This weekend, I did an "Ultimate pan drop mod" kit for a coworker on his '03 Tahoe.

Parts/ mods list is as follows:

-Sonnax .490" boost valve
-Transgo pressure regulator valve
-Sonnax o-ringed end plugs
-Sonnax forward and reverse abuse valves
-Central Valvebodies AFL valve (with the purple/yellow 3-2 spring inside)
-new shift solenoids
-blocked the 3-2 shift valves
-eliminated the 4th accumulator
-Cranked the EPC solenoid adjustment screw 1/4 turn
-New spacer plate, drilled as so*:


The pressure in OD when revved up is about 280 psi, and in reverse, it pegs the gauge at 300 psi (as high as the gauge goes).

The guy is pleased as punch with it, and he drove it to work today, I'm just wondering if this is normal, and if it will cause any problems in the foreseeable future.

Full story: He was complaining about a 2-3 shift flare, so I recommended the mods. It turns out he had been running it really low on fluid; it couldn't even make minimum line pressure when I checked it, and the needle on the gauge was bouncing around. I told him I'd do the job, with no guarantee. He agreed. There were no excessive metal shavings in the pan, but some clutch material, so I agreed to do the job (I told him I'd refuse if the pan was full of metal). The fluid wasn't good, but not black, either.

*Those are the same hole sizes I used on my build.

For those of you wondering, I finished my build, but haven't installed it yet. I'm expecting good results.

EDIT: I forgot to mention that I vacuum tested the valve body, and it SUUUUCKED before, and every thing was good/ excellent after.
I'll post the pertinent numbers if you want, but just take my word that everything was good.

 

Those pressures seem high to me. Were the idle pressures high also? I would try turning the EPC back a1/4 turn and see if the pressures come down some. I have never got over 230/240 psi on any of my builds with basically the same mods. As for longevity, I would think that there would be higher pump wear and possibly blow the 3-4 clutch snap ring out of the drum.

I will say though that I have never ran a trans with pressures that high so take what I say with a grain of salt.

 

i went through a '96 60e valve body for my caprice last week. the o-ring end plugs (yet again) made a big difference.

i thought playing with the epc adjustment was only a last ditch effort to raise pressures?
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you increased the regulator stack in 5 different ways. There should be no reason for surprise that the pressure is way high.
The worst offence will be listed first, the rest is good practice

-turned the EPC screw
-boost valve with larger ratio
-firmer spring in the PR lineup
-new AFL valve to correct leaks (which will increase AFL pressure)
-additional spring pressure inside the AFL lineup (which will increase AFL pressure on top of the new leak free valve)

Messing with the EPC screw is a big no-no in my book.
I'd turn that thing back and see where it's at. Proper AFL, with added spring, with the LB1 booster...you're likely looking at 240psi in OD if the pump is healthy

 

@MaroonMonsterLS1 what would be an example where you would turn the screw on the EPC solenoid? And if its not supposed to be adjusted what is the purpose of the adjustment screw?

Simply for conversation purposes here.......

 

Idle pressure was 70 in P/N/OD, and 100 in reverse.

 

Please post the before and after vac numbers. I'm trying to learn more about the 4L60E and it would be nice to know what the more common replacement parts are for the VB and how they are addressed. I realize that it's largely based on how the initial vac readings look for the various circuits, but actual before and after findings are always of interest. What was your approach? Did you simply use the 4L60E vac test guide and address with the recommended Sonnax part for circuits that were too low, or was some Trango parts involved? I know the different reamers from Sonanx can be expensive, so I'm assuming cheaper Transgo substitutes (where applicable) are sometimes used for the repairs?

I'm assuming this valve body has some areas where new parts are always used regardless of how the vac readings look? (outside of the parts replaced that are used to optimize shift characteristics)

 

short answer never
purpose is for factory calibration
it changes the "closed" position of the valve and shuts off exhaust for tq signal

p.s. a 1/4 turn is an absolutely HUGE amount of adjustment.

 

Then is there any way to verify that I've adjusted it back to the correct position?
Like an ohm specification?

 

No
You're altering the physical preload and travel on the valve itself contained in the epc
now you either get to replace it, or play guess and check

 

Well, ****. I was afraid you were going to say that.

Quarter turn back it is.
I'll check back with the new pressures in a few days.

The funny thing is it shifted really well; not harsh at all .

 

Okay, boys, I dropped the pan tonight and backed the EPC screw off exactly 1/4 turn.
I nailed it (this is at 5K RPM in OD, standing on the brakes):




For the record, pressures at idle in P/R/N/OD were all the same as before; I guess that is the better valves at play.
Pressure in reverse while revved up still pegged the gauge, but from what I've read, reverse pressures normally go over 300 psi, and how often are you flooring the gas in reverse?