TCC apply solenoid PWM control....

[guardsman01]

Are you guys working on adding control of the TCC apply solenoid PWM duty cycle?

I know you guys have a whole lot on your plates, but that's one thing that I'm really waiting for.

I'm chewing up my torque converter clutch because of GM's f***ed up TCC apply strategy (no fault of HP Tuners).

I have been using another scanner to watch my transmission, specifically my TCC Apply Solenoid PWM Duty Cycle.

When cruising, the PCM commands around 100% duty cycle, but if you slightly increase the throttle, i.e. to make a small speed increase, the PCM starts backing off the duty cycle, and allows the TCC to slip.

I'm assuming GM did this to decrease vibrations transmitted to the car, lugging the engine, etc., but I find it annoying as h***.

I have the PWM apply defeated mechanically, but with the TCC that I'm using, the pressure still drops enough to allow it to slip, and that's chewing up the TCC.

So, what I'm looking for is being able to get rid of the variable PWM duty cycles, and just make them all like 98% (so it doesn't overheat the solenoid) as long as the TCC is applied.

That would make effectively make it "On-Off" TCC.

Many thanks guys.

[jimmyblue]

There are two tables, base and offset, which give
you some control over that; I forget which way they
go but you can increase or decrease the value that
the PCM swings the pulse width, by. I'm pretty sure
there is a thread about this in the V-8 Transmission
section though it was maybe 3-4 releases back.

However to get my TCC to hold (TCI SF3000) I also
had to play with the force motor table a lot, and
"hold" is a matter of degree... the TCC gets a
knockdown of a knockdown of the mechanical line
pressure.

[guardsman01]

My car's a V6, so I don't have any control other than the force motor tables right now.

Something is screwy in my tranny right now, and the pressure is fluctuating around, so I don't want to go cranking the line pressure up. I think it might be the force motor itself, I installed an aftermarket one, and it has been acting strange since then.

So, I'm just waiting to be able to control TCC solenoid itself.....

Also, the TCC apply signal itself is actually capable of going to full line pressure.

There are two solenoids with pistons to control TCC Apply,
1) the TCC PWM Solenoid (this is in the valve body), this controls the apply pressure going to the TCC, and
2) the TCC Apply Solenoid (this is in the pump body), which actually opens and closes the TCC Apply signal

The TCC Apply Solenoid just acts as a valve, and allows the TCC to engage.
The TCC PWM Solenoid controls the actual apply pressure.
It provides a gradual pressure increase when the TCC engages, so that it doesn't jolt the car for average joe.
It also varies the pressure while engaged, to allow the TCC to slip at varying rates. The only reason I can see why GM would do this is to dampen vibrations transmitted from the engine to the rest of the car, again, to keep average joe happy.

Basically, this works fine for somebody who doesn't care about how their car works, and doesn't plan on keeping it for more than a few years. They'll get rid of it before the tranny chews itself up.

But, for people like us, it just gives us a time bomb waiting to go off, and have to repair every couple of years.

[Tobin]

On a 97 Buick Lesabre, I increased the PWM pressure to the TCC by installing a 1 watt, 100 ohm resister between the PWM circuit and Ground.
This pre-loads about 1.7 volts on the PWM solenoid which permits the PWM to operate as designed but increases overall average pressure to the TC.