Non linear shifting, slight jerking 2001 Volvo S80 T6

[vegasjetskier]

This effect was probably due to the traction control. When you punch it a lot of torque is applied to the front wheels and they might break loose. The traction control then comes on to limit wheelspin and makes the car feel like it's surging. Don't worry about it, you're accelerating as fast as you can for the conditions.

[vegasjetskier]

So, it may not be the ETM issue that seems to be prevalent in the 2000 + S80's?

Well if it's only occurring at or near wide-open throttle, I'd say it's the traction control. If it occurs at less throttle, it's probably the ETM. The T6s make a lot of torque, more than enough to overcome the traction of the tires. So, it's easy to activate the traction control @ wide-open throttle.

[JRL]

So, it may not be the ETM issue that seems to be prevalent in the 2000 + S80's?

Well if it's only occurring at or near wide-open throttle, I'd say it's the traction control. If it occurs at less throttle, it's probably the ETM. The T6s make a lot of torque, more than enough to overcome the traction of the tires. So, it's easy to activate the traction control @ wide-open throttle.

It is not the traction control if this happens over 35 mph, the control is absent after that.
T6's have a history of VERY BAD transmissions and tranny failures but it's very hard to tell your syptoms by the way you describe this...
try again

[JRL]

From a standing full throttle yes, the traction control will kick in, but if it does this from say a 35 MPH kickdown then it's someting else. This should stop at 35-40 mph
Can't you shut off your traction control?
If so do it and see if this still happens

[vegasjetskier]

From the S80 Owner's Manual:

Stability Traction Control (STC)

The STC system is designed to help reduce wheel spin by limiting power to the drive wheels if they begin to lose traction. At speeds over 25 mph (40 km/h), the STC system monitors and compares all four wheels. If one of the drive (front) wheels shows any tendency to slip, such as when driving on slippery roads, the difference in speed is immediately detected. This triggers a signal to the engine management system, which will reduce engine torque (by reducing fuel) until the differential is corrected. This torque reduction is handled in stages, and reaction time is extremely fast. The system can be switched on or off by pressing the button on the center console for at least half a second (see page 27). The indicator light () in the instrument panel will be ON when you have switched the system off. The STC system comes on each time you start your car.

The STC indicator light () will come on for approximately 2 seconds when the engine is started as the system performs a self-diagnostic test.

This system should be switched off if you, for any reason, temporarily have to drive with tires of different dimensions (e.g., spare tire).

The symbol will flash when STC is actively regulating power to the drive wheels. Normal power may be reduced at this time. This is normal as power is momentarily reduced to help keep the drive wheels from losing traction and spinning.

If the STC system has been switched on using the button in the center console (the indicator light will normally go off) and the indicator light remains on, there is a fault in the system. In this case:

[JRL]

Terrific
But that all doesn't matter.
You should NOT be feeling all this above 25 or so, the system just does not supposed to intrude like that unless you are having seriously poor traction issues.
I have sold and driven many S80's, the ONLY time I ever felt his was off the line under a full throttle shot and that was only for a split second
You have a DSC, DSTC (if equipped) or a transmission issue, remember almost all T6 trannies go bad at some point (sorry)

[BLKS80T6]

Late reply but it may help others......It is the TCV - Turbo control valve. Also know as the BPS - Boost pressure solenoid. It is attached to the side of the airbox. I had the same thing. Surging or steps of power under hard acceleration. A new TCV solved it straight away.