Shift Times

[BustedTruck]

I read somewhere on this forum that you do not want to go faster on your shift speed than .1 seconds because of gear overlap. Is there any truth to that? I have heared of people zeroing this value. Has anyone done this.

[SSpdDmon]

I read somewhere on this forum that you do not want to go faster on your shift speed than .1 seconds because of gear overlap. Is there any truth to that? I have heared of people zeroing this value. Has anyone done this.
IIRC, zeroing out the table disables the shift learning in the trans. Also, I believe it's 0.15ms that you don't want to go faster than. What does the description box say when you open the table?

[ScarabEpic22]

Ive heard you dont want to 0 them, keep them above .1, and above .15. Personally on my 02 4L60E (stock plus vette 1-2 servo) I run 0 shift times and 0 TM all around, lowered the BP for the 1-2 because otherwise it was really harsh. Shifts firm all the time, regardless of TP (not brutally like before though).

Yes 0ing the tables does disable shift adapt.

[BustedTruck]

Thanks for the reply. Efi does not specify not to go below .1. How long have you had yours set a 0, Scarab. Have you noticed any ill effects? I am installing the corvette servo this week. Does anyone know for sure about the
shift times?

[Chevy366]

Read this and see if it helps: http://forum.efilive.com/showthread.php?t=1723&highlight=shift+times

[ScarabEpic22]

Been at 0 steadily for the past 6-7 months, before that I would play between like .1-.2 but could never get it right so I 0ed them and 0ed the TM. Remember though, I have the 4.2L I6 not a V8 so 0ing them might not be the smartest thing to do out of the gate. Start by lowering them and see how you like it.

[BustedTruck]

That was some good reading. I have lowered mine to .1 and I like it. My concern was some type of gear overlap when the shift times were at 0, but there seems to be alot of people setting theirs to 0. So maybe its fine.

[Chevy366]

That was some good reading. I have lowered mine to .1 and I like it. My concern was some type of gear overlap when the shift times were at 0, but there seems to be a lot of people setting theirs to 0. So maybe its fine.
I myself have mine 0-ed but I have 4L80e with a TransGo shift kit .
I did zero the shift time in my wifes TB (4.2L , 4L60e) and no ill effect , yet , we have a 5 year warranty so GM would pay for it if something did go wrong , when I tune for others I explain and ask before 0-ing .
They say anything under 3 disables adaptive shift learning , in the 4L60e .

[joecar]

That was some good reading. I have lowered mine to .1 and I like it. My concern was some type of gear overlap when the shift times were at 0, but there seems to be alot of people setting theirs to 0. So maybe its fine.Hi BustedTruck,

The 4L60E, 4L80E, and quite a few of the "traditional" transmissions, follow this principle: during a shift, the hydraulic circuit applying the servo for the next gear also releases the servo for the previous gear; i.e. the applying and releasing components are sequenced by one hydraulic circuit.

So, for the 4L60E:
1->2: 2ND CL fluid applies the 2nd servo (which applies the 2/4 band);
2->3: 3-4 CL fluid simultaneously releases the 2nd servo and applies the 3-4 clutch;
3->4: 4TH fluid applies the 4TH servo (which applies the 2/4 band);

Similar thing with the 4L80E.

So, the concern is not whether the appling/releasing components overlap (they do), but to minimize the amount of time that they do overlap;

when overlap time is long (slow shift time): shift is softer, apply component ramps up (initially slipping until it grabs), release component ramps down (slipping as pressure is reduced until it is free); this ramp up/down slipping during the overlap period causes the "wear" sludge you see when you remove the pan; by minimizing the overlap period, you minimize the wear;

when overlap time is short (quick shift time): shift is harder, the apply/release components slip for less time during their ramp up/down; the concern here is that the shift will be harder; if line pressure is not sufficient, the appying component will slip past the overlap period; if line pressure is sufficient, then the drivetrain will be jerked (which may eventually cause mechanical breakage);

the electronic transmissions (4L60E/65E/70E, 4L80E/85E, 4T40E/45E, 4T65E, 4T85E...) are setup to mechanically shift as fast as possible, and the PCM "slows" down the shift to provide a suitable shift "quality" or "feel";

the older transmissions (700-R4, 200-4R, THM400, THM300, THM180...) were setup to mechanically provide suitable shift timing to meet suitable shift quality; shift kits replaced various springs/valves to shorten the shift time and increase the pressure to provide a "performance" shift feel.

The new generation electonic transmissions (6L80/90) time the applying/releasing components purely by computer algorithm; the pro of this is that it replaces a whole bunch of valves/springs/checkballs with extra solenoids; the con of this is that if the algorithm is tampered with (or an electronic circuit fails or partly fails) then incorrect timing will directly cause mechanical damage.

Cheers,
Joe
:cheers:

[Biggsy]

Hi BustedTruck,

The 4L60E, 4L80E, and quite a few of the "traditional" transmissions, follow this principle: during a shift, the hydraulic circuit applying the servo for the next gear also releases the servo for the previous gear; i.e. the applying and releasing components are sequenced by one hydraulic circuit.

So, for the 4L60E:
1->2: 2ND CL fluid applies the 2nd servo (which applies the 2/4 band);
2->3: 3-4 CL fluid simultaneously releases the 2nd servo and applies the 3-4 clutch;
3->4: 4TH fluid applies the 4TH servo (which applies the 2/4 band);

Similar thing with the 4L80E.

So, the concern is not whether the appling/releasing components overlap (they do), but to minimize the amount of time that they do overlap;

when overlap time is long (slow shift time): shift is softer, apply component ramps up (initially slipping until it grabs), release component ramps down (slipping as pressure is reduced until it is free); this ramp up/down slipping during the overlap period causes the "wear" sludge you see when you remove the pan; by minimizing the overlap period, you minimize the wear;

when overlap time is short (quick shift time): shift is harder, the apply/release components slip for less time during their ramp up/down; the concern here is that the shift will be harder; if line pressure is not sufficient, the appying component will slip past the overlap period; if line pressure is sufficient, then the drivetrain will be jerked (which may eventually cause mechanical breakage);

the electronic transmissions (4L60E/65E/70E, 4L80E/85E, 4T40E/45E, 4T65E, 4T85E...) are setup to mechanically shift as fast as possible, and the PCM "slows" down the shift to provide a suitable shift "quality" or "feel";

the older transmissions (700-R4, 200-4R, THM400, THM300, THM180...) were setup to mechanically provide suitable shift timing to meet suitable shift quality; shift kits replaced various springs/valves to shorten the shift time and increase the pressure to provide a "performance" shift feel.

The new generation electonic transmissions (6L80/90) time the applying/releasing components purely by computer algorithm; the pro of this is that it replaces a whole bunch of valves/springs/checkballs with extra solenoids; the con of this is that if the algorithm is tampered with (or an electronic circuit fails or partly fails) then incorrect timing will directly cause mechanical damage.

Cheers,
Joe
:cheers:

Hey Joe, you should change your name from Joecar to Joetrans! :D

[ScarabEpic22]

No kidding! Thanks for the extra info joe, every little bit helps!

[joecar]

Thanks, you're welcome... anything to help, and every bit helps... :cheers:

[BustedTruck]

Thanks. Wow very informative. Thanks for the information.

[Wasted Income]

Fantastic info, Joe! Thanks.