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.

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

jdmvette

3 Z06ZR1

Yep ! This is a game changer!

keagan

Gotta give it to GM, they don't hold back when it comes to innovation with the vette. This thing is turning out to be crazy. Thanks for the info.

JoesC5

And the Silverado, Camaro, and rear wheel drive Cadillac's. That new transmission was not designed strictly for the Corvette and most of them will be used in pickup trucks.

keagan

Agreed, I would of said the same thing on the their respective sites. Lately they are doing some great things, I'm glad the vette is getting some love

Shurshot

Rowing gears is fun but second place is only the first looser. I am looking forward to see what GM has accomplished with this new tranny

Anyway:

When I stopped by to see a new Impala SS (bummer) the salesman wanted me to come back when they get a new performance based Colorado 6.2 that may get the LT4.

skank

You didn't believe him, did you???

Wulverine

Nothing innovating about an 8 speed transmission.

Racer X

So you think the only innovative about an automatic transmission is the number of gears? You have a very narrow view of the what innovation is. There was a lot more in that release than the number of gears.

This may mean that the Z06 will have an available automatic transmission.

They point out a number of innovations, however, the proof will be in the results.

HolyRoller

It looks very encouraging and authentic, and it would sure boost Z06 sales, but did anybody notice the date on this paper--April 1?

04_Z06_CE

This is great news from the slushy 6 speed disappointment in the c7. The Z will be a strong runne

LT1V8

Can someone explain why this is innovative or exciting? A Z06 with an 8 speed slush box doesn't excite me at all.

Jp23rockstar

You knock it, but you haven't even the Z06 perform.

musclecar6

If they get this 8 spd auto right and put it in the Z06, which they absolutely should if it is technically feasible, my guess is they will sell a lot more auto Z06's than manuals, just like the base/Z51 C6's, C7's etc. For those who have never tried a modern 8 spd auto or DCT, you can try them both out at the BMW dealer. When I replaced my 06 C6/A6 coupe last year with a new 2012 CTS-V A6, I first tried out a BMW M3 & 135 Is, both with DCT and a 3 series with the latest 8 spd auto. The DCT's both had instant right now shifting, both up or down with seamless rev matching. The 8 spd auto, though not quite as quick as the DCT's, was still very close and seamless( probably 93/95 percent as fast). Both were in a different league than the A6 that I got in my CTS-V ( my 06 C6/A6, being the first year of that tranny, was a total POS except for Caddy cruising with terrible lag and "lurching" manual paddle downshifts. Had it tuned by two well known tuners, & it still was no good cause the hardware was their lousy first effort).

I ultimately decided on the CTS-V over a new M3, cause there had been HUGE improvements over the A6 in my 06 C6. That said, although the C7 A6 is now in what looks like it's last year and is the best yet, the 8 spd should be a nice step up, maybe even rivaling the DCT/PDK's of BMW/Porsche for instant right now fun for all us vette junkies.

LFZ

Where does it say that this trans will be offered in the new Z06?

musclecar6

Nowhere yet. Just people hoping ( or not) at this point.

JMB

Hmmmm.....with a torque rating of 738 ft lbs sounds like it "could" be offered in a Z06!

QUIKAG

It will definitely be available in the Gen 3 CTS-V which will very likely have a version of the LT4. So, it is HIGHLY likely this will be a transmission option in the LT4 Z06.

One of the reasons, the C6 Z06 didn't come with an automatic is GM never validated an automatic transmission to the LS7. The 6L90 could have easily handled the torque, but the LS7 spun almost 1,000rpm higher than the LSA. So, not sure if that was the main issue. Probably that and the relatively low demand for an auto C6 ZO6.

millpond

What you are reading above is the abstract of a paper that will be published on 4/1/2014 and presented to the SAE on 4/8/2014.