Need help figuring out what is wrong with my GFs car

[BD2003]

I'm a bit stumped by this one.

The car vibrates when driving, directly proportional to speed.

It's not the tires, they are balanced fine, inflated fine, and nice and round. I dont think it's the suspension either, bumps dont make it any worse. Can't really feel it in the wheel, other than the shaking of the car wobbling the loose power steering, so I dont think its anything to do with steering or wheels at all.

I thought it could be a bank of cylinders misfiring, but theres no knocking, it doesnt get worse under load, and its proportional to wheel speed, not engine speed.

A funny thing I noticed: Her driveway is a pretty steep hill. I took the car out of park and put it into reverse - and I didnt roll back. Put it into neutral....and I didn't roll back. Parking brake wasnt on, my foot was off the brake pedal. Gave it a little bit of gas in reverse, it hesitated, and came to a stop shortly, while still on the hill. Got on flat ground, put it into D, and it didnt creep forward.

So that leads me to believe the brakes are sticking somehow. There's no grinding, the front rotors look alright, so do the front pads. Rears are drums, and I dont even think they've ever been relined in ten years. The car doesnt pull to either side, braking or not. I would think if the rears were worn to sh*t, theyre be grinding and all sorts of noises, rather than them sticking too well. But I cant say I know much about drums. She seemed to think it got worse after she braked hard here or there, but I didnt notice that.

But after I drove the car around a bit, it did begin to creep forward in D, back in R, and it rolled easily down the hill in N like a good little slushbox should. There is also a pretty wicked jerk from time to time when switching from D to R. So that leads me to believe the tranny is acting a bit funny...but doesnt explain why it would still stay on a hill in N..that has GOT to be brake related, no? The parking brake cable is also intact, and seems to disengage fully.

Right now, the shuddering is so bad, its undrivable. Any ideas?

 

[bctbct]

maybe a stuck caliper or colapsed brake line since you talk about it being worse after hard breaking sometimes.

edit

If the brakes are sticking it will cause the rotors to warp and cause shaking. Although you should feel that in the steering wheel especially when you brake

 

[BD2003]

Originally posted by: bctbct
maybe a stuck caliper or colapsed brake line since you talk about it being worse after hard breaking sometimes.

But if a caliper was stuck, wouldnt it be pulling to one side?

I find it hard to believe that two brakes would stick at the same time, without one going before the other. I could imagine both brakes wearing evenly, but then they would stick less, rather than more I'd assume, and there would be some wicked scraping or grinding, especially on braking...but theres none. The fluid level is also fine, and the pedal feel is fine as well.

 

[bctbct]

Originally posted by: BD2003

Originally posted by: bctbct
maybe a stuck caliper or colapsed brake line since you talk about it being worse after hard breaking sometimes.

But if a caliper was stuck, wouldnt it be pulling to one side?

I find it hard to believe that two brakes would stick at the same time, without one going before the other. I could imagine both brakes wearing evenly, but then they would stick less, rather than more I'd assume, and there would be some wicked scraping or grinding, especially on braking...but theres none. The fluid level is also fine, and the pedal feel is fine as well.

if the caliper is sticking you will get more dust, grinding only occurs when the pad is gone.

it seems brake related since you said it did not want to roll down the hill and there is a shaking.

what does not make sense is that you dont feel it more in the steering.

I have had a collapsed brake line, brake-pulls right/left-still pulls right/left since the brake wont release.

warped the rotor, caused a shimy driving down the road, but it was bad in the steering wheel.

 

[xXped0thugXx]

It could be warped rotors and or calipers sticking. It always doesnt affect the steering wheel, but you will be able to notice when you step on the brake.

Also just throwing it out there could be an axle problem. My buddy's axle was ready to go and shuddered much like the description you gave. Directly proportional to wheel speed, didnt feel it in the steering wheel.

CV joint? Just throwing some stuff off the top of my head.

 

[BD2003]

Originally posted by: bctbct

Originally posted by: BD2003

Originally posted by: bctbct
maybe a stuck caliper or colapsed brake line since you talk about it being worse after hard breaking sometimes.

But if a caliper was stuck, wouldnt it be pulling to one side?

I find it hard to believe that two brakes would stick at the same time, without one going before the other. I could imagine both brakes wearing evenly, but then they would stick less, rather than more I'd assume, and there would be some wicked scraping or grinding, especially on braking...but theres none. The fluid level is also fine, and the pedal feel is fine as well.

if the caliper is sticking you will get more dust, grinding only occurs when the pad is gone.

it seems brake related since you said it did not want to roll down the hill and there is a shaking.

what does not make sense is that you dont feel it more in the steering.

I have had a collapsed brake line, brake-pulls right/left-still pulls right/left since the brake wont release.

warped the rotor, caused a shimy driving down the road, but it was bad in the steering wheel.

Well the rotors are fine - they've been replaced fairly recently, and they arent visibly warped or scored, and the pads are thick enough. That was the first thing I checked. I doubt it's the front discs...if it's the brakes, I'm guessing its the drums in the back.

 

[AMCRambler]

Based on what you described, it does seem like a brake issue. Easy enough to check though. Jack up each corner and make sure each wheel spins freely. Note you will need to put the car in neutral to turn the drive wheels. Make sure you chock the wheels on the ground when you do this! If it's the rear wheels you're not able to turn, that's probably a bound up parking brake cable. If it's just one wheel, I'm thinking more likely a froze up caliper or wheel cylinder.

 

[bctbct]

I doubt drums would cause shaking. Could be bad belts in a tire. Unrelated to the locked up brake problem.

 

[saymyname]

pics?

 

[SmoochyTX]

My last car had this problem one time.

Turned out it was the emergency brake sticking on the rear (don't remember which side).

ETA - Honestly. It took us forever to figure it out until we took it to a friend that did brake jobs.