Vibration in VDJ AB60 after Auto Conversion

TABLE OF CONTENTS

• I am experiencing a Vibration in my vehicle at low RPMs after the auto conversion
• Shuddering must be due to the transmission slipping!
• The Torque Converter or Flex Plate is Unbalanced!
• It didn't do that when it was a manual!

I am experiencing a Vibration in my vehicle at low RPMs after the auto conversion

If you experience a vibration at low engine RPMs (1400 - 1600rpm) then the most common issue we have seen cause this is related to the engine tune. Be it a piggy back ECU such as ARMAX/UniChip or an Engine Flash Tune/Remap, this issue is most common when coupled with larger injectors.

We have been told by a well-know and reputable engine tuning specialist, this is a result of injector scaling, causing the wrong amount of fuel to be fed into the cylinder giving an effect of a miss-firing cylinder.

It happens around the 20-25% throttle input and is most prominant when in 6th gear and the Torque Converter is locked, creating just the right amount of load on the engine at light throttle. It does happen with the Torque Converter unlocked but the fluid coupling in the torque converter is able to absorb the vibration enough that you can not feel it in the cabin. However we have datalogs that show it is still present.

When we first discovered this issue, we replaced everything in the conversion and made zero change the intensity or prevalance of this vibration. However, by pure accident, we found that if you lifted the air intake on the air filter box and drove in that configuration, we were able to stop the vibration. We wouldn't recommend this, but it was our proof that it wasn't related to the automatic transmission.

The vibration is similar to that of the vibration you experience if you tried to accelerate in a Manual gearbox vehicle in 5th Gear at 20km/h. It vibrates because it's too much load at low rpms.

You can see here in the data log showing the vibration happening with the Torque Converter Locked.

And again with the Torque Converter Unlocked. It's amplitude in lower but still present.

Shuddering must be due to the transmission slipping!

While yes, you are correct that a slipping transmission will create a shudder. It is also more likely for the slipping to happen at heavier throttle, not light throttle. More Engine Torque = More Slipping.

Also, a slipping transmission would also result in an "Incorrect Gear x" DTC or a "P2757 - Torque Converter Stuck Off"  DTC logged in the COMPUSHIFT system which would trigger the COMPUSHIFT Failsafe Mode. If you are not seeing any DTC errors or Failsafe modes, then the transmission is not slipping.

The Torque Converter or Flex Plate is Unbalanced!

Again, yes the Torque Converter and Flex Plate, IF unbalanced, would create a vibration. However that vibration would not happen at a specific throttle opening. It would happen at any engine RPM irrespective of throttle input or load. And it would happen through out the RPM range, not just at a specific RPM.

It didn't do that when it was a manual!

We will often mistake this vibration as the indication that we are in too higher gear for the speed/acceleration we need, and will downshift to a lower gear. The auto allows you to contine powering through the RPM range using the torque converter for what it was designed for.

If you would like to discuss the matter further, please contact our tech support team via email at techsupport@askorto.com.au or call 03 9762 8004 opt 2.