Ok guys lets see if your up for a challange!!!!! 2002 monte SS 3800. Drives like a dream till she warms up after about 30-40 min hiway driving then starts to clunk when shifting, handling is effected as well as braking pulls and can feel resistance in acceleration.

160 kms tranny filter has never been changed.

 

Sounds like your car just needs a complete tune-up. Check all filters, all fluids, all everything.

What's the handling problems? Need some tire rebalance and alignment?

Honestly you could be killing the transmission if you never changed the fluid or filter. Drop the pan and fill it up and put in a fresh filter. If it keeps up, you could just be too far gone in never doing routine maintenance and killed the shift solenoids.

www.tripleedgeperformance.com is some good transmission reads

 

going to get parts now to change filter and fluid hopefully its the fix and not to late!
cheers chibi