CoonToot

...in any way OTHER than through the EPC solenoid? My local tranny shop just installed a TransGo vac mod kit, yet the tranny is slipping on every upshift. My feeling is that the guy may not have installed the vac mod kit correctly as slipping in all gears probably points to low line pressure across the board. I just need to know if the EPC solenoid, which is bypassed/pacified with the vac mod kit, is the only point of line pressure control via the PCM. In other words, if the EPC is removed from the equation, is there any other manner by which the PCM could control/effect line pressure?

12sec.5.3

iTrader: (1)

No, I believe once you bypass the solenoid with the vac mod kit, the only thing that controls your shift pressure is the vacuum from the engine. Make sure the connections are tight on the brake boost hose and where it connects to the tranny.

goshawk23

do like 12sec.5.3 said. if you have a leak somewhere, you will have that problem.

gonzo 6.2

iTrader: (8)

See,amature responses with no clue.
A trans with a modutator that has no vacuum will shift very late and really hard.Your problem is somewhere in the install.

TeamTripp

Line pressure does not change shift points in a 4L60E, they are done via a pair of shift solenoids still controlled by the PCM.




Did you do the vacuum modulator trying to fix the slipping concern, or is this what happened after the install?

gonzo 6.2

iTrader: (8)

Didnt say it did.

So are you saying a 4L60E with a modulator kit installed will act different than a THM 350/400 running with the vacuum line off?

What will a vaccum controlled 4L60E do if the line is not connected to a vac. source?

TeamTripp

You said "a trans with a modulator that has no vacuum will shift very late and really hard."

Since the topic at hand was a 4L60E converted to use a vacuum modulator, I assumed thats what you were talking about. A modulated 4L60E will act different than a THM350. A THM350 uses modulator -vs- governer pressure to control shift points, 4L60Es are still done electronically via shift solenoids. Removing the EPC in favor of a modulator does not change the shift solenoids so they are still controlled by the PCM. So in a 4L60E, removing the vacuum line will only make it shift hard (max line pressure), but the PCM will still command stock shift points.

gonzo 6.2

iTrader: (8)

OK thanks for the education. What do you think his problem could be?

TeamTripp

I try to help out when I can.

I have a few ideas as to what could be wrong, but I'm waiting for a reply to my question I posted earlier:

"Did you do the vacuum modulator trying to fix the slipping concern, or is this what happened after the install?"

12sec.5.3

iTrader: (1)

Excuse me for being an amature, ASSWIPE! I'll be sure to get your opinion before I try and help anyone again.