Vibration at thirty five MPH

Tires wont cause a vibration at such a low speed unless one has a broken belt or a wheel is bent. One observation is whether the vibration is felt in the steering wheel or the seat and armrest. A broken belt in a front tire will cause a shimmy in the steering wheel that may only be felt at lower speeds, like when driving through a parking lot.

The next time you feel this vibration, hold the accelerator pedal perfectly steady, then with your left foot, lightly tap the brake pedal. If the vibration stops for about two or three seconds, then comes back, suspect the transmission's torque converter. Those typically lock up at around thirty five mph for better fuel mileage, and they can cause a chatter that may or may not be rather subtle.

Has any brake work been done recently, or anything that required removing the wheels, (before you had the new tires installed)?

Sorry that I was not thinking about the struts. There has to be more to the story because struts do not cause a pull unless one is so badly worn that it lets that wheel lean in on top. The car needs to be aligned when struts are replaced, and the affected alignment angle is what causes a pull.

Since engine mounts are involved, I should also have asked if this vibration only occurs during acceleration? If it does, there is likely a worn area in one of the inner CV joints. That will cause the rollers in the joint to bind when they're under load, meaning accelerating.

Low fluid could cause a vibration, (shudder), from the torque converter's clutch assembly. They lock up when the engine is warmed up, you are above approximately thirty five mph, you are in third or fourth gear, you are not pressing the brake pedal, and the throttle is not at idle or wide-open-throttle. Tapping the brake pedal causes the clutch to unlock, (in preparation for coming to a stop). That is why that clutch is suspect if the vibration stops when you tap the brake pedal.

The shudder can also occur on some car models if the wrong transmission fluid is used. That most commonly occurs shortly after the transmission has been serviced. In some cases it takes perhaps a year or more for the needed additives to become depleted, when the wrong fluid was used, before the vibration shows up.

The clue here is the shudder occurs much more rapidly than a tire balance problem. A bent wheel or broken tire belt will be felt once per wheel revolution. That is considerably slower than what you would feel from the torque converter.

That's what we are here for, please let us know what happens.

Best, Ken

You might want to rethink the "getting ripped off by an expensive unnecessary repair" We DO want to avoid the "ripped off" part, but a lot of times we think we know the answer and we recommend the appropriate service, then we are just as surprised as you are when we find out that wasn't the solution. Funny how we never question doctors when they're wrong the first time. What would be the point of intentionally selling you a service when we know we're going to have to explain why we were wrong.

Often we have to perform a number of tests before one of them provides the clue or information we need to make a diagnosis. Similarly, often, in the name of saving you time and therefore, money, we have to quickly try things instead of wasting time with a lot of tests that take longer to provide the same results. The problem is sometimes you don't have time to wait for us to try all those things, so we'll pick the most likely thing, then have you drive the car to see if the problem is solved. We expect you to come back, but we often do a very poor job of communicating why that is necessary. The alternative might be to keep your car for a few days, and neither of us wants to see that bill!

This story is a perfect example of what can go wrong. Whose idea was it to go after tires and balancing? If you asked for those services, you can't blame the mechanic for doing what you asked for, but you could also say you got ripped off for unneeded services. If the mechanic took the car for a test-drive, and you pointed out the vibration, that is his fault for not recognizing the symptom. Either way, you ended up with something you didn't need, but that doesn't mean there was no value for what you spent.

The best clue you provided was that this occurred consistently at around 35 mph. That's what prompted me to bring up the torque converter, but not everyone is familiar with this problem. Everyone at a tire store should know a tire balance problem won't cause that, but a wobbling wheel will. Somewhere someone's thought train got derailed.

I'm actually dealing with this right now on my daily-driver minivan by, ... Uhm, .... Not dealing with it! I'm pretty sure it has the wrong fluid in it from the previous owner, so I just live with it. You should take the mechanic on a test-drive and be sure to point out that the vibration stops when you tap the brake pedal. If a shop says the transmission needs to be rebuilt, that is the time to get a second opinion, preferably from a transmission specialty shop.