VT Transmission issues

[olddudes]

Having a few issues with my VT auto changing through the gears, on takeoff the gearbox is in 3rd gear up to about 20km/h then it will try to change down to 2nd or 1st gear, there is also a loss of power in these gears and some minor shuddering. 40-50km/h receives some heavy shuddering as its trying to shift gears, once over this speed and it hits 3rd gear the car runs beautifully. I've tried resetting the computer. I've tested the error msgs, and i receive 12 and 92 but neither of those seem to be related. The trans fluid level is also fine.

Any suggestions other than a new gearbox?

[danja]

What is the condition of the fluid like?

Could also be an electrical fault. Any other signs that the battery/alternator might be failing? Damage to any wiring looms?

[olddudes]

The fluid is fine, battery was replaced last week and the alternator is fine. It seems like the geabox is still changing gears correctly, but it doesn't know which gear it wants to be in. Does this mean it could be a problem with my PCM or TCU?

[danja]

Potentially it could be an engine management issue, or something mechanical in the box.

Often transmission problems are solved with a fluid change or top-up, but by the sounds of it your is in good condition. You might want to check the speed sensor isn't loose or damaged, though you'd expect a trouble code for that.

If that doesn't help I'd be talking looking at a new box or a rebuild.