VZ Holden poor Trans shifts

[rally1]

Hi all, we have had a few auto VZ Holden’s of late that no matter what we do we cant get a firm and fast 1-2 shift under full load, we have done all the things we can think of like upping the line pressure removing all TM lowering the amps to 0 in the bottom 2 lines of the force motor current, drop the shift times to .1 and turn off learn trims in power mode. logged data shows throttle staying at 100%, line pressure control solenoid and 0 amps and no TM, we get a very firm and positive shift below half throttle but very very slow and soft above that, on all older model Holden’s (VT-VY) its very easy to get a good firm shift so is there a difference in the shift routines on the later model 1mb computers?
Has any one got an answer to fixing this or run into this with Holden’s?

We where looking into a new servo and maybe a few other things like replacing the accumulator spring and drilling out the valve body plate has any one had good results with these mods??

[shane]

Have had the same trouble myself, may be in the trans itself as the 2-3 seems ok and3-4 is ok but no matter what ive done 1-2 is crapp at full throttle.Only on vz as well .Any one else had this?

[OLS108]

Have had the same trouble myself, may be in the trans itself as the 2-3 seems ok and3-4 is ok but no matter what ive done 1-2 is crapp at full throttle.Only on vz as well .Any one else had this?

Yep, had the same on a mates VZ as well. i couldnt work it out either.
problem with the Software ??

[shane]

Seems to be more in the trans itself i reckon, any tranny guys come across this?feels like the line pressure is slow to come in or something like that.When you wind up all the pressures in the software it makes a harsh shift at part throttle but still ordinary at full throttle.

[joecar]

Try this:

Set both D1206 and D1207 to 100% (disabling the trans WOT mode)...
then make sure all your PT shift tables have suitable values in their upper range.

The idea behind this is that if shift quality is good at PT, then let the PCM think it is doing PT shifts instead of WOT shifts.

Let me know how it goes.

Cheers
Joe

[rally1]

Ahhh that makes very good sense Jocar, we have one in the workshop tomorrow so will give that a shot and let you know what happens Do you know what the dereference is in the way that the shift varies between PT and WOT? Does it slow the speed and which one clutch/band is released and the other is applied?

[shane]

Thanks Joe will try it on next VZ will let you know.

[joecar]

I think it does this:

WOT mode: it spikes the pressure to some high value and uses the WOT MPH and WOT RPM shift parameters.

PT mode: it uses the shift pressure/adjust/time tables, adaptive learned pressure, and the PT shift MPH tables.

There maybe other differences... but just be sure to bump up the pressure tables.

Cheers

[rally1]

Hi guys, tried the set up that Joecar mentioned and no luck unfortunately, looked at the shift times and at light throttle we have a shift time of .3sec but not matter what we do WOT shift times are around .7sec

We will try and make a few mechanical changes to the Trans but from memory the VZ already has a small servo piston for the band so will have to look at the accumulator side of things (which from memory might not even have a spring!!!) and maybe the valve body plate holes, has anybody done these changes on a VZ???

Times like this a really wish GM had a pressure test port for the band servo

[OLS108]

Hi guys, tried the set up that Joecar mentioned and no luck unfortunately, looked at the shift times and at light throttle we have a shift time of .3sec but not matter what we do WOT shift times are around .7sec

We will try and make a few mechanical changes to the Trans but from memory the VZ already has a small servo piston for the band so will have to look at the accumulator side of things (which from memory might not even have a spring!!!) and maybe the valve body plate holes, has anybody done these changes on a VZ???

Times like this a really wish GM had a pressure test port for the band servo

There must be another way to do it via the software ?? Ive been in VZ LS1's that shift nice and hard. Anyone ?