Vacuum mod ? No lock up .... HELP

[JOSH13]

I am having trouble trying to figure out why a friends car will not lock up .... His transmission was rebuilt not too long ago and the vacuum mod was installed on it and I am wondering if that is what is causing the issue. It ran just fine with the stock converter but after installing a brand new 2500 stall it will not lock up .... ? I have made all the changes that I have made to my stalled car and several others which I have tuned with no change .... When I command it with the vcm controls it will attempt to but just locks and unlocks continuously at lock up speeds .... Is there anything that needs to be done differently for a 4l60e with that modification ? Or what would possibly cause this ?
Any help / advice would be greatly appreciated !!
Thank

Josh

[ProTools4]

this is a commen mod on the LT1 4L60Es I commonly tune
if the TransGo VacMod 46-MOD is installed correctly the TCC will work

[JOSH13]

I'm not sure of what brand it is he just said he had them do the mod when he had the transmission rebuilt a few months back. So there isn't anything which should be tuned differently than a normal transmission with out the mod ? Line pressure etc . . . . Because I've tried several things and just can't make it lock and remain locked

[jimmyblue]

You should look at TCC_Mode to see what it "thinks" it's
doing, and TCC_Slip_RPM for what results.

A vacuum modulated trans isn't necessarily going to be
free of the issue that a small converter needs more line
pressure to hold, and the line may be starved at low
pedal (depending on how the vac mod is set up). Then
you have your TCC min duty and "slip learning" that can
further reduce your delivered pressure to the converter
clutch. I'd put min duty to 98% if you are seeing a soft
slip and no TCC_Mode = --3-- in the table display.

TCC_Mode = --3-- means misfires are inhibiting lockup,
this is a hard cycling kind of slip.