Braking Vibration/Shudder

'98 4Runner vibrates/shudders when braking at 50 mph or above, and stops when speed is below 45 mph. Anyone know what the likely causes are?

Also, what kind of mileage should I expect to get on the original clutch? I have been the only driver of the vehicle since new.

The front rotors maybe warped.

Depending how you drive, you should get 100-120K miles out of a clutch.
Some people even more, others even less.

Hi ....it may be a bad rotor I had one warp on me and it did what u are discribing?

The pulsations or vibration is caused by warping and/or hard spots forming in the rotors. These are caused by overheating.
The rotors can be turned but the hard spots remain and will become symptomatic again the first time they get really hot.
Having the surface ground will help even more but again the vibrations will come back.
The rotors over heat for a couple of reasons, hard driving and braking, continuous down grade braking, and the MOST common reason is not rebuilding the calipers when new pads are installed.
When new pads are installed the pistons must be forced back into the cylinders where contaminants have collected, the cylinders are natural sediment collectors, thus the pistons bind and do not allow the pads to release or back off the rotors causing great amounts of heat due to friction.

I have had cars in the shop that the rotor was blue from heat because the owner had always just “stuck in pads” and called it good.
You can get away with not rebuilding the rotors once and maybe twice, but the proper procedure and if you have to warranty your work you MUST rebuild the calipers.
Don’t cut corners here, I mean just how important is stopping anyway.

Thanks for the tip. I replaced both calipers, but kept the rotors and brake pads. The vibration is minimal now, but like you said, the problem could very well return.

Could this type of problem occur with the rear drum brakes?

I'll keep you posted.

Could this type of problem occur with the rear drum brakes?

Drum brakes will eventually wear into an "egg shape" oval that can sometimes cause pulsations. This can be verified by lightly engaging the emergency brake, if you get pulsations, then the only brakes being applied are the rear drum brakes.
The rotors on the 4Runners are too light duty for the weight they are required to stop.