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pachotrod 05-01-2002 04:16 PM

shaky brakes
I need help. I have a 1984 GMC full size Jimmy 4x4. When I apply the brakes ithe front end shakes, real bad sometimes. At first I thought my lug nuts were loose. Not! I tok it to a well regarded suspension place and before I could finish describing it he told me it was the front rotors. He says they're warped and need to be turned or replaced. Sound about right to everyone? What could it be?

36fatfender 05-01-2002 05:03 PM

I agree,I think the rotors are warped,also check your bearings.

jenkinra 05-01-2002 07:33 PM

Pachotrod - warped disks will definitely cause the vibration you have noticed upon hard braking. They warp with normal use, but especially when the brakes are held on after a hard stop (the pads concentrate the generated heat on a small area of the disks). This is most likely to happen with an automatic transmission, since you would normally keep the brakes on after stopping. I always make a point of lifting off the brakes after a stop (any stop) to relieve the pressure (and heat) on a single spot of the disks. Just let it roll forward or back a little and reapply the brakes if you need to - it does make a real difference. The other thing to check is the adjustment your wheel bearings - this vibrating under load doesn't do them much good and they may loosen up.

pachotrod 05-05-2002 05:02 AM

Thganks guys, never thought about the heat of the pads thing. Really makes a lot of sense though. Thank you again.

Pontiacman 05-05-2002 08:59 AM

Just a thought, I'd take weight off front suspension, and grab ahold of tire and shake, wiggle, up, down, side to side. also might be a combination of things showing themself if tie rod , pitman, or idler arm bad this would also magify this problem. also wheel bearings not being seated properly. make sure your cure involves all factors described, for a total cure. just a thought, hope this helps a little

dmorris1200 05-05-2002 04:54 PM

Yes generally if the front end only shimmies while you're applying brakes it's the rotors. But if you let off the brakes and she continues to shake, I have seen a bad steering stabilizer do this in a few Jeeps. Don't know if the Jimmy uses a stabilizer or not. Just something that came to mind. :)

gbovaird 05-05-2002 06:07 PM

Usually if the rotors are warped bad you will feel the brake pedal pulse up and down a tiny bit also. You can also jack up the front and spin the wheels with your hands and alot of the time you will have the wheel slow down or stop only in a few places through one rotaion. Generally brakes dont have a lot of clearance between the pads and the rotors and any warpage will usually be felt. HINT , If you do your own brakes always, always make sure the caliper and its sliding mechanism are working good, if the caliper is not allowed to float , it will warp brakes in no time. Always torque the wheel nuts , i have seen on front wheel drive cars especially , that if they are tightened with an impact gun it may give you the warped rotor feel also. I have also seen where worn front end components would give you this problem , so dont ever count them out. good luck !

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