Runge_Kutta

1000 Nm = 737 lbf/ft


General Motors Rear Wheel Drive Eight Speed Automatic Transmission
Technical Paper
2014-04-01
James Michael Hart, Tejinder Singh, William Goodrich

General Motors Rear Wheel Drive Eight Speed Automatic Transmission General Motors shall introduce a new rear wheel drive eight speed automatic transmission, known as the 8L90, in the 2015 Chevrolet Corvette. The rated turbine torque capacity is 1000 Nm. This transmission replaces the venerable 6L80 six speed automatic transmission. The objectives behind creation of this transmission are improved fuel economy, performance, and NVH. Packaging in the existing vehicle architecture and high mileage dependability are the givens. The architecture is required to offer low cost for a rear drive eight speed transmission while meeting the givens and objectives. An eight speed powerflow, invented by General Motors, was selected. This powerflow yields a 7.0 overall ratio spread, enabling improved launch capability because of a deeper first gear ratio and better fuel economy due to lower top gear N/V capability, relative to the 6L80. The eight speed ratios are generated using four simple planetary gearsets, two brake clutches and three rotating clutches. The resultant on-axis transmission architecture utilizes a squashed torque converter, an off-axis pump and four close coupled gearsets. The three rotating clutches have been located forward of the gearsets to minimize the length of oil feeds which provides for enhanced shift response and simplicity of turbine shaft manufacturing. The transmission architecture features a case with integral bell housing for enhanced powertrain stiffness. A unique pump drive design allows for off-axis packaging very low in the transmission. The pump is a binary vane type which effectively allows for two pumps in the packaging size of one. This design and packaging strategy not only enables low parasitic losses and optimum priming capability but also provides for ideal oil routing to the controls system, with the pump located in the valve body itself. The transmission controller is externally mounted, enabling packaging and powertrain integration flexibilities. The controller makes use of three speed sensors which provide for enhanced shift response and accuracy. Utilization of aluminum and magnesium components throughout the transmission yields competitive mass. The dedicated compensator feed circuit, used in GM six speed designs, was supplanted by a lube-fed design in order to simplify oil routing and enhance shift response. Packaging is within that of the GM 6L80 design, allowing for ease of application integration. The overall result is a robust, compact, and cost effective transmission which offers significant fuel economy and performance benefit, over its six speed counterpart, and shall provide an attractive balance of overall metrics in the automatic transmission market.

BeaZt

Is the date of that article correct April 1st?

Runge_Kutta

http://papers.sae.org/2014-01-1721/

themonk

Marty, we got to get you back, to the future......published in 2014 huh.

kozmic

While the date above does seem suspect, here is an article back from 7-12-2012 that also talks about a new 8-speed auto from GM being ready for full production sometime in the first quarter of 2014: http://www.13abc.com/story/18769971/...d-transmission

rcallen484

Not sure how the date is interpreted but that link is definitely legit.

http://papers.sae.org/2014-01-1721/

millpond

Nice find! Will wait for model year 2015 since I will be going with the auto.

This is the abstract. The article has not been published yet.
To be published 4/1/2014 and presented at SAE congress 4/8/2014. The specs for this unit means it could also be used for the C7 Z06!

BeaZt

True. The date sent me for a loop.

SpryGeezer

http://www.sae.org/congress/attend/program/
.

musclecar6

Well well well. Very interesting paper. If accurate, and it seems to address exactly the modern auto/DCT issues many of us have been talking about, we could be on the verge of deja vu all over again. Back to the future with a 2014/2015 repeat of the 2005/2006 C6 auto tranny transition. Suurprise, Suurprise !!!!

peter pan

Awesome looking forward to the new A8 tranny

JerriVette

Cool!

Shrike6

It will be interesting how Tadge tap dances around his previous statements about how an 8 speed auto was not needed.

runutzzzzz

It's not "needed" LOL

My next C7 will be a automatic!

DocHolliday

I switched to an automatic with this car and love it…I wouldn't go back to a manual in a million years.

ByByBMW

IF true, and I don't understand half of what that article said, then my decision to wait before buying the C7 will have been justified. I will wait for that transmission.

Shaka

Will we hear from the DCT loons?

MikeyTX

....... Oh really ?

MikeyTX

Oh I'm sure ......... Once they wake up......

W88fixer

I had thought about waiting till 2015 but the “bug” got me and I went ahead and do have the auto coming. I suspect succeeding years of Vettes will get better so I could use new features as an excuse to wait and wait and don’t want to. I guess I could rationalize and say I’m getting a proven transmission rather than a new product.

Not being catty here, I hope the new transmission is perfect out of the gate. I’m sure I’ll really enjoy what I’m getting. Don