels.

After a suitable 6R80 case core is procured, the ATI staff checks the case for issues. “Inside, there are places where some of the parts bang on the lugs of the case, so we check to make sure there are no cracks and no threads pulled out,” Beattie tells us. Once it gets approved, the case is cleaned and then for this build, it is CNC machined to accept the custom Chevy bellhousing

A Need for 6 Speeds

Modern overdrive transmissions do a great job at reducing engine RPM for comfortable cruising and better fuel mileage. As ATI Performance Product’s J.C. Beattie explains, the 6R80 is a much better option over previous four-speed automatic transmissions.

“The AODE and 4R70W Ford trans are pretty old technology. They do work and they are fine, but they won’t hold the power that a 6R[80] will, you have a much wider gear split and they do not shift as quickly. The 6R is a superior transmission for drivability with dual overdrives and much more current engineering. There are also four-speed transmissions that get a six-speed conversion with some changes internally, but having a real six-speed is a much better option and for the same price, makes it an easy choice.”

No matter the level of build, many factory 6R80 internal components are used. “We look at the shafts to make sure they are not worn out, we look at the bushings and make sure the drums are not cracked,” Beattie explains. “Sometimes we find worn-out shafts from bushings going bad, and occasionally a solenoid gets stuck when the clutches are going away and sometimes it’ll crack a drum. A lot of components are available to replace with factory replacement parts.” Once all of the parts are ready, assembly can begin, and that starts with measuring the clutches and plates

“If it fits in there, it will fit in a lot of stuff,” Beattie says.

Appropriately upgraded, the 6R80 is capable of handling 1,000 horsepower in a, 3,300 to 3,400lb car, according to Beattie.

“If it’s a true drag car, you don’t need a six-speed, you need a three-speed. For those who have a fun hot rod or play car and still want to jump on the freeway and cruise in overdrive, that’s another story.”

Raybestos provides a clearance range for the stack of components between clutch and pressure plate. They can’t be too tight or too loose otherwise they will not function as intended, so each component and stack is measured and adjusted if needed to be within tolerance

Battle of the Sixes: 6R80 vs 6L80E

ATI Performance Products has been building GM transmissions for decades, but when it comes to six-speed transmissions, Ford’s 6R80 offers at least one major benefit that GM’s 6L80E does not, full control via an external computer box.

“They are almost identical from a factory standpoint,” says Beattie, of today’s six-,eight-, and ten-speed automatic transmissions. “They were all co-developed from ZF between GM and Ford, so it’s very much the same idea for function, capacity, and holding ability. With the GM 6.0-liter, you must have expensive tuning equipment and cannot control the transmission with a stand-alone TCU like the US Shift box. You can use a handheld programmer to raise or lower shift points, change tire size, etc., but can’t add a transbrake, torque cut, second-gear leave, shift process, or just adjust general functions of the trans to have it shift harder, softer, earlier, or later.”


The Chevy Connection

As previously mentioned, ATI has engineered a solution where they modify the 6R80 case to accept a Chevy bellhousing,  allowing it to work behind Gen-I small-block, LS, and LT Chevy engines. In order to accomplish this, ATI needed to adapt the 6R80 transmission case and bellhousing to the correct bolt pattern, build a custom torque converter, and needed a way to control the transmission independently.

“You can have a true standalone, fully controllable trans with the 6R80, but with the 6.0-liters, you cannot,” Beattie says. “The point of the package is to have a late-model six-speed overdrive and have full external control, which is where US Shift comes in with their box.”

This is ATI’s 300M-steel intermediate shaft, which is one of the hard-part upgrades ATI made for this build. This comes standard in the 700-horsepower and higher transmission builds. “If you think about the gear ratios, when you’re under a lot of throttle and shift, you lose a lot of mechanical advantage and it’s hard on the parts,” Beattie says. “There is added stress on the transmission and the intermediate shaft is the one that would take that stress.

The electronic control is easy, by comparison, to the physical and mechanical changes that needed to be engineered for the adaptation.

“We have a CNC program to machine the case. The Chevy bell locates on the pump and attaches through those 13 bolts,” Beattie said. “We build a hybrid torque converter with a Ford hub and a Chevy pilot, built to correct the spacing to mount it to a small-block, LS or LT.” The torque converter is available with or without lockup.

6R80 Fortification Plan

One of the attributes of the six-, eight-, and ten-speed transmissions is the torque cut feature, which cuts engine power during shifts, and uses the “shift in progress” function.

“The torque cut feature is the only thing that keeps these clutch-to-clutch transmissions alive,” Beattie explained. “They are all good and strong because of the torque cut. The ten-speed in our 2017 Camaro ZL1 is a hard trans to break because it has so much torque cut. The torque cut goes from 20 degrees to negative 20 of timing on the shift, and we played with it a good bit trying to hurt it.

Each clutch pack consists of a group of alternating clutches and steel plates. Fitting additional GPZ clutches and steels in each pack improves power-holding capacity.

The 6R80 is a decently beefy unit and with the new Raybestos clutch kit adding the clutches and steels, it adds a lot of extra capacity. Every area has 1 to 3 additional clutches, except for one. Raybestos has been around forever and they are at the top of their field for these types of parts.

The Raybestos components used in this build utilize the company’s GPZ material.

“The American-made, proprietary Raybestos Powertrain GPZ friction material used in the 6R80 Torqkits is engineered with an extremely high and stable friction coefficient to increase transmission durability, increase transmission torque capacity, and reduce core temperatures,” says Raybestos’ Nick Truncone. “The stability of GPZ’s friction coefficient allows the friction material to maintain optimum performance capabilities as both speed and power increase. That results in smooth and quiet shifts. The unique properties of GPZ material combined with increased clutch counts in each clutch pack deliver enhanced performance in 6R80 racing, street-strip, and towing applications.”

Each clutch pack must maintain a certain amount of clearance in the housing and the builder checks these during assembly. Doing this is even more critical when you are installing aftermarket components.

The Raybestos Torqkit used in this build (P/N: RCPTK-6R80) increased the clutch count by 10 friction plates to a total of 36, which adds about 40-percent more clutch surface to increase performance and durability.

Standalone control for the 6R80 transmission

Automatics such as the 6R80 are electronically controlled from the factory, and to use them in an aftermarket application like this, they require a standalone transmission control unit. Enter Baumann Electronic Controls and its US Shift Quick 6 Gen2 Clutch-to-Clutch Transmission Control System.

Here, the forward drum has been installed and the transmission is ready for the pump to be installed.

“The Quick 6 controller lets you use this transmission with any engine you can bolt it to and in any vehicle,” says Karl Baumann. “It can work with EFI or carburetors. It gets all of the signals from the transmission, the RPM, and the throttle position signal from the engine, and offers a torque reduction feature. In a 400-horsepower application, [torque reduction] doesn’t matter, but when you’re running 990 lb-ft of torque, then it matters — you don’t want to break stuff.”

The US Shift Quick 6 controller is a plug-and-play unit to allow the use of the transmission in any application it can bolt up to. ATI uses it during dyno testing.

The 6R80, 6L80, and ten-speeds are clutch-to-clutch transmissions and are completely different than controlling an older four-speed automatic. The valve body in these transmissions doesn’t have a lot of intelligence as the ECU or TCU is taking over a lot of functions in much greater detail and capability.

ATI recommends Mercon LV (or compatible) transmission fluid for the 6R80. Once the transmission build is completed, the unit is tested on a dyno to ensure proper operation.

“In the hot rod business, you don’t know anything about the weight, chassis, vehicle, so it has to be adaptable. The more you drive the Quick 6, the better it learns from every shift. It makes corrections on the fly and records them so next time the shift will be better,” Beattie says. 

Having this type of control provides for additional options that US Shift includes, such as a transbrake, torque cut, as well as a second-gear-leave function, and these are all easily accessible through the controller’s software. Best of all, the Quick 6 controller is plug-and-play with a wiring harness that connects the handheld controller directly to the transmission.

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Steve Baur

A lifelong automotive enthusiast, Steve Baur attended the University of South Florida for journalism and has worked as a technical editor and editor for numerous automotive publications for over 20 years.
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