WS-Six

iTrader: (1)

I have a vibration issue with my 98 T/A and have had it for a while now. I just can't seem to fix it...I replaced my flowmaster exhaust with the SLP loudmouth about 5 months ago, and ever since i did that i have a vibration running through the car when it's in gear. It is felt when the car is at a stop. At first i thought the exhaust was running too close to the driveshaft, so i readjusted it and reclamped all the pipes and it STILL does it. What could be causing the entire exhaust to shake and send vibrations through the car? Oh and also, the driver's side y-pipe shakes quite a bit too? Any input would be fantastic! Thanks!

-Ryan

crapyboy750

Man i have the exact same problem as you do but instead i have a borla exhaust
I aslo have a post up too see if anyone will help me with the problem if i find out ill let you know.

MasterV8

iTrader: (7)

I also had the same problem! changed transmission mount & installed y-pipe bump stop with no luck, thought it was the merge collector hitting the tunnel!
Turned out the upper most bolt on the y-pipe hanger was loose & banging around because the garage that installed my new cats had cross threaded the bolt & just left it!

crapyboy750

if that is what the problem is do you think its a big deal on not getting it fixed

WS-Six

iTrader: (1)

If that's what it is...i dont think it's a big deal to not have it fixed. I guess it all depends on weather or not it bothers you. I have actually gotten used to the vibrations since it's been that way for about half a year...but i would LIKE to stop it as long as its not a huge project lol! I think my problem is coming from somewhere around the cat under the drivers side ypipe.

crapyboy750

Like my vibrate like starts out just the little shake from the exhaust but after the car has been in the same gear and is just sitting there it really starts to shake hard.

UCABlackChevy

iTrader: (10)

I think I have the same problem with my Hooker exhaust. If I sit at a red light while the car is idling really low the vibration becomes a shudder if I blip the throttle. I think it does the same thing under medium acceleration at about 2k-2.5k rpm then it shifts and the vibration/shudder goes away. When you figure out what it is post up.

WS-Six

iTrader: (1)

yeah those are the exact same symptoms that i am having...im wondering if it has to do with the change in back-pressure? Although before my SLP exhaust it had the flowmaster with no vibration....hmmmm..

HAZ-Matt

iTrader: (8)

My car is doing something similar. Stopped in gear it will vibrate if it is warm. It does not vibrate in park or neutral. It also is completely smooth after I give it some gas and when it is cold. This started after I got the Dynatech LTs and LS6 H/C put on. I haven't had a chance to get under the car yet to check out the Y and make sure it isn't hitting the floorboard.

A-RoN'sZ

I have a 98 Z28 w/ a flowmaster cat-back and everything else is stock, and I'm having the same prob. When it's in neutral or park...nothing, but when it's in gear and I'm on the brake I hear like a metal banging against metal vibration that sounds like it's coming from the driver's side Y. Also, when I take off and the auto is going through first and shifting to second it does the same, but after the shift second and the following gears are fine. I haven't really had time to check mine to see what's going on.

WS-Six

iTrader: (1)

Well mine isn't a metal hitting metal sound, its just a vibration. Good news is i have a good idea as to what is causing your sound. Check the heat shield on the drivers side of the y pipe, and see if it is coming into contact with anything.

5301113

iTrader: (18)

Maybe the vibration is because of the motor mounts. If the motor mounts r old or broken they may cause the exhaust to move more than normal. If you get aftermarket exhaust and they are lighter the stock exhaust they will move more. If the motor is moving more with broken motor mounts and lighter exhaust it rattles .
My two cents

Check your mounts

crapyboy750

Ya like WS-Six said its not a metal against metal vibration its just a vibration that takes over the whole car.

5301113

iTrader: (18)

IS your car Auto or Stick?

5301113

iTrader: (18)

If is Stick

Motor mounts are easy to check. Put the car in 1st, hold the brakes and ease the clutch out without stalling it. Have a friend watch the engine for excessive rock. Do the same thing in reverse. I can tell you from experience the motor mount on F-body's are NOT fun to replace, even doing it in a fully equipped garage with a lift.

You should not be getting excessive vibration in the wheel and shifter at idle. I have poly mounts all the way around and I don't have a problem. I'd be concerned that they didn't balance the pressure plate and flywheel when they did the clutch or that a bolt could be working its way out of the pressure plate. Taking a look at the tranny mount couldn't hurt.
__________________
MIKE44138 put this on another forum

5301113

iTrader: (18)

If it's Stick

Motor mounts are easy to check. Put the car in 1st, hold the brakes and ease the clutch out without stalling it. Have a friend watch the engine for excessive rock. Do the same thing in reverse. I can tell you from experience the motor mount on F-body's are NOT fun to replace, even doing it in a fully equipped garage with a lift.

You should not be getting excessive vibration in the wheel and shifter at idle. I have poly mounts all the way around and I don't have a problem. I'd be concerned that they didn't balance the pressure plate and flywheel when they did the clutch or that a bolt could be working its way out of the pressure plate. Taking a look at the tranny mount couldn't hurt.
__________________
MIKE44138 put this on another forum

UCFWS6

iTrader: (4)

I had the same problem for some time with my loudmouth and finally solved the problem. My problem was that the rear passenger side hangar would not hold the over the axle pipe away from the frame. Found it while installing sfc's at an exhast shop. The guy ended up loosening all the clams around the over axle pipe cutting off the stock hangar, re-adjusting the pipe as far towards the drivers side as possible and then kinda half *** welded a new hangar on and no more vibration. So jack ur car up and look at the over axle area of the exhast.

UCABlackChevy

iTrader: (10)

Seems logical, will have a look at it after work.

HAZ-Matt

iTrader: (8)

That makes a lot of sense. It sounds like the bulk of the vibration is coming from the rear.

Z28UK

I've got the vibration too, really bad! I've got a Euro-spec Z28 thatwas fiitted with the V6-style muffler with single outlet from the factory (to make them quieter). It was so quiet you couldn't hear it was V8 at all, so I changed it to a hooker dual outlet and immediately the vibration started. I removed it all again, installed a dual outlet stock style muffler and it still does it. I've had the exhaust on and off dozens of times. I get a really really bad vibration (no noise with it) that comes through the steering wheel, gear lever, floor, really nasty and when starting the car, the whole car shakes, feels almost like the exhaust has been welded to the frame of the car!! -i've checked and double checked and it's definitely not touching the body -it's driving me mad trying to fix it. I've got a 3rd gen firebird too -never had this problem with that and it has a louder flowmaster fitted... I've got a new cat on order thinking it might be that (though doubt it) -any other ideas?! You don't think it's possible the engine was tuned a bit different for a single outlet?? -doesn't really make sense though to me.. thanks