VY Shudder at 60 & 80 km/h

[alien]

I noticed today 3/4 of the way through a drive to Hawthorn from Maribyrnong that my car was shuddering at 60km/h and reluctant to pick up speed. After i did break 60km/h, it did it at 80km/h as well! Shuddering was felt through the whole car (passengers mentioned it) and the vehicle didn't sound too healthy at those points either.

On the reverse trip hours later it was back again, however it seemed to dissapear half way through the trip. Not sure if that was due to the rain hiding it or whether it just toned the shudder right down.

No check powertrain lights or any other lights or alerts on the dash when this happened either. And vehicle passes startup test.

Any ideas as to whats wrong?

I am fairly sure it's not to do with the engine or the wheels as it only happens at the two speeds mentioned above. Which leaves me with two thoughts:
1. Joint in driveshaft or diff [CV or UV]?
2. Torque Converter Clutch (which does explain the 80km/h shudder but not the 60km/h shudder)

What do people think? One of those? Or other problems? e.g. 1-2 Solenoid or 3-4 Clutch?

[keza87]

It could possibly be the torque converter clutch as I have noticed that it will in fact lock-up in 3rd gear when doing 60, so don't rule it out just yet.
It may be that it's locking and reluctant to unlock