aifilaw

Part 1

After searching this forum I found no comprehensive list, or rather almost no information at all regarding transmission tuning. After fighting my way through my own debugging and getting explanations I opted to make a explanation guide of all I learned about programming the LT1's 4L60E transmission tuning. I used the C.A.T.S. Tuner and EE Datamaster, but I suppose any scanner and programmer would work, its the fields you work with, not the program.

Before I begin I have to say, once the frustration passed, I was overly excited at the world of prospects that opened up. I'm an old hand at Chrysler BB's. I'm used to changing my driving habits based on a tranny, typically a 727, and occasionally when I entered the chevy world a T-350...still can't stand to work on Ford's, much less drive most of them...
But after some fiddling, and realizing the world of opportunity, that I could actually make the transmission change to suit my driving habits and needs as opposed to the other way around. In fact with both changing I could complement the two....I bet I could eak two more tenths out of a quarter with tranny tuning alone, or time off of a skidpad, roadcourse or autox.
Don't be daunted, it's really quite simple...

So, you've changed the gears in your differential, or tire size, or your cam and you just know that the powerband moved....well shouldn't your shift points? Why is your car shifting when your manually moving it and you don't want it to yet? All these will be answered, hopefully in a way you can understand.

You can skip all of this if you have a data-logger, just record...go for a spin and go WOT, it'll be good to get a 2%ish gear shift baseline as well, and probably manually shifting the transmission as high as you can.

Step one, find out your baseline...
Let's start with tire size, find a good converter. We'll take my setup, 245-50-16 tires, a 3.23 rear differential ratio, and a 4L60E 4-speed automatic transmission... we'll what does that mean.
A quick google search will give you a calculator that can find the diameter of your tires, you will need this.
Tire diameter in inches = 25.65
The 4L60E has gear ratio's as follows:
1st = 3.059
2nd = 1.625
3rd = 1.00
4th = 0.696

Now find calculators for finding mph based on engine RPM and tire diameter. There is one on this site.

The last bit of information you need is when you want to shift...if it's stock I'm sure you can find a dyno of a stock setup, if it's not then perhaps you had it done, or someone can guestimate. We will use my numbers just for kicks...I make max power right at 5500 RPM. Which for me and my case I want to shift in every gear at about 5500 RPM. (I realize there's plenty of reasons for dragstrip use shifting much prior to that in the 1->2 change, power bandwidth, etc....lets just assume 5500rpm in every gear)
Armed with that calculator I can detirmine with 25.65in diameter, and 5500 RPM in 1st gear which is 2.48 and a rear end ratio of 3.23 that gives me shifting points in mph, which the PCM uses because...well....someone was daft..
1st->2nd = 42mph
2nd->3rd = 80mph
3rd->4th = 187mph

Unfortunately, and this is IMPORTANT!!
There are two more things to consider....first, its an automatic transmission...that's about 10% loss, and however big an aftermarket torque converter you have on there (if any). Let's take a wild guess at mine, it's a 2500 converter with a lockup and a 2.5 multiplier, I'll guess 10%
If your running a stock converter and transmission your loss will be more like 5%, and about 250RPM

Some multiplication gives us some new numbers...
42 - (0.10 * 54) = 38mph
80 - (0.10 * 80) = 72mph
187 - (0.10 * 187) = 160mph
You will notice that I rounded the numbers down afterwards, it is better to ere on the conservative side, trust me, I hit the rev limiter enough times to make me cringe doing this.

Second consideration, if you are making more power than stock, or even stock, there is a delay between when the computer decides it is time to shift, and when the shift actually occurs (add 1-2mph), and there is a delay in the transmission slippage so your engine RPM and the speed will continue to increase for a little while after you shift, both of these get worse the power power you add and the heftier your torque converter...This gets lessened the further you go in gears, you have more momentum, and chances are more transmission fluid pressure backing each shift, I would suggest doing the full subtraction to 1-2, half at 2-3 and leaving 3-4 alone.

Now you are armed with all the information you need, time to start editing files....

First thing is First, ECM Constant Table!!!
Changes that need to be made and why:
Fuel Cutoff speed - Change to max (255mph), why would you want a limit on how fast you can drive??
Fuel Resume Speed - change to near max (253mph), just to get it out of the way
Fuel Cutoff, 1st gear (this is your first gear rev limiter...200rpm is good for a stock engine past your shift points you calculated or discovered, more depending on your engine mods and converter, I put the rev limiter at 6400 because I know the block can handle it)
Fuel Cutoff, 2nd - 6th Gear - (same thing)
Fuel Resume, 1st Gear - when it starts feeding your engine with gas again after it bounced off of the rev limiter, make this at least 100 rpm lower than your cutoff or if you are foolish enough to keep your foot in it, or throttle gets stuck, it will sound horrible and be worse for your engine
Fuel Resume, 2nd - 6th Gear (same thing)
Low PRNDL Upshift Speed Threshold - Change to maximum (255mph), make it shift when you want it too, remove the limits
Low PRNDL Downshift Speed Threshold - same
Maximum Line Pressure - (This is the maximum transmission fluid pressure for your transmission, stock is 90psi, mine is 120 with a shift kit, a new converter, and some other work such as new bands and lines, etc to handle it....more pressure means firmer faster shifts, it also means lower tranny life....this does not mean your tranny will be hitting 120 psi the entire time, we'll cover this later...it just means it will never ever ever go beyond 120psi)
Kickdown Mode Enable TPS Threshold - (set to low 90%) this will make the PCM use the kickdown mode tables only if throttle is beyond this percentage (This is now known as WOT Mode for some programs)
Kickdown Mode Disable TPS Threshold - (set in the upper 80's) this will turn off kickdown mode tables and go back to other tables for shifting (This is now known as WOT Mode for some programs)

That's it for the ECM Constants table.

Wow, so many different tables...do I need to change them all? what do I change them too?
There are 5 different shifting modes - normal, performance, manual, cruise, and kickdown.

Performance is used when performance mode is enabled (firebird switch)

Manual is used when the gear shift lever is in a position other than overdrive

Cruise is used when you have cruise control activated

Normal is used most of the time

Kickdown/WOT is used when your throttle is above the enable TPS threshold value you set in the ECM constant table and hasn't dropped below the disable threshold value. There are mph and RPM tables....the reason is they BOTH MUST BE MET TO SHIFT!!!
If one is some absurd number like 8000 RPM, you can be over 40mph all you want, it will never shift and bounce off the rev limiter. If it's set at 4000 RPM and the other is set for 5 mph, it will shift at 4000 RPM, because that is when they are both true. Both must be true!!

Kickdown/WOT mode tables has hot, cold, and normal...when it's at normal operating temp, it uses normal, when it's hot, it uses hot, when it's cold, it uses cold.



Below will be listed in bold the different tables, then their description and what they do, followed by how to set them up.

aifilaw

Part 2



(Normal/Performance/Cruise) Mode UP/DOWN Shift Points

This is normal mode, most driving will occur within these, they are pertty important, I know most want to skip to WOT mode...but fact is you don't spend your life in WOT, and changing this table will make driving a lot more fun...scratching the tires at 30% throttle acceleration from 1st to 2nd......it can happen...reduced tread life too

I note from the original table that 0 TPS is set at 11mph, I take the new value 38mph and insert it at 100% TPS and then go about filling in the table...I suggest following the rate of change pattern the previous table had...or simply making it linear....the linearity or exponential rate at which you increase or decrease as long as you stay within those numbers changes how your vehicle drives, keeping numbers low (slope low) at the beginning rates makes your car shift less abruptly, sooner, ramping the numbers higher means it must reach that speed before the shift at that throttle position, it will yield in harder more abrupt shifts...with enough torque it will have some entertaining effects.
setting up the 2->3 table happens the same way, 20 for the min, 72 for the max, fill them in.
same with 3->4 table, 28 for min 160 for max.

It's important to note that unless you set up the kickdown/WOT mode in the ECM constant table to unreachable values, the last two or three fields in this table will never be reached, but it is a good reference point by which to base the other numbers so the transition is not street beast to daily driver.

now the downshift table....here it is good to set a maximum somewhere in the midrange of the min and max of the gear you will be shifting too, for example for the 2->1 table, take the maximum and min from the 1->2 table, take the middle, "20" and use that as the maximum TPS number for the field, I'd suggest a realistic number for the other, like 10. Fill in as before
same with 3->2, halfway between 72 and 20 is about 45, set as max, use 20 as the min, fill it in
same with 4->3, halfway between 160 and 30 is about 100, set as max, use 20 as min, fill it in.

Really these are general guidelines to get you on the road, playing with these numbers is as simple as thinking to yourself, if I was at 1/4 throttle (25%) in second gear, and pressed the throttle down to 50%, what is the maximum speed I want to be going for it to downshift?
Same theory with upshifting, with this much throttle, at what speed would I want the tranmission to shift to the next gear?



Manual Mode UP/DOWN Shift Points

This has its own special area in this post because manual mode should be just that...manual, you have a rev limiter for a reason, if you hit it, it's your own stupid fault...if you can't stop hitting the rev limiter because you don't know when to shift, stop using manual mode.

Shift points for this field should be as follows.
1->2 field, fill in with 0
2->3 field, fill in with some rediculous high number over 200, like, 200
3->4 field, fill in with 200
2->1 field, fill in with 0
3->2 field, fill in with 200
4->3 field, fill in with 200

Done.


(WOT/hot/cold) Kickdown Mode UP/DOWN Shift Points

Kickdown/WOT mode tables has hot, cold, and normal...when it's at normal operating temp, it uses normal, when it's hot, it uses hot, when it's cold, it uses cold. I suggest keeping hot and normal the same, and going under by a several mph in the cold field

This field and the RPM field are what detirmine your WOT shift time!!

Very simple, take the number you calculated earlier for mph of each shift and enter it.
This is the Wide Open Throttle speed at which these gear shift events happen if and only if the RPM settings in the corresponding table are met as well. If it's downshifting, it will only look at MPH.
Mine were as follows:
1->2 = 38mph
2->3 = 72
3->4 = 140
2->1 = 20
3->2 = 45
4->3 = 100


(WOT/hot/cold)Kickdown Normal Mode Shift RPM Thesholds

Kickdown/WOT mode tables has hot, cold, and normal...when it's at normal operating temp, it uses normal, when it's hot, it uses hot, when it's cold, it uses cold. I suggest keeping hot and normal the same, and going under by a several hundred RPM in the cold field

This field and the mph field are what detirmine your WOT shift time!!
Very simple, take the number you calculated earlier for RPM of each shift and enter it.
This is the Wide Open Throttle speed at which these gear shift events happen if and only if the MPH settings in the corresponding table are met as well.
Mine were as follows:
1->2 = 5500
2->3 = 5500
3->4 = 5500



Main Line Pressure 0-64MPH

Main Line Pressure changes the hardness and speed of the shift, there are two tables that have basic effect on that, this field for 0-64mph, and the one mentioned after these. This is the foundation, the basis by which that field is made.

These numbers will never in actuality exceed the limit you set in the ECM Constants Table earlier no matter what you set them for.
I highly suggest simply incrementing each TPS Line of the table at the same rate and keeping the same ratio betwixt them, You can seriously damage or destroy your transmission by setting the line pressure values too high. If yuo don't care and you take it drag racing, then max it out at WOT and ramp it on the rest, will yield in an easy way to build RPM's and pressure for the launch.


Main Line Pressure 64-128MPH

Main Line Pressure changes the hardness and speed of the shift, there are two tables that have basic effect on that, this field for 64-128mph, and the one mentioned after these. This is the foundation, the basis by which that field is made.

These numbers will never in actuality exceed the limit you set in the ECM Constants Table earlier no matter what you set them for.
I highly suggest simply incrementing each TPS Line of the table at the same rate and keeping the same ratio betwixt them, You can seriously damage or destroy your transmission by setting the line pressure values too high. If yuo don't care and you take it drag racing, then max it out at WOT and ramp it on the rest, will yield in an easy way to build RPM's and pressure for the launch.


Line Pressure Offset vs. TPS% vs Gear (Normal/Perf/Manual)

Increases the line pressure at a exact numerical rate based on throttle position. So if for example at 50% throttle at 30mph I have set the vehicle to shift, main line pressure comes from 0-64mph table which is 76, add the number from this table which is 59, and you get 135....which is higher than the 120 I have set, so the line pressure will be 120....I need to change that....


Shift Time (sec) Vs. %TPS Vs. Shift, (Normal(high alt/low alt)/Performance(high alt/low alt))

Those shift speed tables are supposedly used by the PCM for adaptive shifting. For example, if the shift time is longer then the value in the table, the PCM increases line pressure to execute the shift more quickly. But most performance tunes (and even the factory tune under some circumstances) already have the line pressure maxed out at various shift conditions.

So, some tuning articles I have read say you can adjust the shift firmness by changing the values. But in my experience changing those values seems to have little impact. And, the professional PCM tuners do not change those values, instead choosing to change the Line Pressure Offset (psi) Vs. %TPS Vs. Gear (normal/performance) tables. I believe this is because modifying the line pressure offset table results in a more consistent, and repeatable shift profile.


TCC (Normal/Performance/Manual/Hot/Cruise) Engage MPH Vs. Gear Vs. %TPS

These tables are based on when the lockup converter enables, set these values for good fuel mileage at cruise speeds. If you have a big lopey cam that doesn't make power below 2000 RPM, better make sure you don't set it in a gear at a MPH speed lower than that RPM or you will have a bumpy and inefficient ride.

All values you don't want a chance of the converter coming on or off, set to 255



TCC (Normal/Performance/Manual/Hot/Cruise) Release MPH Vs. Gear Vs. %TPS

These tables are based on when the lockup converter disables, make sure that the numbers are less than the corresponding enable number, or you may lock your converter on.

All values you don't want a chance of the converter coming on or off, set to 255




A big thanks to vgeglia for helping me figure a lot of this stuff out. I found almost nothing regarding these tables and how they worked and why doing searches on the site or on the web. If any of this information is wrong let me know and I will fix it so the next person who does a search for "Performance Mode UP/DOWN Shift Points" trying to set his WOT shift times or someone who has piddled with it is bouncing off the rev limiter and scratching their head comes across it and gets good information.

shoebox

We have a 4L80E?

Curious about the shift time table. My stock tune has the performance mode set with all values at 6.375. From what I read above you say that is slower [than 0.750]? Any idea why they would put slower shift times in the performance mode? Doesn't make much sense to me.

aifilaw

Fixed the 4L60E...

I don't know exactly what that number means, but I believe it controls the speed of the shift,
I notice that the performance mode 1->2 transition is 6.75 whereas the 1st gear is 0.75 on my own stock PCM file.

I can account for this by noting the Line Pressure Offset (psi) Vs. %TPS Vs Gear (normal/performance) tables

you will note line pressure is significantly higher in performance mode, and that should speed up the shift without having to modify the table...just a guess at what GM is doing...

sbs

All of this has been discussed years ago on other boards by people who know a lot more about it than you or I.

I'll try and find some of the links and post them.


You seem to be saying that there is a 10% converter slippage before the shift. Typical slippage in my 4L60E behind my stock LT1 before a WOT shift is less than 5% ( Usually around 250 +/- 50 rpm slippage at 5000 rpm)


In a stock tranny, the max line pressure setting doesn't do much. The software can't make the hardware produce more pressure. The "Main Line Pressure" tables are where the action is for a stock tranny.

OTOH, with a modified tranny, I have always seen it recommended (by transmission builders) to leave the line pressure in the software alone. They say either change the software or the hardware, but not both.


Typically people use either the MPH or the RPM settings, not both, so they can have precise control over the shift.


Wrong. Harder, quicker shifts are better for the tranny.

VinceTrifecta

Those shift speed tables are supposedly used by the PCM for adaptive shifting. For example, if the shift time is longer then the value in the table, the PCM increases line pressure to execute the shift more quickly. But most performance tunes (and even the factory tune under some circumstances) already have the line pressure maxed out at various shift conditions.

So, some tuning articles I have read say you can adjust the shift firmness by changing the values. But in my experience changing those values seems to have little impact. And, the professional PCM tuners do not change those values, instead choosing to change the Line Pressure Offset (psi) Vs. %TPS Vs. Gear (normal/performance) tables. I believe this is because modifying the line pressure offset table results in a more consistent, and repeatable shift profile.

sbs

I was trying to find a good reference on this. Best I came up with right now is

http://www.monodax.com/forums/1954-post9.html


Basically, they are not really a "shift time" but rather a parameter for an adaptive routine.


I've seen basically the same info from other people with lots of 4L60E tuning experience, so it seems credible, although I'll be darned if I ever noticed any learning going on. With the stock settings it had crappy shifts when the computer was reset and still crappy months later...

VinceTrifecta

Cool, thanks for sharing steve9899.

sbs

I was just searching through my bookmarks and Google trying to find which site I had found the useful discussions on 4L60E programming a while back.

I _think_ it was on the LT1edit mailing list archives, which unfortunately are impossible to search online. Basically the best way to muddle through them is to download the archives then import them into a mail reader and search using the mail reader. The discussions I'm referring to were old when I found them, so I'd look back maybe to the 2001-2002 timeframe.

This was the only 4L60E discussion I ever found (assuming it was on that list...) where there were some people who actually seemed to know how the software worked, as opposed to making guesses about what is in the black box.

aifilaw

By the very fact that you have trouble finding them, or have to sort through archives unsearchable is the very reason I posted this.

I didn't pretend from the beginning to fully understand most of this, but since those who do have not done such a comprehensive guide, I thought I would help the rest of the hackers and tuners get a better understanding as I did. Which is why I am editing the post pages to include changes and information.

Using just the MPH setting and setting the RPM to arediculous setting, will mean it will never shift in kickdown/WOT mode. I've tested this, and vice versa...it must be a logical AND operation.

Posts have been edited thus far from comments, thanks for the help.

aifilaw

Re-edited to fix information

sbs

There's nothing in this thread so far that isn't easy to find in dozens of places on the web.

I agree with your motivation to have a reference thread. However, I'm opposed in general to beginners providing "reference information". Doubly so when we are talking about modifying transmission parameters that can cause physical damage if done incorrectly.

I don't know enough about 4l60E programming to provide such a reference thread, and from your posts I'd say I know a lot more about it than you do.


You are correct that it is an AND. Most people set one to always be true. (For instance, I use rpm for WOT shifts, so my WOT shift mph are set at 10mph for all gears.)

aifilaw

If it was so easy to find, why did I waste half an hour doing searches on this board, and on the web for obvious keywords such as tables and values and come up empty-handed only to have to learn it on my own.

If you are opposed to a beginner writing a referendum about what they learned, then where is the "expert" writing a full and complete guide both at a beginner level which I've attempted, and an advanced one explaining all tables and how they effect the transmission.
If any of the information here is incorrect, then I have, and will continue to change it if someone points that out to me. If it is correct, and you don't like that a beginner posted it...I could care less, deal with it. If you know more about it, then you write a transmission tuning tutorial.

I appreciate your help, I wrote this to HELP others.

indieaz

Really? Please post such links. When i still have my f-cars i spent much time searching - coming up empty handed - for tuning information. Information is scattered all over in various threads etc.

If there's all this information so easily found doing web searches, how baout posting some links and a sticky can be made? It wouldn't be a bad idea for a place like the tuning forum to have a few sticky's for various tuning functions so people don't have to search.

sbs

That model would work fine if there was already someone here who had both expertise in 4L60E programming and a willingness to share that knowledge. There has been no such person here in the four years I've been reading this board.

Since we don't have such a person, then some of your incorrect information may remain here, posing as fact, for some innocent noob to come along and use and blow up his tranny.


You searched for a whole 1/2 an hour?

You haven't "learned" much of anything. You've tweaked some parameters, mostly blindly, and observed what some of the effects are.

How many miles do you have on the tranny with your line pressure and shift time changes? How long will it last with them? You've modified one tranny and used it very little since you made the changes. You know almost nothing about the effects of those changes.

One of the things you did - change line pressure in both software and hardware - has been mentioned as a sure way to kill a 4L60E by people who do have extensive experience modifying these trannys. (I am not one of them, so I'm just parroting what they have said about this.)


I also could not care less about your opinion. I have posted here not for you but so that when that innocent noob comes across this thread he will be forewarned that you have little knowledge of what you are writing about.

Since I think I've accomplished that, I'll stay out of your thread now.