Vibration in car at high speeds

[eazyemk]

I bought this car 2 weeks ago.
I have a 2002 5-speed corolla with 79,000 miles. The car runs and shifts very smooth at low speeds.
problem: Once I hit 68-69 mph (It is always at this exact speed), the car noticeably starts to vibrate, I can feel it in the steering wheel. I depressed the clutch, and the car still shook, so it is not an engine or transmission problem.
cause of problem: (My idea)
There are 3 old tires on the car, each need to be replaced in the next 500 miles. There is one new tire, rear right, that was replaced due to a flat by the previous owner.
This brand new tire is slightly different than the others because it has new tread on it. (because of this, it has 3-4mm of extra tread on it which makes the circumference of the wheel greater) Could this difference cause this vibration?

[mr1114]

Since you know you need tires, replace them and that will most likely take care of the problem (as long as they're properly balanced).

[ilovecorollale]

Sorry to bring this thread up but mine is a auto and it vibrates at 60 and up mph. this morning i drove to school on highway and it was gone which is weird...and i know its not my wheels cuz i just balanced it and tires are still new. And i read that it could be the motor mount worn out cuz i tried the shifting into P down to R and the engines does shift forward and back like alittle inch and that is what causes the problem but i dont think it is the motor mounts.
i drove it on highway at 65 mph where it vibrates alot and then i switch gear to neutral and it still vibrates originally....so if it was the motor mounts then when i switched to neutral the engine should have relax and calm down not needing to work hark hard to maintain that speed right?????

or am i just pointing a wrong stupid point here....please correct me.thanks

[bail_w]

Originally Posted by ilovecorollale

Sorry to bring this thread up but mine is a auto and it vibrates at 60 and up mph. this morning i drove to school on highway and it was gone which is weird...and i know its not my wheels cuz i just balanced it and tires are still new. And i read that it could be the motor mount worn out cuz i tried the shifting into P down to R and the engines does shift forward and back like alittle inch and that is what causes the problem but i dont think it is the motor mounts.
i drove it on highway at 65 mph where it vibrates alot and then i switch gear to neutral and it still vibrates originally....so if it was the motor mounts then when i switched to neutral the engine should have relax and calm down not needing to work hark hard to maintain that speed right?????

or am i just pointing a wrong stupid point here....please correct me.thanks

I am having the same problem with new tires and i am suspecting that either one or more cyclinders are misfiring at at that speed (65mph). When virbrating at 60 - 60 mph, i feel the car lost horsepower. I am going to replace my ignition coil packs and spark plug wire set and let you know.

[jbod]

mine has a similar problem, but it doesn't really start at any speed exactly. not really vibration as much as it is just a road feeling. i am thinking either motor mounts or tires. myself, and other friends don't really know how to work on front wheel drive vehicles. i won't take it to a mechanic, because they will want something ridiculous like $1200 bucks probably unless it is only the tires. i have to get my tires replaced soon anyway, because they are starting to dryrot as well as the tread wearing.

[Automechnic077]

Im having the same problem at about 55+ only on the DE accleration while staying in the gas the car is fine but as soon as I let off the car will begin to shake. Nothing severe but enough to notice for sure. I have narrowed my problem down to the CV joints when acceling they have pressure applied to them and theyre fine but whel de acclerating they begin to wobble. Get under it and see how much play you have in them. Play is fine and ive been told therye ok but when they begin to click while turning its time fro them to go. btw my Prizm has 179,000 miles on it