Tuning for Transmission Pressure
ramairws6 - We're just trying to help based on our own experiences; both good and bad. At your power level you may want to consider a TH350 or TH400 or putting the car on a diet. As you stated incompetent tuning can destroy a PCM controlled 4L60E. That is usually caused by people incorrectly adjusting or experimenting with line pressure. Frank at Perfomabuilt does prefer PCM controlled, but I'm pretty sure he also recommends leaving the line pressure tables alone. I would call him for some advice.
In regards to your original post; what are you trying accomplish by adjusting the line pressure?
In regards to your original post; what are you trying accomplish by adjusting the line pressure?
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
The PCM controls line pressure indirectly via torque signal pressure which it calculates based on load... i.e. the PCM is doing what a vac mod is doing...
There are several key points:
- the transmission requires internal parts that support zero slippage when adequate line pressure is applied (i.e. suitable clutches, bands, servo pistons, built with suitable clutch clearances...);
- the PCM or the vacuum modulator must ensure that adequate line pressure is applied during critical events (i.e. during shifts, during high load);
- with the 4L60E/4L80E you should minimize the shift times... during shift transitions the releasing component is "slipping down" and the applying component is "slipping up"... by minimizing the shift time you minimize this transition slip (this is what shift kits did before computers came along)... this should also supported by increasing pressure during shifts; on the 4L60E/4L80E the hydraulic circuit that is applying the component for the next gear is also releasing the component for the previous gear (i.e. fluid pressure that applies the 3/4 clutch also releases the 2nd band)... this is not true of the 6L80/6L90 (which use mutually exclusive hydraulic circuits for each component), so trying to minimize shift times on the 6L80/6L90 may cause binding (destroys clutches by forcing them to slip, and breaks hard parts).
slip is bad, this is what primarily kills a transmissions... slips burns the friction material from the clutches/bands, which in turn promotes more slip... slip heats and burns the fluid which causes it to lose its properties which may also promote more slip.
My $0.02.
There are several key points:
- the transmission requires internal parts that support zero slippage when adequate line pressure is applied (i.e. suitable clutches, bands, servo pistons, built with suitable clutch clearances...);
- the PCM or the vacuum modulator must ensure that adequate line pressure is applied during critical events (i.e. during shifts, during high load);
- with the 4L60E/4L80E you should minimize the shift times... during shift transitions the releasing component is "slipping down" and the applying component is "slipping up"... by minimizing the shift time you minimize this transition slip (this is what shift kits did before computers came along)... this should also supported by increasing pressure during shifts; on the 4L60E/4L80E the hydraulic circuit that is applying the component for the next gear is also releasing the component for the previous gear (i.e. fluid pressure that applies the 3/4 clutch also releases the 2nd band)... this is not true of the 6L80/6L90 (which use mutually exclusive hydraulic circuits for each component), so trying to minimize shift times on the 6L80/6L90 may cause binding (destroys clutches by forcing them to slip, and breaks hard parts).
slip is bad, this is what primarily kills a transmissions... slips burns the friction material from the clutches/bands, which in turn promotes more slip... slip heats and burns the fluid which causes it to lose its properties which may also promote more slip.
My $0.02.
Thread Starter
Joined: Sep 2004
Posts: 2,013
Likes: 85
From: Hicksville MN!
Thread Starter
Joined: Sep 2004
Posts: 2,013
Likes: 85
From: Hicksville MN!
Allrighty then lets hear your input. Other then saying you should get this so and so trans from this so and so vendor cause of hearsay isn't knowing too much to me. If I remember right you were also braging up the bulletproof Rock-On trans you once had?? How about the awesome Fuddle vertor you owned?? Where do these 2 sponsors products rate for ya today!? Anyone can brag someones product up on hearsay but do you know why its good or bad or what makes it good or bad?? I am one to learn and find out how things work and what makes things work right or wrong. I posed the question to learn how things work and not saying I'm right or wrong or to get into a pissing match. But it seems your trying to turn it into that!!?? If you have some good input on how the internal trans pressure makes 3-4 clutches survive...................well then I'm all ears.
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Verdad Gallardo Allrighty then lets hear your input. Other then saying you should get this so and so trans from this so and so vendor cause of hearsay isn't knowing too much to me. If I remember right you were also braging up the bulletproof Rock-On trans you once had?? How about the awesome Fuddle vertor you owned?? Where do these 2 sponsors products rate for ya today!? Anyone can brag someones product up on hearsay but do you know why its good or bad or what makes it good or bad?? I am one to learn and find out how things work and what makes things work right or wrong. I posed the question to learn how things work and not saying I'm right or wrong or to get into a pissing match. But it seems your trying to turn it into that!!?? If you have some good input on how the internal trans pressure makes 3-4 clutches survive...................well then I'm all ears.
Sounds like you all ready have your mind made up and the coarse you want to take. Now that you have efilive, change all the **** you want.
I dont believe I ever bragged about my rock on trans, I didnt have time to. Me along with alot of other poeple got burned on here because of their shotty business.
My fuddle converter has been doing well actually, I still run it! So, you dont know WTF you are talking about. Anything else you want to point out?
Your good on finding old threads, search FLT and dig some up, there reputation speaks for itself.
Last edited by waterbug1999; Jun 23, 2009 at 12:01 AM.
Ramairws6 real race cars have three pedals, put a 6 speed in it and you will be done. Look at the benefits of the six speed better gas mileage. 
Thread Starter
Joined: Sep 2004
Posts: 2,013
Likes: 85
From: Hicksville MN!
You can try to lower the shift point, or raise the rev limiter (or maybe both) to widen the gap so the trans has a little more time to shift..
Or, you can see if lowering the shift times (to make it shift faster) helps and/or see if raiseing the pressure helps.
Last edited by waterbug1999; Jun 24, 2009 at 05:24 PM.
i have to find someone to tune it or i need a new pcm because this was tuned for the cam an all other uprades but i think the guy fucked me its cool car runs like crap ran better before the tune i think a tune won't help but its costing me top dollars.
that's why i want a 6 speed or i'm going vaccum modulated.
that's why i want a 6 speed or i'm going vaccum modulated.
Either pay money to get your own tuning software and learn how to use it, or pay to have your car tuned by a pro.
Changing PCM's wont solve a thing and going vaccum mod doesnt mean that it help your rev limite problem. You need to open up the window to give it more time to shift.
Changing PCM's wont solve a thing and going vaccum mod doesnt mean that it help your rev limite problem. You need to open up the window to give it more time to shift.
This guy in Kenner,La changed the tune for me an the car ran like crap after he done that but it shift to 2nd soon as i hit the gas i hate my car fellas my 98 ss never gave me trouble. i think i'll go with a 6speed