Vibration on Toyota Tacoma?


I have a 97 Toyota Tacoma pickup, 4-wheel drive, 5-speed, manual transmission that has a pesky vibration problem(s). When I brake hard, I feel a slight vibration as the car decelerates (sort of like the brakes are rapidly going on and off, but more subtle). It seems to be originating from the front wheels or undercarriage. My mechanic balanced the tires as well as replaced the front brakes, rotors, and calipers, but the problem remained exactly as before–no improvement. I also feel a vibration when I am not breaking, but traveling at speeds above about 40 mph, and I feel a pronounced vibration when the engine is working while accelerating, especially in 4th gear trying to gain highway speeds. The best way I can describe it is like driving a car at too low a speed in too high a gear or driving a car with one bad cylinder–the engine grumbles and struggles to gain power and speed. However, this is just the feeling–the car actually has no problem attaining highway speeds.

It might sound like an engine problem, but when I rev the gas while idling, the engine sounds smooth and responsive. It seems to be only when there is a load on the engine or when I am braking that I experience the vibration.

I have researched symptoms of bad tie rod ends and bad hubs/bearings and some of the problems I am describing seem to relate, but not fully.

Any suggestions would be appreciated.

Have the tyres rotated. If it moves you know it is a tyre or wheel. I suspect a wheel is bent. Do you have alloy wheels rather than steel? Consumer grade alloy wheels are more subject to being bent than steel. One hit of a pothole can do it.

It might pay to check your motor mounts. If one is going out, it could produce the symptoms you describe. Do you hear any “clunking” when engine is under load?

Sounds like a bad u-joint to me.

Thanks for your replies. I brought it to another mechanic this week, and after test driving it, could not determine what the problem was (although he agreed there was a problem). He suggested taking it to the Toyota dealer to do some computer diagnostics. Some possibilities that were tossed around at the shop were: bad u-joint, bad bearings, bad motor mounts, improper fuel mixture. I’ll post the solution here when it finally gets fixed.

Wild guess- hit any poyholes hard recently w/front tires? Front end been hit in an accident at one time? Axle flange could be bent. Would only take .020" - .030" deviation- something on that order- to cause braking vibration, since rotor, wheel, and tire are “indexed” to flange. I machined front rotors on a car once that had a pulsating brake pedal; it didn’t solve the problem and then I found the deviating axle flange- car had been in an accident in recent past.