Some LT1 4L60E transmission tuning observations (8051)

[sherlock9c1]

I'm not trying to start a debate here; and there's no question that a stock 4L80E will handle more input torque than a stock 4L60E. All I'm trying to do is offer some LT1/4L60E tuning tips. After I rebuilt and beefed up the 4L60E in my car, I've put over 50k on it, drag raced (close to 200 runs), road raced for nearly 5 hours in one day, road tripped, everything, and the pan stayed clean the whole time. AFTER all that (and regular fluid changes), the ideal 1-2 shift time was 0.600 seconds. That trans had good line pressure so I didn't need tiny shift times to make it shift good. Other 4L60Es, especially stock ones with high miles, will likely need shorter shift times. It's really going to come down to the individual vehicle and combination.

FWIW, the 8051 PCM can control a 4L80E with nothing other than programming changes (and maybe modifying the trans harness connector pinout).

What I don't want to see is people needlessly raising line pressure in the main tables or raising the "max line pressure" scalar without realizing what they're actually doing.

[Fast355]

I'm not trying to start a debate here; and there's no question that a stock 4L80E will handle more input torque than a stock 4L60E. All I'm trying to do is offer some LT1/4L60E tuning tips. After I rebuilt and beefed up the 4L60E in my car, I've put over 50k on it, drag raced (close to 200 runs), road raced for nearly 5 hours in one day, road tripped, everything, and the pan stayed clean the whole time. AFTER all that (and regular fluid changes), the ideal 1-2 shift time was 0.600 seconds. That trans had good line pressure so I didn't need tiny shift times to make it shift good. Other 4L60Es, especially stock ones with high miles, will likely need shorter shift times. It's really going to come down to the individual vehicle and combination.

FWIW, the 8051 PCM can control a 4L80E with nothing other than programming changes (and maybe modifying the trans harness connector pinout).

What I don't want to see is people needlessly raising line pressure in the main tables or raising the "max line pressure" scalar without realizing what they're actually doing.

I understand on the line pressure thing. There are multiple feed holes that need to be enlarged and numerous accumulator springs that need to be stiffer to get a good shift feel.

You do realize if you are still using torque management and the corresponding timing retard that you are also retarding the timing for 600 mseconds at each shift. On a car that is going to be used Street/Strip I have no problem running 0.00 commanded shift times on ALL shifts to keep the PCM from trying to reduce line pressure. With the 0411 its pretty easy to adjust command shift times and line pressure to give maximum line pressure at high torque production since all the tables are referenced against engine torque. Also keep in mind that a higher stall converter has a cushioning effect on the driveline and to get the same sharp shifting at WOT and more so at part-throttle it will need a quicker shift timing and more line pressure at part-throttle.

My stock as the general built it and tuned it 4L60E lasted about 38,000 miles. Rebuilt with a properly setup Transgo HD2 to 4L65E specs and had a decent tune in the PCM to keep the clutches from smoking and it lasted 44K before hard parts failure. At 82K I swapped a 100K mile used 4L80E in it after installing a Transgo HD2 and B82 4.3 converter.

[Fast355]

The last 4L60E I tuned has a firm 1-2 shift that occasionally spins the tires a little, yet glides around town pretty smoothly despite a somewhat loose 2,700 rpm converter. This transmission is on borrowed time however. Has relatively high miles (85K on rebuild) and sits behind a 330-340 HP L31 that is making somewhere close to 400 ft/lbs of torque and its in a heavy 1999 Suburban.

https://www.youtube.com/watch?v=3RAqXKq1e9Y

[sherlock9c1]

Yeah, the TransGo HD2 kit was good. I really like the Sonnax 4L60E-HP-01 kit even better. It's pricier but it's got a lot more good parts in it.

BTW the 8051 does not have torque management as far as I'm aware.

[Fast355]

Yeah, the TransGo HD2 kit was good. I really like the Sonnax 4L60E-HP-01 kit even better. It's pricier but it's got a lot more good parts in it.

BTW the 8051 does not have torque management as far as I'm aware.

It may have a 1-line type of torque management, similar to the older TBI PCMs. To my knowledge they all have abuse mode torque management that is active under certain conditions. Such as reving the engine above 1,500 rpm and moving the gear selector, such as when rocking a vehicle stuck in snow.

[sherlock9c1]

Huh. I assume nobody's discovered this? (where's steveo) I know the 4L60E itself has "abuse valves" in the forward and reverse apply circuits which bypass the normal apply process under heavy load conditions and provide much more power to the clutch applies to avoid slipping them during these sorts of applications. If those valves get stuck in the open positions in the bore (been there experienced that), you get really harsh shifts into gear from P/N.

FWIW, if you're stuck in snow, don't bother shifting. Automatic transmissions take too long to shift. Just use the gas pedal to rock the vehicle back and forth, but leave it in one gear. Worked every time for me when I was in the snowbelt.

[Fast355]

Huh. I assume nobody's discovered this? (where's steveo) I know the 4L60E itself has "abuse valves" in the forward and reverse apply circuits which bypass the normal apply process under heavy load conditions and provide much more power to the clutch applies to avoid slipping them during these sorts of applications. If those valves get stuck in the open positions in the bore (been there experienced that), you get really harsh shifts into gear from P/N.

FWIW, if you're stuck in snow, don't bother shifting. Automatic transmissions take too long to shift. Just use the gas pedal to rock the vehicle back and forth, but leave it in one gear. Worked every time for me when I was in the snowbelt.

I use 2nd gear start to rock it enough to move. No issue driving around with the limited ice days we have here. Can't stop people from doing dumb things so GM had to find a way to counter them.

I also seem to remember the older TBI PCM cutting timing if you manually shifted the transmission above the factory shift points. I guess the PCM saw that as "abuse"

[steveo]

(where's steveo)

even if i had an lt1 to work on; i've never worked on the automatic stuff, i'm a gear jammer. besides a tiny bit of cleanup and confirmation on the xdf, that is.