Too much vibration with brakes applied in DRIVE at stoplights.

[Legback]

Seriously, you think that brake fluid is creating a vibration from your engine?

 

I've got ocean front property in Kansas that i'll sell you cheap. QUOTE]

 

I wonder not "THINK" if wicked old brake fluid loses some of it's turgor and causes more exertion from the brake system.

 

I like the cv axle idea much better even though in a million years it wouldn't have occurred to me!

[NoahDL88]

Brake fluid is hygroscopic so it is a good idea to change it out every 3-4 years or so, but it won't add much to the effort you need to push the pedal down unless there is air in the system.

 

I usually judge it on the beer scale, if it looks like lager its great, if it looks like a pale ale its got some time left, if it looks like a dark ale/stout, its time to swap it out.

 

Did you try the parking brake instead of the regular brakes?

[Manarius]

Noah, there often isn't an actual engine problem to cause the vibration. The stackup of tolerances in a worn or shoddily rebuilt axle let the power pulses of the engine vibrate the car, and replacing the axles can often make the issue go away.

 

The real problem is that the torque converter stall speed was designed too low, so the hydraulic coupling at idle speeds is too strong. If a higher stall torque converter was used, it's connection at idle speeds would be much "looser" and the power pulses wouldn't be transmitted through.

 

The brakes are not the problem, the mounts are not the problem, and nothing is really "broken". The vibration is a mild annoyance, and clicking it into neutral when sitting stopped will make it go away. You can push the shifter into neutral without depressing the thumb button so there's no risk of going into reverse on accident. My mom's been doing that for years with her Outback. It's a "design feature" of the too-tight converter. Not an actually problem or failure per say.

 

Buicks, Olds, and Cadillacs of the mid 60's had "switch pitch" torque converters, that had a variable stator blade angle. It would switch between a high stall and a low stall torque converter. They switched into high stall when the throttle was closed in the idle postion to uncouple the engine from the drivetrain, to eliminate this exact vibration problem. The converter was then switched to low stall as soon as throttle was applied to keep the engine RPM's low and the fuel economy better. If you planted the throttle wide open, it would switch back to high stall to get the engine up in it's peak torque rpm range.

This post. Right here. This is why the vibration happens. The TC's stall speed is exactly the issue.

 

I disagree that axles can vibration at stop (axles don't move when stopped, so, why should they shake). Every AWD car I've owned has had this mild vibration when stopped and in drive. I just put the car in neutral. Even at 191k miles, I have no problem popping the car back into gear, waiting a fraction of a second, and then going again. It's not even a minor inconvenience. It makes me feel like I'm driving a MT

[Legback]

Putting it in neutral at stoplights works and seems like the easiest thing to do. It's nice to know I'm not the only one with this disease. Thanks to all for your interest and input!! (sorry)Didn't mean to -Trev

[SoobrDad02]

Great posts everyone! Can this count as my "something new learned every day" for today? Seriously though, everyone on this board is a huge help, whether it's because they've asked the right questions or because they've given the right answers, this board is immensely helpful! Thanks everyone!

[curtisbad]

i had exactly the same problem with my 97 ej25. the fix for me was removing and cleaning the IACV. i took it off, sprayed it down with carb cleaner and scrubbed it with an old toothbrush. that , a new gasket and some new bolts and i have no prob with the vibration anymore. hope this helps. curtis