ChocoTaco369

The thing that bothers me about the 6L90...well...here are the specs:



2007 Hydra-Matic 6L90 Transmission ( MYD ) 71706
Type: six speed RWD / AWD, electronically controlled automatic overdrive transmission with torque converter clutch. Clutch-to-clutch architecture, with integral Electro / Hydraulic Controls Module
Maximum engine power: 452 bhp ( 337 kW ), Diesel: 300bhp ( 223kW )
Maximum engine torque: 531 lb-ft ( 720 Nm ), Diesel: 520 lb-ft ( 705 Nm )
Maximum gearbox torque: 885 lb-ft ( 1200 Nm )
Gear ratios: MYD
First: 4.03
Second: 2.36
Third: 1.53
Fourth: 1.15
Fifth: 0.85
Sixth: 0.67
Reverse: -3.06
Maximum shift speed 6000 rpm
Maximum Validated Weights: ( Target ) GVW: 15000 lb ( 6803 kg ), GCVW: 21000 lb ( 9525 kg )
7-position quadrant: P, R, N, D, X, X, X ( X = available calibratable range position )
Case description: 3-piece ( Bell, main, extension )
Case material: die cast aluminum
Shift pattern: (2) Three-way on/off solenoids
Shift quality: Five variable bleed solenoid
Torque converter clutch: Variable Bleed Solenoid ECCC
Converter size: 300mm ( reference )
Fluid type: DEXRON© VI
Fluid capacity: w/ 300mm converter 300mm: 13.0L ( 10.8kg )
Transmission weight: w/ 300mm converter Wet: 109kg ( 240lb ) estimated
Pressure taps available: line pressure
Assembly Site: GMPT Ypsilanti, MI
Applications: Chevrolet Suburban
GMC Yukon XL
Chevrolet Silverado HD
GMC Sierra HD
Available Control Features: Multiple Shift Patterns ( Selectable or Adaptive )
Driver Shift Control ( Tap Up / Tap Down )
Enhanced Performance Algorithm Shifting ( PAS II )
Next Generation Tow / Haul Mode
Engine Torque Management On All Shifts
Altitude and Temperature Compensation
Adaptive Shift Time
Neutral Idle
Reverse Lockout
Automatic Grade Braking
Additional Features: Oil Life Monitor
OBDII / EOBD
Integral Electro/Hydraulic Controls Module ( Tehcm )
Control Interface Protocol - GMLAN



My problem is that this transmission is only rated to 452 horsepower and 531 ft-lb of torque. How is it going to hold 550 bhp/550 tq? Much less SUPERCHARGED 550 bhp/550 tq. That out-of-nowhere torque spike isn't exactly easy on the hard parts. How is this tranny going to hold 100 horsepower more than it's rated?

eliotmansfield

Perhaps by using torque management? - i.e. retarding ignition during shifts.

ChocoTaco369

That would have to be some SERIOUS timing retardation. They'd have to cut 100 horsepower to be at the MAXIMUM the transmission can hold! Even then it's dangerous for the tranny if you're putting it to its maximum every time it shifts.

Either this transmission is SEVERELY underrated, they're going to beef it up even more, the article's claims of the new Caddy's power is BS or it simply won't be offered in an automatic.

I don't think GM would offer a Cadillac with that extreme of power level and then ruin the driving experience that badly with that heavy of torque management. The torque management would have to be absolutely obscene, and even so, when climbing through the RPM's it'll still be 100 horsepower over max. Something's seriously wrong here.

Besides, I'm sure GM is totally aware that people are going to go out and get an untraceable tune where timing is advanced and torque management is deleted anyway. Since the tunes are undetectable, GM would be replacing hundreds of trannys because of this. I think they'd want to make the tranny be able to hold more than it's getting stock to prevent this.

Ragtop 99

iTrader: (7)

The tune might be untraceable, but flashing back to stock is. How many miles are you going to drive with a busted tranny after you reflash a stock tune back into the car? Opertaing hours and miles since last flash is logged. Are you going to pull all the engine mods too before it goes to the dealer? Sure it happens, but it is a small percentage of the time.

6L80 is holding up to a bit more power than it is rated for, so maybe 500 - 550 rwhp will be ok for 6L90.

The 880 ft-lbs actually provides some hope. Keep the stall speed & STR reasonable and you'll stay below that.

Gilbert@Ace Racing

I have some calculations to make... But I'll try to get to that this weekend. I think it would be interesting to determine the launch ratios for this unit with several different gears sets and tire combinations... then compare them to the most popluar units.

g

Ragtop 99

iTrader: (7)

I did some calculations for a guy on corvette forum, comparing the C6 A6 with 2.73s and 3.15s to the ratios being used in the Z51 M6 and a couple other combos. If you want that stuff, PM me.

Circle-D

iTrader: (21)

I have done a few custom converters for the C6 A6 guys and that first gear really affects the stall. I used a 258mm, the stock was 300mm, and the car barley stalled over 2000 rpm. It was a bit of work, it has a new bolt pattern, different OAH, different input splines, different stator splines and a different hub. I would be happy to do some experimenting with the converter and a high HP application if somebody can get the computer figured out.

Gilbert@Ace Racing

Is that a representative "explodogram" of the converter in question?

g

Circle-D

iTrader: (21)

it is my photoshop work of the 258mm converter i built for the 6l80/90E

Circle-D

iTrader: (21)

A few more shots if interested.





I also did a multi disk version, but I forgot to take pics.

Gilbert@Ace Racing

Thanks... the reason I asked was that I did not recognize the piston as one I am familiar with. It looks like it is a well built piece that can take some punishment.

g

Circle-D

iTrader: (21)

No, thank you, it is a billet piece I make. I leave the ribs there for strength, it takes a little longer on the mill but worth it. The whole piston only weighs 4lbs.

on a side note, still getting some pieces for the 4L80E, should have a prototype in a month or 2.

Blk02Ls1A4

iTrader: (3)

I would like one of these in my car.

I was considering an M6 swap, but ever since this tranny came out I have been hoping for one of these. When will one of you all be offering a swap kit?

newby

uhh... same rating as a 4l80E. the reason the 4l80 and this trans can handle the higher power in a car is because of the GVW. the trans can handle 531 ft-lb behind a 15,000 lb vehicle. scale that back to a 2-3k lbs car and you get a lot higher ceiling.

the new 6l90 is sure to have some teething problems as did the 4l80 and the 4l65 we all love so much, but I believe the aftermarket will take care of any short comings that arise. (ie higher performance clutch materials, external controllers etc)

as far as the gearing, go to fatboyracings website and check out their transmission/gear ratio/tire comparison tool and throw some of your favorite combinations at it.... you will see that the any 6 speed trans is worlds better then any 4 speed trans as far as the splits. the 1-2 split is not ideal on the the 6l90, but its pretty damn good and makes the 4L60 trans look as dated as a th-350 does today.