Hello all. I’ve got a strange drive train issue. I’ll try my best to describe the symptoms I feel:

The car jerks to the right. Not all the time, but in spurts. Almost like the left and right front wheels become unsynchronized and the right one spins a little faster than the left and jerks the car to the right.

It only happens when I apply very light throttle. When I’m accelerating it doesn't do it. When I’m coasting it does not do it. It seems to only happen when it rains and when the car has been driven at highway speeds for about 1.5 hours. It has never done it in the city, only on the highway.

More recently, once I got off the highway after driving for 3 hours it was doing it as I came to a stop on the off-ramp and at the following two red lights, slowing in frequency as I stopped. I shifted the car into neutral as I was slowing down at one of the red lights and it still did it while coming to a stop.

I took it to my Volvo person and there were no error codes on the computer. I haven’t been able to reproduce it and the only other times it has done this to me was earlier this year in May after driving for 4 hours on the interstate and then again this year on a trip to Colorado from Florida it did it only once and I pulled off to the side of the road leaving the car on and in park, took some pictures by the “welcome to Colorado” sign, got back in and continued to drive and then not a peep.

An alternate description of what it feels like is that it feels like only the right caliper engages the brake at light throttle, pulling the car to the right. My brake lights work fine. Cruise disengages when I tap the brakes as it should.

If I hold the throttle lightly, to try and induce the jerking and hold the wheel, if I do that long enough the whole car begins to shudder rather violently until I let off the throttle or accelerate.

Go figure. Any ideas?
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-Hector