I have a question for the car geeks out there. if at around 40mp-70mph, there's a tad bit of a vibration/rumble you hear/feel coming from the back, what could it be? The car doesn't have a shit ton of miles on it (for it's age), and it did get new tires relatively recently. It doesn't vibrate under 40 (or if it does, it's not noticeable), and it's fine @ idle. if you take the car out or gear in that speed range, it doesn't change the issue. It doesn't change with the speed you are going either (in that it doesn't speed up/get louder if you are going faster). any ideas? I'm suggesting the person have the tires checked for balance, and hoping that is the issue.
Take the tires off and have him just drive on the rims. If the car still shakes you know it's not the tires but something else.
sounds like you have a tiny unicorn in your exhaust, jumping around and poking holes in everything to get him out: 1 dig a large hole and place caulking all around it (unicorns love eating caulking) 2 fill hole with wood and light on fire; burn until completely ash 3 when the unicorn comes out to taste the caulk, kick him in the ash hole
verify your tire pressure is correct and the same for all tires. Inspect for visible flaws on the tread. verify that all the tires on the vehicle are the exact same model and are the exact same size and have the exact same wear and measure exactly the same diameter. Rebalance the tires. Most likely, the tires are not balanced. If none of the above helps, could be alignment, shocks, suspension.
I'm by no means a car geek, but I've faced similar issues in my 'Rolls. If the tire balance doesn't take care of it, check out the wheel alignment as well
I'll look at the car again soon, and check out the tires a little more. I only had a little time to help this person and they aren't really helpful with these kind of facts.
I agree with what's been said re balance, alignment, etc if it's happening when driving. Other alternatives (albeit much less likely) are the axle if it happening while moving (once had an axle basically fall off once the car got lifted), or the rotors if it's happening when braking. I have to get my front rotors machined for uneven wear. It shakes the steering wheel a lot when I break. Rear rotors could shake the back side of the car.
