Transmission shift pressure

[timber74wolf]

I have a 2004 GMC Sierra with a 5.3. I was wondering if anyone has any idea what the standard line pressure for a stock 4L60E transmission with Vette servo installed would be; 1/2, 2/3, 3/4? I have the Superchips Flashpaq programmer and was going to increase the pressure, but I am not sure what would be safe and what is too much. I read on 1 of the forums about it, but I can not find it now. Any ideas of what it might be or what is too much will be greatly appreciated.

[GasGuzzler]

I'd like to help but the GM specs are PSC PWM vs. Line PSI....the chart is not split by gear changes. The GM chart just says how much the pressure should be for every PCS increment from 0 to 1.0 amp.

[timber74wolf]

Okay I know I am going to sound really silly with this, but could you break that down into Layman terms that I can understand? When I spoke to the Superchips Techy he said that they increase the line pressure up to 20 psi. So I am wondering if that is too much to a stock tranny?

[GasGuzzler]

You'd have to talk to someone familiar with tuning (not me).

The PCM controls line pressure with the PCS (pressure control solenoid) by using PWM (pulse width modulation = percentage of on time = rapidly turning the solenoid valve on and off at different rates). There are stock tables in the PCM that compare various factors (throttle position, engine load, vehicle speed, current gear, etc.) to determine the proper PWM percentage to control pressure.

[timber74wolf]

Okay Thanks! That explains a bit more to me. I appreciate it.

[ss454327]

Honestly I would find a good tuner and sell that superchip and have them tune everything for you. You could ruin a transmission fast by messing with shift pressures. You better have a trans cooler too or it's going to get really hot.

[farmtruc]

As long as the transmission isn't banging into gear, the line pressure isn't too high, generally speaking.
Some trucks shift firmer than others, so who's to say one line pressure is the standard, it just depends on what the GM guy felt like that day lol.

GasG is right, you'll never find out the true line pressure by playing with that handheld or file, you'll have to install a pressure gauge to get the exact line pressure, but then again, it's always changing.

Put the servo in and see how it feels.

later,
allen

[timber74wolf]

I installed the vette servo a while back and the shifting from 1st to 2nd was funky. Meaning it felt like a double shift. I pulled it all apart and double checked my instalation. Found nothing wrong with my instalation.
Anyhow as far as the Superchips go I got a Hell of a deal... to good to pass up and it is way better than my Hypertech. So for now it is fine.
I will be saving for a tune in the future though. Other bills come first.
Now I will say the Superchips did correct my shifting fom 1st to 2nd. I just used there 87 octane tune and the superchips value setup for the shift points and pressures, etc... And out of curiousity I called Superchips to see what the superchips values setup was. The techy said it increased the tranny line pressure up to 20 psi, top end speed limiter at 150, rev limiter at 6,200, etc... basically I was just wondering if the 20 psi was to much for a stock tranny with vette servo in it. I read something about the pressures in the tranny (4L60E) and someone saying to leave it at the stock settings... Anyhow to keep the story short I could not locate the thread so here I am asking questions to broaden my knowledge.
And I do have a trans cooler stock on the truck. I have the towing package.

[ma.racing]

sell your tuner and go see nelson or me i tune trany psi just by fill but your prob alot closer to nelson and well nelson is beta than me best tuner around other than jms and rwtd that i know

[ma.racing]

getin a good nelson tune will be your best bet or just do a 4l80e swap its well worth it