Hi, I have a Lumina Sedan year of construction 98 and if I brake the brake / or the whole cat stutters the, but it is not the engine, the engine goes on nicely around, so if I brake Wobbling the car body and with go on further.
In front I have changed the brake pads in last years, the test 2 months ago the car has existed successfully and brake value are OK.
Mine oppinion is the brake fluid, coz i think the fluid is 3 or 4 years old.
Can be the sign for old liquid?

It sounds like it's a warped brake rotor to me.

You mean the discs? I have checked and they are all ok...

How did you check them, with a dial indicator to determine runout?

No i havent a dial indicator, I checked they with my eyes..

You cannot check for warped rotors with your eyes only, both the ft and rr rotors or drums out of round or warped can cause your symptoms, you need the proper tools to check them, anything over .005" can cause this shudder you describe.

Ok thx, i will check it and come back to report.
Did anybody know which tor I need when i want change the discs? I have new here.
Its an 1998 with 3.8L

Metric socket set for the caliper and 60 Torx socket to get the caliper mount bracket off, make sure the torx drive socket is a heavy duty 1/2 drive, these bolts are very tight.