My 97 GTP has been making a single clunk sound each time I start rolling after starting the engine. It's been doing it for years, but it used to only do it the first startup each day. Now it does it if I park the car any longer than 10 minutes. If I "park" it and leave it running, nothing happens. Also, when it makes the noise the headlights and dash lights (if they're on) dim for that split second. If I happen to have my foot on the brake, it softens up and the brakes cease to function for that split second (kind of scary when backing down a steep driveway!).

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'97 GTP: 3.4, 3" DP, P-Log, TR55IX, FWI, 160*, Ported S/C and heads, XP, 105's

on my car, the ABS tests itself, and almost sounds like a grinding noise, If you gently rest your foot on the pedal it will feel like a slight vibration, could this be what your experiencing?

Pull the abs fuse and see if it still does it?

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2002 GT...Wizardair, ZZP 2.5 o/r dp, Special Eddition two-tone leather interior added, HUD added, 12" Brake Upgrade, ZZP strut tower bars, gmpp sway bars,-6an braided SS fuel hoses , Hptuned, Top Swaped.....
I've got Boost!! I've got only 1.5* KR left my poor L36 block.....

Check your cradle bolts.

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Dark Teal 97 GTP - 3.69 tranny - 2500 stall - XP cam - 130# springs - Ceramic ZZP Z7 62-1 - air to air intercooler with Turbonetics Raptor BOV - 72mm ported stock throttle body - 65# injectors - Autolite 103s - custom 3" exhaust

Sounds like this is the problem. Mine does the same thing. Lights dim a bit. Makes a grinding like sound. Everything is normal.

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1997 GTP - 196xxx miles, PEMs, 3" SS Exhaust w/ Borla Mufflers, 3.4", 180* stat(summer), FWI, 1.84 RR, PT, SLP hood, KYB GR2s, GMPP Handling Kit, etc...

I'll try the ABS fuse and see what I get from that tomorrow.

Also, it used to turn on the ABS and Parking Brake lights sometimes when it did it. That has since ceased with the replacement of both front wheel hubs. Should I check out the rear ABS sensors?

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'97 GTP: 3.4, 3" DP, P-Log, TR55IX, FWI, 160*, Ported S/C and heads, XP, 105's

^^^ that makes sense, it was finding the errors in the hubs and setting off the system...... Tell us what happens when you pull the fuse, the abs light should be on(otherwise you pulled the wrong fuse :P )

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2002 GT...Wizardair, ZZP 2.5 o/r dp, Special Eddition two-tone leather interior added, HUD added, 12" Brake Upgrade, ZZP strut tower bars, gmpp sway bars,-6an braided SS fuel hoses , Hptuned, Top Swaped.....
I've got Boost!! I've got only 1.5* KR left my poor L36 block.....

I had a "clunk" as well so I replaced the front DS wheel hub assy about 3 months ago and am now starting to run into the same problem. There's more symptoms. Car pulls a little to the left, theres a metal scraping sound (kinda like the break pads are worn, but they're not) when turning left, and occasionally when breaking I feel/hear a metalic grinding sound. I hate to think the wheel hub is bad again, but I heard that it is not uncommon to get a bad one.

Does anyone know if there is something I'm missing? Could there be something else causing the wheel bearing to go bad?

^^^ did you go GM or cheap, I've heard of the cheap ones going out after a few days....

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2002 GT...Wizardair, ZZP 2.5 o/r dp, Special Eddition two-tone leather interior added, HUD added, 12" Brake Upgrade, ZZP strut tower bars, gmpp sway bars,-6an braided SS fuel hoses , Hptuned, Top Swaped.....
I've got Boost!! I've got only 1.5* KR left my poor L36 block.....

I pulled the ABS fuse this morning, and have been driving it around all day like that. No noise now. The whining from (I'm assuming) the power steering pump also seems a bit quieter, but that may just be my imagination. So, what do I do now? Drive around without ABS, or is there something more specific I can tinker with?

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'97 GTP: 3.4, 3" DP, P-Log, TR55IX, FWI, 160*, Ported S/C and heads, XP, 105's

That means that you are hearing the normal ABS self-test, It is just something we all live with, I would suggest putting the fuse back in now that you know what the noise is

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2002 GT...Wizardair, ZZP 2.5 o/r dp, Special Eddition two-tone leather interior added, HUD added, 12" Brake Upgrade, ZZP strut tower bars, gmpp sway bars,-6an braided SS fuel hoses , Hptuned, Top Swaped.....
I've got Boost!! I've got only 1.5* KR left my poor L36 block.....