When I shift to drive/rear from neutral/park, I can . hear low-key humming noise and slight vibration. Transmission shifts fine when driving. Is there anything to worry about or check?
Thanks so much!
Respectfully disagree with some of this, my good sir. 😉
According to many educated sources, You really DON’T want to flush it under high pressure if it has accumulated a lot of mileage. A fluid change is necessary (disregard dealership claims that it’s a lifetime fluid) but do so gradually and carefully. My Volvo indie shop said they did some process that ran new fluid in while old fluid went out, doing so until the transmission fluid ran all clean, moving fluid in and out using the car’s own transmission pump or some **** like that. Wish I had a clearer understanding of the process but they and nearly everyone else has said that a high pressure flush on a higher mileage transmission can stir up a lot of crap that can get stuck in the wrong places and can also lead to slip within gears. I realize my utterly amateurish description of the principles and methods I’m trying to describe makes me sound like a moron, lol, but trust me, lol.
That having been said, your transmission should be drained and refilled, but PLEASE be sure to have someone who is a Volvo specialist and not a transmission shop generalist, do the job, because the transmission requires a very specific procedure using VIDA to get the fluid level right. Even my dealership got the procedure wrong when they replaced my transmission under warranty and assumed the new transmission was “a sealed unit” therefore it HAD to have the correct fluid level from the factory, right? WRONG! As a result I had 40k miles of terrible, slushy, inconsistent shifts and greatly reduced throttle response and slower acceleration. After 40k miles and multiple visits where they refused to check levels properly or do a service outside of the “lifetime fluid” schedule, I had a reputable Volvo indie change the fluid and refill it to properly to spec. I cannot overstate what a difference it made. It felt like someone had removed my Polestar tune and now I had it back. Crisp, consistent up- and down- shifts, and my car moved off the line quicker and with much sharper throttle tip in responses in general. Long story short, a tiny volume of fluid was all it took to make or break the driving experience, so be sure to get the job done by people who are knowledgeable and attentive enough to do the job perfectly, and who will use VIDA to do the job right.
And finally: it’s probably NOT your transmission creating the issue you’ve described, even though transmission maintenance should be done to ensure longevity (but not as often as some people might recommend, which to me creates more oppprtunity for error or contamination of some sort, or is merely wasteful...try every 40k miles or so), but likely worn motor mounts as someone already mentioned. There’s a torque mount at the top front passenger side of the motor, which has rubber that tends to rip and create a lot of back n forth engine movement that will be felt as a lot of drivetrain lash when you get on and off the throttle suddenly.
Do you feel slop or a sensation of bounciness in the drivetrain making it hard to give smooth throttle inputs? If so, that points to the tq mount needing to be replaced. That might help your issue, although once that part wears out, it can accelerate wear on other mounts that may also need to be refreshed. There’s a mount underneath the torque mount that supports engine weight and which tends to sag and is known to create extra vibrations as a result, so perhaps you should replace both at the same time for good measure.
Someone recently did a good write up in one of the P3 subforums which details the process which seemed doable to a competent home DIY shade-tree mechanic. You’ll have to search for that writeup, but in the meantime, here’s a pic of the torque mount and the other mount underneath it, which are probably the source of and the solution to, your vibration problem. Guaranteed your car will drive like a dream once you replace them.