that problem on xc90 6 cylinder is bad gearbox they to many problems with gear boxes you need to check for fault codes it is possible that you can fix the problem with software update to the ecu but most the time gearbox is bad the xc90 new gearboxes are much better when you replace it

ask if you have more questions

i understand you if you can give the fault codes from the scanner im sure when you use the advanced scanner on the transmission it will tell me more what is going on .

why it slips the clutches on transmission get worn out like on manual transmission or the springs and bands inside trans just don't hold and car will slip also one thing that also takes out that trans is coolant leak from radiator small amounts off coolant mix oil in trans thru the radiator and when they mix it takes out trans out , also on left wheel if you take out the center bolt for the axle is behind the Volvo center cap on the wheel if you get oil leaking out that you axle has failed and the grease mixed with trans oil taking trans out also , what you have on your car regular gm transmission is not Volvo gm made it for Volvo but with very poor results

let me know what else you like to know i can send you only picture of transmission and connecting parts

the pictures i send you can open that that is the main pictures all other picures are just volvo log what is not showing it

each number is XXXXX refernece on the pictures part number and name i will try resend you one more time see if is better