VY II Commodore 4-3-4 shift in cruise control

[Mick1988]

Hi all,

Just upgraded from a 2002 VX II Commodore to a 2004 VY II Commodore and overall I'm impressed. I even went from a Berlina to an optioned out Executive (ex police) and haven't felt ripped off in terms of comfort and features. Both are Ecotec V6 autos the only difference is the VY runs the twin cats like a VZ.

However I use my car regularly for towing along the Forest Highway in South-West Western Australia. It is a mostly flat highway with only a few hills. My VX used to tow a loaded car trailer with a car on the back doing 105km/h in cruise control and would only ever drop back to 3rd a few times at those large hills. Even last night towing a caged 6x4 trailer with 14 tyres in it I had a bit of downshifting I deemed unnecessary.

However I've noticed the VY does quite a bit of unnecessary downshifting when only on a very small incline and sometimes I could almost swear it's downshifting on the flat. This obviously uses more fuel and gets pretty annoying to hear and also can't be good for the gearbox.

So just wondering if there is an adjustment I could make with the Tech 2 (I don't think there is) or something simple I could change / do to increase the torque of the car. I do like the car but I don't want to run into gearbox issues down the track and I also don't like using an extra 1-2 liters per 100km doing the same trip I always did before.

For what it's worth I had the VX Berlina from 126,000km and it now has 175,000km and I got the VY wagon at 119,000km now with 123,000km on the clock. Any thoughts or input would be great. Almost considering a super 6 conversion lol

 

[wagon_vs]

I have always heard when towing heavy loads just to leave the trans in 3rd, but I can't remember the reasons behind it.

Sent from my XT925 using Tapatalk 4 Beta

 

[Futech]

There's heaps of companys out there that can flash your PCM to change shift points and also make it a bit more sport like on the shift. Mace Engineering is one of them.

 

[Futech]

Just to add, i tow a boat with mine when it had the 3.8 in it and didnt have any issues.

 

[Mick1988]

Might go check tyre pressures etc but it seems the motor just lacks a bit or torque or else the shift points need to be recalibrated as said above.

If only VYs had tip tronic

 

[chargedvx6]

Vy runs a different trans calibration. Have a look at the puny 13mm thickness of the Vy radiator (compared to VX at 40mm odd) and most likely it also won't have an external trans cooler. The combination of drastically reduced trans cooling ability of the system and the associated tune to go with this results in what you feel.

I would not alter the tune until you've improved the physical cooling ability of the system. A large pwr trans cooler will work wonders. A lot of the transmissions actions are played off on road speed vs throttle input vs trans temp. If the temp is over a certain level the tune will always take the easy option of unlocking the torque converter clutch and kicking it to 3rd.

 

[Futech]

As above. If your doing a lot of towing you sound have external trans cooler. That goes for any vehicle.

 

[Brett_jjj]

Does it do it in both power and economy modes?

 

[Nathern]

If you want to fiddle yourself you can go here pcmhacking.net - View topic - FS: USB Communications Boards and
1 Buy the usb connector
2 download the flashtool from the same site
3 Suck the PCM program out
3 Modify the program with TunerPro (free)
4 Reload program into PCM
Thats what I did, Although I do recommend having a good look around the forum first You can also use it to diagnose faults by looking at the real time sensors ect.