Llws_2004

Hey guys I have a 2004 gto. It originally had the t-56 in it and I swapped in a 4l60e that is being controlled by a tci ez tcu. When I first got the swap done the shifts were very harsh. I just installed a new valve body yesterday and that made the shifts back to normal. My next problem is that when I go from park to either reverse or drive the engagement is extremely harsh. To the point where the rear of the car squats about an inch and feels like something in the drivetrain is going to break. Once it's in drive the shifts are fine. Anybody have any ideas?

mrvedit

You need to hook up a trans pressure gauge to see what the line pressure is at idle, drive, etc. Lookup "atd 5550" on Amazon, it is only $34.

I'm surprised that replacing the VB calmed the shift down. Please detail exactly what you replaced, e.g. VB, separator plate, which solenoids if any, etc. Did you replace anything in the 1-2 accumulator?

Off the bat, I think your TCU is commanding max line pressure at idle. The pressure gauge will also let you see the commanded line pressure when you accelerate, etc.

Llws_2004

It was a rebuilt valve body that came with all new solenoids. And I got a transgo separator plate. I didn't replace anything in the 1-2 accumulator. I didn't even take it apart to look at springs and piston.

So next thing to check is line pressure?

mrvedit

Yes, I think you will find the line pressure sky high.
I suspect someone had drilled the separator plate too aggressively and the replacement toned it down, or the Pressure Control Solenoid (PCS or EPS) was defective.

Llws_2004

I will check line pressure and report back. If it is very high what are the possible causes of that?

mrvedit

High line pressure can be caused by the PCM/TCU commanding it, a defective PCS or a stuck/defective/wrong boost valve.
The pressure gauge comes with a long hose so that you hang it from our outside mirror and read it while driving. I think you will find it informative and useful.

Llws_2004

so i finally got around to checking line pressure and at idle it is 155psi, drive is about 180 and reverse was 205. How do those numbers look?

mrvedit

Sky high at idle, as I expected!
Stock idle is around 55-65psi; with a big boost valve about 65-75psi.
I've seen 85psi with a cold tran, but dropping to 75psi as it warms up.

I would replace the PCS (Pressure Control Solenoid); it is either defective or someone fiddled with it.

Llws_2004

The pressure solenoid can be replaced with just dropping the pan correct? I will get a new solenoid tomorrow and give it a shot and report back. Thanks for the help so far.

mrvedit

Yes. Generally you also have to remove the 1-2 accumulator - the dome shaped thing with 3 10mm bolts. You might as well check the accumulator - make sure the springs and piston are not cracked or broken.

If your pan doesn't have a drain, use a simple hand pump to pump the trans fluid out through the dipstick tube. Like this:
http://www.harborfreight.com/multi-u...ump-66418.html

Otherwise it makes a big mess because the fluid more than fills the pan.