its gonna be a long one, so here it goes:

about 2 weeks ago, i got an apexi dunk cat-back and after installing it, i notice a rattle around 1500 rpm. it turns out there is some sheild that hangs over the point where the A pipe and mid pipe connect. that shield is pretty much touching the pipe, and i see no way to solve that problem other than removing the shield which i probably wont do. anyway, today while i was driving on the freeway, i feel this weird vibration in the cabin at around 2500-3000 rpm in 5th gear. at first, i didnt think too much of it until it got pretty darn noticeable. it almost felt like my engine was misfiring, but it wasnt. when i get to my house, i check my plugs and wires, just to make sure they werent the problem. then i check my oil, which i had just changed about a week ago (mobil 1 10w-30), and i notice that it was about and 1/8 inch above the top hole on the dip stick. the first thought that came to my mind was that i spun a bearing. since the oil change, i think i've only taken my car up to around 7000 rpm and it got me thinking. i asked a friend, and he said that if i spun a bearing, my engine would have been revving pretty high, but the car would have been very sluggish. i'm not really sure if he was correct or not, but for the most part, it was a sign of relief. when i got back home from work, i drained the extra oil out of the car, and now its pretty much in the middle of the two holes. i checked all the bolts on my exhaust to make sure they were still tight. i also put in new ngk copper plugs (bkr6e-11) to replace the crappy bosch platinums which were just temporary until i bought the ngk's. i reset my ecu and everything, and when i took her out to the freeway, i still got that damn vibration. i dont know if i'm just hallucinating or if its just the loudness of the dunk that causes the vibration in the cabin, but its getting on my nerves. when i would get the vibration, i would almost be flooring it around 2500-3000, where it would happen. when i accelerated normally through the same rpm, i didnt feel the vibration. i dont know if i'm trippin' out or not, but i would really appreciate some comments on what you guys think could be the cause of this, or if its just something i'm making a big deal out of. anyway, sorry for the long post. TIA.

edit: oh yeah, i forgot to mention, its a 98 GSR w/ about 41K miles




[Modified by GSR44, 2:39 AM 8/6/2001]

 

I've got this same **** happening to me at around 3100rpm. It sounds like a loud rattling noise coming from underneath my car. Its SOOOO annoying! People are telling me that its the heat shields, and that its ok to remove them. I might just remove my exhaust right now, and put the stock one back on to see if its really the exhaust doing it.

 

try putting on headers I had a similar rattle at 3500, put on some headers and the noise just went away!

 

From what he described, it doesn't sound like the infamous a-pipe rattle. I'd take a look at removing your exhaust heat shield that's touching your exhaust. I took mine out recently and it's doing just fine.

One question: Have you installed a shortshifter at all?

 

If you don't want to remove your heatshield, another option is to bend it at the points where it's touching your exhaust pipe. That's what I did. To do this, you'll probably need a car lift and a crowbar or long screwdriver.

 

i already have i/h/e. about the short shifter, i'm not sure if the GSR already comes w/ a shorter shifter than most cars, but my friend says that its pretty short. i bought my car w/ the dc header and a custom exhaust already on it, so i dont know if there's a short shifter on there or not. its still black, so i'm guessing its the stock one, correct me if i'm wrong.