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Transmission Tuning Tutorial

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Old 03-14-2007, 09:19 AM
  #46  
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Originally Posted by aifilaw View Post
Ok, after looking over a couple of tunes, including one by pcm4less for my tranny I came to a few conclusions.
They completely left alone the "Line pressure modifier in WOT vs RPM" table and instead resorted to modifying the other tables to increase line pressure so it would reach the new 120psi maximum.

They also left alone the "Line pressure mod vs %TPS vs Trans temp xxxx" tables which are effectively meant to keep your transmission from self-destructing due to temperature.

The Main Line Pressure 0-64 and 64-128mph tables are one of the two step method I am seeing as used to increase the line pressure on the "performance" transmission modifications to make the most of them. But the 0-60 and 60-128 tables seem to be just the start. and instead of using the "Line Pressure modifier in WOT vs. RPM" tables (either because it doesn't work, or otherwise unknown to me) it seems the prefered method is the "Line Pressure Offset (psi) Vs. %TPS Vs. Gear"
Which is really a much better way of doing it, as the 1st->2nd shift is probably the most important.

This table on mine was heavily modded by the tuner, and I haven't touched it. but I must say it does the trick, and like I mentioned before, my transmission hasn't suffered from it, in fact the firmer shifts are probably extending it's lifespan. The most important thing of note, is that the modifier is set to "95" which will probably ensure it is maxed out at 120psi from 62.5% TPS to 100 in every gear to ensure pressure is set as high as it can. 0-25% TPS are zero'd in every gear. Honestly this makes sense if you are familiar with kickdown linkage on old transmissions, a lot of drag racers would just wire their kickdown linkage full on, since it wasn't used on the street and they wanted every shift at maximum pressure it made sense to do that. the rest of the table is slightly scaled as shown here.....pasted below that is the stock settings for a '94 camaro for reference.

0 0 0
0 0 0
0 0 0
0 0 0
12 12 12
24 24 24
36 36 36
48 48 48
59 59 59
72 72 72
84 84 84
95 95 95
95 95 95
95 95 95
95 95 95
95 95 95
95 95 95


0 0 -10
0 -2 -2
-2 -10 -8
-4 -8 -8
-4 -6 -2
0 -7 -4
-1 -9 -3
-4 -14 -10
-1 -15 -11
-2 -16 -12
0 -15 -13
0 -12 -10
0 -15 -1
0 -11 6
0 -13 6
0 -11 6
0 -11 6


You could probably get away with leaving your 0-64 and 64-128 tables alone and just do your main adjustments with these tables. I'd assume that the WOT table does nothing since it is zero'd out and my tranny still reports full line pressure at WOT.
Is the top one moded and the lower one stock?
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Old 03-14-2007, 09:22 AM
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yes, top one is modified, lower table is stock
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Old 03-14-2007, 09:59 AM
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[

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....


My 1st to 2nd shift is alot firmer than 2nd to 3rd so I went in to the tables where it shows the two pressures at both shifts and it shows the two pressures being the same at 68 psi. Why isn't the shift the same firmness?
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Old 03-14-2007, 10:07 AM
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2-3 shift is the "softest" shift in the 4L60E due to its design mechanically. It has something to do with how the 1-2 shift has a dedicated accumulator but for 2-3, it does not. I understand a 2-3 shift is more complicated, too - it has to pull off the 2-4 band and apply the 3-4 clutches to in order to make this shift.

In my 99 Z28, which is stock, it shifts so hard out of first it chirps the tires, but it won't do that from 2-3.
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Old 03-14-2007, 10:34 AM
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Originally Posted by vgeglia View Post
2-3 shift is the "softest" shift in the 4L60E due to its design mechanically. It has something to do with how the 1-2 shift has a dedicated accumulator but for 2-3, it does not. I understand a 2-3 shift is more complicated, too - it has to pull off the 2-4 band and apply the 3-4 clutches to in order to make this shift.

In my 99 Z28, which is stock, it shifts so hard out of first it chirps the tires, but it won't do that from 2-3.
Oh, I was thinking that maybe the Shift time(sec) Vs. %TPS Vs. shift, normal mod, low alt might have something to do with the shift firmness.
Is this the time it takes for the shift to take place?
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Old 03-14-2007, 10:59 AM
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I assume that it is, but the time value is not in anything I can understand (mS, uS, S), it is probably in clock cycles.

vgeglia is correct, mechanically the 1-2 will be firmer than the 2-3 shift...
this happens for the reasons he mentioned, and the fact that you already have a vehicle in motion with far more momentum at 70mph than you had at 40mph, therefore physically it would require more torque from the engine to provide as firm a shift in the 1-2 as in the 2-3....
lastly if you subtract the difference in gear ratio's of 1st gear minus 2nd gear that number will be significantly higher than 2nd gear minus 3rd gear...meaning the difference is greater for the step-down which will provide a much less firm shift.

Couple those with the extra mechanical time and effects of the transmission on the 1-2 vs the 2-3 shift, and you will get a much less firm feeling shift from 2-3 as you will from 1-2 regardless of line pressure.
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Old 03-17-2007, 10:29 AM
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Thanks for all the info guy's! I'm sure i'll have more questions once the wheather clears up and I get a chance to run some of these files I made up. I realy appretiate it.
Later on i'm going to try playing with my fuel trims, after I get my shifts straightend out.
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Old 07-15-2007, 01:47 AM
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Pretty wild to see some of the stuff we did over seven years ago being gone over again.

here is a link to some stuff we wrote up years ago. I have learned alot more since then but never had the time to write it up. I have found many year to year changes and other veriables. I have answered many of the ????????????? answers since then

As far as doing internal and PCM changes? We do both in many cases. In some cases one just will not work with out the other

Many of the tables we have to work in today are from work we did back then. had the LS1 not taken over so fast we could of had much more. The developer left us out in the cold at times after the LSx stuff hit and I have no way to hack code

BTW I run a 97 PCM for faster more reliable control over my transmission...My engine seems to like it also

Enjoy guys!

Last edited by OneFlyn95z28; 07-15-2007 at 02:23 AM.
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Old 07-15-2007, 03:35 PM
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Thanks for the info OneFlyn! I enjoy the hell out of this stuff.
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Old 08-05-2007, 11:58 PM
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would this trans tuning be the same for LS1 4L60E?
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Old 08-06-2007, 01:44 AM
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More or less... Some of the table names changed, and things like line pressure are driven by engine torque output calculations instead of throttle position, but the basic premise is the same.
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Old 08-14-2007, 05:24 PM
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I have read alot of this, and man I am lost as ever. i am just wanting to firm up my shift maily at wot. Does anyone have a tune I can look at to compare. Stock tranny with 3:73
wanting to help out at the track. Im using tunercats also.
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Old 08-14-2007, 05:30 PM
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In many cases, the maximum line pressure is commanded at WOT with factory tunes anyway, so increasing WOT firmness is not possible without a shift kit.

Can you post your Main line pressure 0-64 MPH & 64-128 tables along with the line pressure offset (normal mode) table? We can look at that and see what you're set up with.
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Old 08-14-2007, 06:50 PM
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I have 2 diff tunes, one says it is factory, and one has been moded, but not sure if it is right. have files if you want to look at them
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Old 08-15-2007, 06:38 PM
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Willing to bet the stock tune has it maxed well beyond 90psi, which it is regulated at from the constants table. Raising that constant probably won't do anything on a stock transmission.

You can firm your shifts a little by adding line pressure to your below WOT tables... but at WOT, it should already be maxed out, just lower your shift times table and that's about all you can do without modifying the valvebody, and/or pump.
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