One thing that has always steered me away from an automatic in the past when choosing transmissions has been the ability, or lack there of, of the automatic transmissions to effectively downshift on a road course. Most don't seem to rev-match. Can the 4L and 6L units do this well?

They all have multiple modes. From our real world experience, use that capability wisely. You have 100 modes under your right foot relative to TPS. Build a calibration that is mild at 0-30% TPS, then aggressive from 30%-100%. There is no logical reason to have a calibration that's soft at WOT (bad), or harsh at 10% TPS (also bad).
A/B modes are best reserved for applications like trucks that might have significantly varied weight (i.e. towing) or applications where traction conditions vary greatly such as snow or mud.

When road racing a 4L based trans (including the TCI 6X), run a bit more rear brake bias and instead of downshifting as you approach the corner, downshift at the apex to power out of the corner and rocket down the straights. Three pedal cars have steadily increasing rpm curves down the straight. Auto cars see a vertical spike, then a much more horizontal curve.

The 4L design is just not as good going into the corner, but better coming out. With the wrong converter and lock up calibration, acceleration will be sluggish, and the drivetrain will feel like it's in neutral every time you lift.

As for rev matching, the torque converter is a fluid coupling and therefore largely unnecessary with the 4L design. And no none of the available trans controllers ask for a blip from DBW throttle pedals. It would sound cool though.

Now the 6L has 3 pedal style engine braking AND torque multiplication under acceleration.

Sorry for geeking out.

Amituk,

I am currently running a 6L80e/Built LS3 set-up in my 67 Camaro. I am using a ProTorque converter, Twistmachine Paddles, and a Tranny tune from Zero Gravity Performance in Arizona. I originally intended to go with a T56, but an now very happy with my 6L80.

Here is my build thread on Pro-touring: (please excuse my initial reference/misprint to the tranny as a 6L90.....I have a 6L80)

http://www.pro-touring.com/showthrea...ro-Build/page2


Driveline specs:
Gear Ratio: 3.70
Rear tire size: 18" x 10" x 4.75" BS, 285/40 Tire (Toyo Proxies)
Car weight: 3200 #'s est.
Torque converter: 3000 stall, 10" Pro-Torque
The car has a fairly aggressive cam from COMP cams, along with headers and a tune. The car produces 420 HP at the tires.


Hope this helps!
Thanks,
Bobby

My personal opinion is that if I'm building a car with intentions of driving it on a road course there is no other option than manual.

I believe a 6x and 4l80 are both .75 overdrive ratio. As a comparison, 5th gear in a T56 is .74 and 6th is .50.

Think again, tuning it to perfection can be nightmare..

Have you seen this: http://www.mastershift.com/p_street_manual.html

Look at the vids , really cool!

Gosh, the first pic on that page looks awful familiar. They used to be good customers of ours, then copied our part almost exactly. Didn't even bother to change the design in the slightest. Beware.

You know what else Steve...I saw this in action @ SEMA. Sure seemed like a very slow shift to me. No idea if it was just the demo unit, but I was thinking I could shift manually in less than half the time.

Keep Geeking out! Your knowledge of the 4L and 6X are great. I like reading your in-depth post about the 4L. Keep it up.

Great thread!:popcorn2: