JakeFusion

iTrader: (7)

Interesting thread...

I need to go do some testing. I have my trans tuning done where it's pretty acceptable for me, but I don't know what's better from say a 40mph roll when you have a built trans and a high stall converter.

The stall almost makes a downshift moot to be honest frum roll.

RevGTO

iTrader: (12)

Especially if your converter stalls at 4200 But with a cam peak torque will be higher than that.

I will add that I have roll raced by stomp-downshift. With the Transgo shift kit my downshifts are pretty close to instantaneous. A stock transmission with torque management and stock shift timing can be really slow.

justin hover

40mph in 2nd gear has me reving at 4k+ and sounds like ***** about to blow up!!! Last time I remember cruising at 40/45mph and downshifting into 2nd, seems like I just about slammed my face into the steering wheel, because of the stressful braking effect of the motor.
IDK...maybe I need to try this approach again.

Jake's Performance

iTrader: (2)

Another issue with the 4L60E's is that on a 4-3 downshift, the forward sprag is assumed to lock back up, but in many cases it doesn't. It skids and this causes an overspeed of the rev input drum and sun shell. Usually evident by the marks on the sprag inner race, and swollen drum/shell.
Doesn't matter who builds it, it's one of the inherent weaknesses of the design.
3-4 apply area and forward sprag have never been addressed in these units, and likely won't be due to available space.

redtan

iTrader: (5)

So would it make more sense to keep the car in 3 when driving spiritedly?

I like doing that you not have to worry about getting into OD 4th gear but I find it that a 3-2 or 3-1 downshift to be quicker and more violent than a 4-2 or 4-1. And if it avoids some of the downfalls of the transmission then even better.

RPM WS6

iTrader: (3)

I've seen it noted before by some trans builders that the concern here is line pressure drop on the WOT 2-3 shift when in 3rd, as the overrun clutch is engaged and seems to sap pressure. The obvious concern then would be 3-4 clutch wear.

I too have noticed a more "violent" (and consistent) downshift from 3-1 (vs. 4-1) especially. With a 2.73 car, the stock tuning is such that you can get a downshift to 1st gear at up to about 37mph, but something occurs in the ~31-33mph range that sometimes prevents (about 50% of the time, in my experience across several different 4L60E applications in these cars) a downshift to 1st at WOT when the selector is in OD. Above that speed the downshift occurs just fine. On the other hand, when the shift selector is in 3rd, the 3-1 downshift will occur without issue every time up to about 37mph, even in that odd ~31-33mph range.

I tested this with one of my 3.23 cars (these won't go back to 1st at anything higher than 29-30mph with stock tuning) by upping the downshift speed in the tune, to match that of the 2.73 cars. Sure enough, same issue; some sort of weirdness in that 31-33mph range when going WOT in OD, but no issues with the downshift above that. And the with the selector in 3rd, no issues at all.

This has been my observation with several stock 4L60Es as well as a "built" unit, in more than one LS1 F-body, so it's not a fluke that was specific to a single car or transmission.

Mongoose350

iTrader: (1)

I would assume this is the torque managment or something similar, taking precautions to prevent possible damage.

TXZ28LS1

iTrader: (5)

For daily driving i just keep it in OD... if i were to get on it than leave it in D.

Just dont feel comfy dropping it to 2nd than manually shifting it..lol.

RPM WS6

iTrader: (3)

Removing/reducing TM didn't have any effect at all on the erroneous shift behavior in OD in that narrow MPH window.

SPRAYED 01

iTrader: (22)

Ill give Chuck a call, I know to only use d when drag racing. My tbrake wont work in any other gear. I am going to experiment with some trans tuning. I want to see if I can make d stay in 3rd gear no matter what and not downshift. I did some mexico runs and even at 75mph if in d it will go to 2nd then right back to 3. Seems not needed at all.

Plus if I did even a 50mph race and stayed in 3rd I may have a chance of not blowing the tires off with 20psi boost.

mrvedit

You can tune the max downshift speed for each gear at a dozen different throttle positions.
I set my 2->1 max downshift speed at most throttle positions to just 10mph because unless I am nearly stopped I never want a 2->1 downshift.

LS6427

iTrader: (2)

Upgrade to a $400 junk yard 4L80E and about $300.00 in new parts and basic rebuild.........case closed.....LOL

I always did 40-50 mph roll ons in 2nd gear....then went WOT and popped it into D before the PCM shift was going to come. It was a MUCH better hit than being in D.......

.

SPRAYED 01

iTrader: (22)

Ok made a sweet trans tune change today. Before my 3-2 downshift would occur even up to 78mph. I lowered that to 50 mph. So now when I'm in d3 (race mode!) And I'm above 50 mph it stays in 3rd and does not downshift.

With my car being boosted with a ton of power on tap this is huge. I hit it tonight at 60mph at about 12 psi boost (about 650whp) and it hooked and took off. No more blowing the tires off because of the harsh downshift.

Now that was the street tires, I'm hoping I'll have the same result with the drag radials and 20psi (875whp)