Acceleration noise

**GMPUNK** · 04-21-2009

So yesterday I installed a 3.5 pulley and overkill pcm in my 01 GTP, and i have all the supporting mods. I noticed if i take-off fast enough to break traction my car makes a bumping noise, the dash bounces, scared the hell out of me.At all other speeds the car is fine, even in first, no noise unless I break traction. It never done this before the pulley and pcm. Any ideas?

**Bio248** · 04-21-2009

sounds unrelated to the pulley and mods done unless it is your headers hitting....if you have headers...

**blowfishRus6** · 04-21-2009

kind of sounds like violent wheel hop

**Bio248** · 04-21-2009

since when do these cars get wheel hop? never heard of it..

**GMPUNK** · 04-21-2009

Yeah, Don't think it's wheel hop. To better describe it, when the tires loose traction theres no bump and as long as i keep them spinning loose there no bump, the bump occurs when the car regains traction or i ease off the pedal,. it doesn't matter if traction control is on or off.

**Bio248** · 04-21-2009

sounds like something on the front end might be loose? i would check your mounts, cradle bolts, LCAs, etc.

**GMPUNK** · 04-21-2009

somebody mentioned about the dog bone mounts maybe being bad. is there a way of telling by looking at them. I had a friend keep going from drive to reverse while i looked at the engine and it does seem like it rocks alot just going into gear, how much movement is normal?

**blowfishRus6** · 04-21-2009

i wheel hop all the time. 235's with about 32 psi gives pretty good traction.

**Bio248** · 04-21-2009

maybe your hitting the firewall with the motor? that would mean your lower mounts are trashed.

Originally Posted by blowfishRus6

i wheel hop all the time. 235's with about 32 psi gives pretty good traction.

you sure about that? ive never heard anyone with a grand prix talk about wheel hop. ever.

**GMPUNK** · 04-21-2009

is it normal for the engine to move like an inch when going for reverse to drive? I don't get any other noises over bumps. Would bad dog bone mounts cause this noise?

**blowfishRus6** · 04-21-2009

Originally Posted by Bio248

you sure about that? ive never heard anyone with a grand prix talk about wheel hop. ever.

yea. i could show you the hop in the marks. bogger has also talked about wheel hop when hes at the track.

my upper bushing on my front struts are shot tho. might have something to do with it. the motor mounts are new so that is about the only thing i can think of.

**GMPUNK** · 04-21-2009

If one of the lower mounts were bad would it only do it when the tires spin from a stop then grip, it doesn't awalys do it every time. I was wondering if it could be something with wills tune and im hearing the tranny bumping, i dont want to mess my tranny up.

**blueguy** · 04-21-2009

Meh, not really. You might try flipping the stock rubber mounts from vertical to horizontal. That is a nice, free mod and gets rid of a lot of movement IMO. If not, Autozone sells solid replacement mounts pretty cheap IIRC...Abrasive has the part numbers...

**blueguy** · 04-21-2009

It would only really show if it was bad during a shift or load on the motor. Might send him an email and ask him...Overkill PCM right?

**GMPUNK** · 04-21-2009

Yeah it's on overkill, it seems to be too much of a coincidence the day before the pcm and pulley i had no noise, i picked it up, it was raining and spun by accident and heard it. It kinda sounds like if you were to be rolling backward and pulled it into drive before coming to a stop ( i've never done that before in this car). The thing that gets me is that once you get going enough to nail it without spinning theres no noise,and no noise at any other speeds or when it shifts. Its more from a stop than if you were to roll into it before spinning it. when i say from a stop i mean i am hitting it just hard enough to spin maybe a foot, i've never dona a long burnout with it.

**blueguy** · 04-21-2009

Originally Posted by GMPUNK

Yeah it's on overkill, it seems to be too much of a coincidence the day before the pcm and pulley i had no noise, i picked it up, it was raining and spun by accident and heard it. It kinda sounds like if you were to be rolling backward and pulled it into drive before coming to a stop ( i've never done that before in this car). The thing that gets me is that once you get going enough to nail it without spinning theres no noise,and no noise at any other speeds or when it shifts. Its more from a stop than if you were to roll into it before spinning it. when i say from a stop i mean i am hitting it just hard enough to spin maybe a foot, i've never dona a long burnout with it.

So it is only when the tires are spinning...I'd check your CV Shafts, and hell...your Diff too might be goin out on ya...just a thought...

**GMPUNK** · 04-21-2009

But what are the chances that the day i put the pcm in that the problem occurs. you think that i should put the stock pcm in and see if it still does it? i don't know if that will be ok to use the stock pcm with the 3.5.

**99prixgt** · 04-21-2009

i get a good amount of wheel hop on half throttle going from a total stop.

**blowfishRus6** · 04-21-2009

i dident think i was the only one that got it.

maybe its the new power you have the mounts are starting to go bad. but if the dash is shaking its more than a poping mount. either the motor or something is hitting, or........... your wheel hoping.