I'm sitting here, a pile of papers on my desk, drinking this coffee that my partner brewed up that is like tar.

But I'm thinking about line pressure.

Line pressure is one of those topics that comes up message boards, but I rarely see any conclusive comments in those threads.

I was talking to Mike at Yank today, and I happened to bring up line pressure. I asked him, what is too much? What can you tell me Mike....

He feels that anything in the low 200's is the way to go. He was referring to lbs of pressure measured with a gauge. Mike feels that pressure in the 240 - 300 range can be a problem, and can blow the pump.

So I'm wondering, what is a recipe for disaster. What combos can we tell folks to avoid...

I'm thinking jacking up the line pressure with LS1 Edit or HPP3 + a shiftkit with a whole bunch of washers might cause problems. Doing BOTH might result in huge line pressure.

Now line pressure is jacked up the help make the transmission shift. So it's necessary. Stock line pressure is typically in the high 100's, maybe we can say 175 is normal line pressure, just for the sake of this discussion.

I have been generally reccomending that folks EITHER run a shift kit or play a little bit with line pressure but not to do both at the same time.

Now I would like to know if anyone knows how line pressure is boosted by changing the settings in LS1 Edit or with a HPP3. Are we delaying something or making a pump work harder?

HOLLA!

 

I don't think you can raise the actual max line pressure with Edit. Someone please correct me if I'm wrong about this. You can make it a different percentage of max pressure under different circumstances but not actually change the max pressure. Mike and I talked about this at the Thunder shootout. What he told me about max safe line pressure goes along with what he told you. I recall him saying that 230 was about the limit and that stock was about 175...if memory serves.

Here's something else he told me that's interesting. He said you can check the max line pressure by putting the selector in reverse (we were speaking of a 4L60-E.) The tranny uses max line pressure at all times in reverse because of the limited holding power of the frictions involved. So, a quick test to see if you can actually raise the line pressure with Edit would be to check it stock and then again after Edit. Stock, at idle in gear should say about 45 psi and high 100s in reverse. Mine currently reads 60 psi at idle but I didn't check it in reverse because I didn't know this little trick at the time.

 

I did both at the same time and got a negative result. Trans go with all washers and LS1 edited line pressures and shift times adjusted and the pump went. The bushing on the pump and the front of the pump housing got nuked. Had brass bearing material burned all over the hub of my 950 dollar converter, I got mike to take care of that for me.

I talked with mike, and he said to cause that type of damage the line pressure was probably high 300s. He also mentioned that pressure that high possibly would have cracked open a stock converter. The astronomical line pressure in my stock trans also resulted never-ending trans cooler line leaks. I had TWO hose clamps on barbed fittings and the thing would still leak. After I got my Pro Yank 4L60E that he said runs low 200 psi, it never leaked again. He told me the 175 figure for the stock trans, too. I ended up getting a new transmission, but he did make some recommendations if I wanted to try and salvage the stock one. He said turn all the LS1 edit shifting stuff back to stock. Then remove all of the shift firmness washers and try it. The only two ways to increase holding power is to increase pressure or increase the friction on the clutches.

That being said, think about this for a second. What really happens when you use LS1 edit and adjust the shift times but leave line pressure settings alone? Isn't the computer simply going to raise the line pressure in an effort to cause the shift to happen quicker? That's the only thing it can do, right?

Colonel,
I never thought about the LS1edit not being able to adjust the actual max line pressure. It would make sense to say that the stock programming doesn't use max line pressure for WOT shifts then, right? The shift kit obviously raises the actual max line pressure. That would explain why when you program the car to use a larger percentage of its now higher max line pressure from the shift kit you run into trouble.

 

So if stock pressure is 175 and HPP3 says increase 50% that would be 262.5 and therefore bad? so the only good setting would be 25% increase for 218.75lbs of pressure. Am I doing this right?? If I'm wrong, what do they mean by 25-50-75 and 100% increase in line pressure?

 

"It would make sense to say that the stock programming doesn't use max line pressure for WOT shifts then, right?"

According to LS1Edit, the stock tables are set at 100% at 100% throttle. That's why I don't think you can see and increase in shift firmness at WOT by programming.

I don't think that desired shift time and line pressure go hand in hand. I admit I don't know exactly what has to take place to make a shift happen quicker but I don't necessarily think that the line pressure has to be raised. Elsewise just raising the line pressure would make the shift as quick as it can be. It does seem quicker to a degree when the pressure is raised but that might be due in large part to less slippage. The actual process is still being commanded by the PCM at the same rate. When decreasing the shift time as programmed, it is very noticable how much quicker shifts, especially part throttle shifts, take place. But has the line pressure been raised? I don't think so.

Maybe someone else knows more about this.

 

"So if stock pressure is 175 and HPP3 says increase 50% that would be 262.5 and therefore bad?"

Again, I don't think that programming raises the MAX possible pressure. I think it raises the pressure at different part throttle positions. At a given throttle position (other than 100% where the pressure is already programmed at max) the pressure will be a higher percentage of max pressure when you up the shift firmness via programming.

 

The force motor in the transmission is controlled by the computer, and when ALL current is removed the trans will shift at whatever max pressure is set at build-time. Edit cannot increase line pressure over that, in any way. When you increase your shift firmness in 'edit, you're mainly changing part-throttle shift firmness, where the stock profile allows more slippage. You are able to get a little more pressure at WOT, since the stock tables don't drop all the way to zero.

 

That is absolutely correct! The factory max spec @ WOT is 189 psi. there is no way to increase that figure electronically. Remember, this is the GM MAX. Most units do not run that high. The force motor IS adjustable. But if you do not know where you are to start, how do you know how much to increase it? 1/6 turn of the adjusting screw = 12-15psi. So, you still need a mechanical gauge to get your starting point. 200-205 IS MAX!!
Not only does higher pressure work the pump harder but it also increases operating temps. That is not good either!
Ideally, the kit approch is best. You do not need 225 psi for a tire chirpping shift. What you do need is for the time it takes to drop pressure to the componants holding 1st gear and the time it takes to apply pressure to the 2nd gear componants to be as quick as possible AND that there be no overlap.
The shift kits by Transgo and Superior/Fairbanks and Sonnax have been engineered for those purposes.
There are other longevity issues that these companys address as well, like a stronger stator support shaft, front pump pressure regulator valve, TCC apply valve and TCC solenoid snout with anti-drainback feature. That's just in the front pump!
A wide reaction 'sun gear' bushing, double sealed, pinless forward accumulator piston, the famous "Corvette style" servo and so on!
It is no wonder to me that so many trannys get messed up using the hit-or-miss approch with HPP whatever and all the rumors that get circulated on these boards or by some of the "shops' you all have mentioned as messing stuff up.
I would not let anyone modify my tranny who is not current with his ATSG certification on the 4L60E.

 

I decided to return line pressure back to stock after realizing that it doesn't change WOT pressure. I didn't particuarly like the hard shifts at part throttle anyway and you get 100% line pressure at WOT. So why mess w/it?

Now if you could increase pressure at WOT that would probably be worthwhile.

 

The delay is an independant variable that is set using its own table in edit. I have not messed with it as changing the delay will also have a side effect of changing the effective shift point.

FWIW, there are multiple pressure related tables in Edit. Some I have familiarity with, but I have not yet figured out the exact purpose of each table and their inter-relationships.

As brains stated, you can alter the tables to increase WOT pressure above the factory max program because the table itself is not set at zero at WOT. Whether that it is safe, is another story.

 

Using LS1 Edit, rather than trying to increase shift pressure with the Positive Pressure vs. Temp table, firmer shifts are possible by scaling the Base Shift Pressure vs. Torque table up by a minimum of 130%. Changing the values in the Positive Pressure vs. Temp table made little difference to shift firmness. Changing the Base Shift Pressure values made a HUGE improvement to shift firmness

I'm not sure if the Base and Brake Shift Pressure tables make a difference to line pressure, but they do have an effect on shift firmness. You can also use the table to alter the shift pressure for individual gears, rather than effecting all the gear shift changes.

 

One other possible concern with the line pressure is fatiguing of hard components. I just took my tranny apart today. I got it rebuilt back in May, last wek, I lost 3rd and 4th gear. Back to today, I found out that the locking ring that holds the 3/4 clutch backs had literally been blown out the back of the input drum. All but two of the teeth that hold the ring in were ripped out.

That got me and my tranny builder into the discussion of "how much is too much"? Basically, we figure I'm at that point where decreasing the line pressure will only have bad effects, and increasing it will also have bead effects.

In addition, 8 of the 9 Alto frictions were burned pretty good, but we don't know if that happened before or after the drum let go (had to drive it home 100 miles).

Oh yeah, my car's also a V6, for the record.

The transmission has the Superior Shift kit, Corvette Servo, and Alto Clutch pack, in addition to the Superior fix kits (got rid of the PWM TCC apply, etc.).

I put about 1100 miles a week (yes, that's one thousand one hundred miles a week) on my car , most of it freeway driving in the Bay Area at night. So, the tranny sees some serious use, between speed and shifting.

We figured this thing was relatively bullet proof without going major dollar on hard parts.

But, as my tranny builder said, every time he thinks he fixes one problem on these things, he finds another one.

Back to the main point, the Superior shift kit has a .471" boost valve, which is relatively small compared to some of the others (I've seen .500" and .521" boost valves available), so it's not like I'm running huge amounts of pressure.

 

When HPP3 says increase of 100% it means you are increasing ALL you can and without risk of damage.

 

"but most guys Ive talked to said a shift kit is a must if you have a stall."

False statement. Ask those guys why. The fact is, there are many people running high stalls without shift kits with no problem. Yank doesn't even recommend using a shift kit.

 

Is the "line pressure setting" you gentlemen are talking about in the PCM, the same as "Torque Management"? If it is I would like to know, for I am being told that when I swap my converter (Yank 3000) from stock, I will have to "delete" the TM setting in the PCM, on my 2001 Z28.

Thanks in advance.

SteveC

 

No, not the same as TQ management. TQ management has to do with reducing the ignition timing under certain circumstances (like during shifts.)

 

Max line pressure can be raised with Edit plain and simple. You can raise pressure at any and all throttle positions to whatever degree you want. This works much better than a shift kit and it can maintain much smoother shifts at low throttle inputs. There are multiple tables and when certain flags are removed you can get the pressure higher anywhere. As far as how high should you go? On a stock pump which is what most people use - even in built trannies - I normally shoot for about 220 at WOT. The tranny builder I use builds a special billet pump that is capable of 300 psi all day long without failure - so I run 275 in my car with a completely computer controlled transmission and spray through the shifts.

The high pressure is necessary due to the drum tolerances in the tranny. Extra pressure is needed to properly engage the drum properly under heavy loads. I have hundreds of hours seat testing actual tranny pressure with a very accurate mechanical guage in a fitting in the side of the tranny. You see the Tech 2 only gives you current readings which will correspond to certain actual pressure readings in psi. Figuring out those correlations allows you to then tune cars without a guage and only a Tech 2.

You could write a book on this very subject there is so much more but unfortunately I'm usually very busy at work

Chris

 

"Max line pressure can be raised with Edit plain and simple. You can raise pressure at any and all throttle positions to whatever degree you want."

Please tell us how to significantly increase line pressure with programming only for quicker firmer WOT shifts. Thanks.

 

Line Pressure 101 (Class is in section)

I will try to make this simple. The stock max line pressure for 4l60E or 700R4 is around 175 – 205 psi. The force motor controls the pressures. But the mechanical ability of the pressure valve assemble determines the max pressure. So, the force motor can increase line pressure at part throttle but it cannot increase the pressure above the mechanical ability of the pressure valve assembly.

The test for max pressure in reverse is not accurate. The fluid is routed in reverse through the reverse boost valve and the boost valve. The forward gears only apply the boost valve. The pressure valve is moved to determine pressure by way of two springs, reverse boost valve, and boost valve. The boost valve and the reverse boost valves will move and increase the spring pressure against the pressure valve, thus moving the valve to increase or decrease line pressure. So, if you have just the boost valve moving the spring versus the boost valve and reverse boost valve moving the spring, which one would give you a higher pressure? (Boost valve and reverse boost valve) The pressure in reverse will always be higher than pressure in forward gears.

SAFE LINE PRESSURE

The max line pressure on 700R4 is around 300 psi. It is hard on U-joints, rear ends, and tires. And yes, it is hard on the trans parts because there is more pressure on certain parts. I have seen the snap ring lugs bust on the 3-4 drums but it has usually due to a faulty drum, or the pressure valve sticking. I know that 300-psi. is a safe pressure for the 700R4 or 4L60E. I have seen many 700R4’s and 4L60E’s in the 260 – 300 psi range. There are certain measures that must be taken to ensure longevity of the pump at these elevated pressures. Once those measures are taken, then you can reap the benefits of running these high line pressures. The 3-4 clutch pack really needs these high pressures in order to ensure proper clamping force that is required by high hp applications.

Kevin Steele
Product Engineer
TCI Automotive

 

The positive pressure has an inverse relation to the base pressure table. You go to higher pressures by lowering PP and/or raising the BP. The right combination of adjusting these two tables in symphony will get you where you want. Adjusting the PP affects engagement pressure of the pump by throttle position and is of a constant nature. BP affects the pressure "spike" which occurs slighty before, during, and slightly after all shifts have occured.

When all the other constraints have been removed (there are 9 spots in Edit) then adjusting these 2 tables will give you all the flexibility you need to get it perfect. I have acheived 220 psi with the stock force motor with the right calibrations but only during the shifts. The stock pump cannot handle maintaining that kind of pressure engaged through every gear - it will give out in a fairly short time. It took me a lot of work to get this perfect but I've mastered Edit A4 calibrations like no other

Sorry it took me so long to respond but for some reason my server at work has chosen to lock me out of LS1.com and LS1 Tech

Chris