Max line pressure

[Cheatin_Chad]

There is a field in the transmission tab that has "90" as max line pressure.

This can't be the line pressure in PSI can it? I was told it was 170 in drive.

Can someone give me some information on adjusting line pressure for a 98 F-Body ?

[mustbbrent]

CC, are speaking of scanning or info on the tables?

on the table values, my understanding is the lower the number, the closer to maximum line pressure used.

For instance, on my 03 truck, with Edit, most numbers are in the 500 range, but over 90% and close to 100% TPS, they are as low as 20 and it definitely hits a ton harder at shift.

[Casey]

There is a field in the transmission tab that has "90" as max line pressure.

This can't be the line pressure in PSI can it? I was told it was 170 in drive.

Can someone give me some information on adjusting line pressure for a 98 F-Body ?

It's an adjustment range.

Even if you tell the VCM to call for zero line pressure, it does not go to zero pressure on the trans. With the PWM solenoid bleeding off all of the pressure there will still be a line pressure anywhere from 55 to 75 PSI.

You have to go by the force motor current to get the actual line pressure. In the factory manual there will be a table that spells out what current/line pressure should be for that model. Verify with a line pressure gauge on the trans.


Ken

[mustbbrent]

Ken, in that line pressure is it like LS1Edit where the closer to 0 you get, the more line pressure there is applied?

Sorry, I shouldn't have answered. :-X I am still waiting on your kit. I hope it to be here Monday... ;D Just going off past experience from Edit.

[Casey]

Ken, in that line pressure is it like LS1Edit where the closer to 0 you get, the more line pressure there is applied?

Sorry, I shouldn't have answered. :-X I am still waiting on your kit. I hope it to be here Monday... ;D Just going off past experience from Edit.

You are thinking of two different tables. On the shift pressures and max line pressure, the higher the number the higher the commanded line pressure will be.

Now if you take the number from the Base Shift Pressure Vs Torque Vs Gear tables, that is your commanded line pressure and it is compared against the Max Line Pressure value.

If you exceed that value, the max line pressure will be used.

Now take the number you have from those tables(it will be from 0-96), it will be used on the Force Motor Current Vs Commanded Line Pressure Vs Temp table.

The Force Motor Current Vs Commanded Line Pressure Vs Temp is the calibration table for the transmission pressure solenoid. The higher the number on this table (more current) the LOWER the trans pressure will be as the solenoid is bleeding off line pressure through a relief valve.


Unless you have a very good reason to to recalibrate your solenoid curve, don't mess with this table . We only put it there because some people have thrown that table out of whack thinking is was Pressure VS TPS. It's not.

If you do plan on recalibrating the solenoid pressure curve, please do so by verifying the trans pressure and current required from that table to achieve it. There is a whole section in the factory manual dedicated to this procedure.

Othewise you will wind up with blown trans seals and crushed friction plates.

We put all of this in the help section. So please read it. If you are unsure, work with your trans builder.


Happy tuning

Ken

[mustbbrent]

Ken, Any chance you have a copy of what that table should look like at or near stock? Of course my tranny is built. I am looking at that table and it starts at 1094 on the top left and goes to 20 at 96 commanded line pressure and then at 100 commanded line pressure it jumps back to 1245. Can that really be correct? Or am I going to blow a gasket with this kind of table?

It's an adjustment range.

Even if you tell the VCM to call for zero line pressure, it does not go to zero pressure on the trans. With the PWM solenoid bleeding off all of the pressure there will still be a line pressure anywhere from 55 to 75 PSI.

You have to go by the force motor current to get the actual line pressure. In the factory manual there will be a table that spells out what current/line pressure should be for that model. Verify with a line pressure gauge on the trans.


Ken

[mustbbrent]

One other question. On the Brake: Shift Pressure vs. Torque vs. Gear, am I miss understanding the table or should the left side, be 2->1 not 1->2, then 3->2, not 2->3, and finally, 4->3, not 3->4.

the table is all 0 -ed out, just trying to understand what the table is all about. Thanks.

[guardsman01]

I wass looking at the Force Motor CurrentvsPressurevsTemp,
and the values there look to correspond with what you would see as a current value to the Force Motor (I know, clear as mud).

Explained, the PCM uses a variable current of between 0 and 1.1 amps. 0 Amps is no prssure bleed off, hence, max line pressure (this is so if the trans loses power, it will automatically go to max line pressure).

Now, I'm not sure how GM did it, but the Force Motor Current/Line Pressure Values are different between the V8 and V6 F-Bodies, but they use the same Force Motor (Solenoid).

Anyhow, the values of 1094 (1.1 Amps at Min Line pressure) through 92 (about .09 Amps at Max Line pressure) make sense when you compare them to the current values.

Hope that helps.