If you are not convinced it is a torque converter, then do a flush at home with either the cooler line or drain/fill method since it is very affordable. Ironically, with many transverse mounted engine/transmission vehicles, bad mounts can cause a weird vibration or thump. The warmer temps make it worse because the already loose rubber becomes softer, allowing for more movement. Load on acceleration can also bring this out.Sorry, I'm new to this and very green!
It's a 2007 xc 90 V8, (B8444S), so it is a 4.4
When I purchased the car in the winter, I noticed a slight shutter, but was told from the seller it was a bad engine mount. Since I got the car at a reasonable price, I rolled with it. Now that it's warmed up, the shutter seems to have gotten worse. Before diving in and ordering a ton of parts to replace the bad engine mounts, I brought it to our local mechanic (who specializes in German Autos) to look and confirm my suspicions. Unfortunately, he felt it was a Torque Convertor and told me to go to a transmission specialist to confirm this. I've talked to several transmission guys in our area and they all told me to go to a dealer and that they didn't want to touch it. The nearest Volvo dealer is 4 hours away, so I want to check all possible boxes to ensure it is indeed a torque converter. Some of the posts I've read earlier suggest doing a transmission flush or putting in additives to solve this problem. I'm still not entirely convinced it is the torque convertor, but not sure what else there is to look at.