Bad VIBRATIONS.

[madmike3.8II]

So I just got back from a drive around town, and I'm really, really pissed off. I dunno whats going on, but I've never had a vibration issue with this car. (97 3.8 RS) everything is bone stock on it.
so while driving I was coasting from ~45 approaching a stop, when I was still coasting down to about ~35 this nasty shake came from what felt like the right rear. and it stayed until about 15/20. I shifted through the gears next couple times to see if it was a tranny issue, but it didn't do it again. so I dunno what the deal is. the tires are alll ~42 psi, but there is one issue I've had through winter...I noticed the other day my rear control/sway arm was hanging down, and the bolts were missing, seem to have lost them in the snow. but it's been that way for a few weeks until i get the parts ordered, and I haven't had any problems except for body roll into corners (which I don't take fast) anyway. I'm still pretty pissed I dunno what the deal is. any suggestions? thanks!

[Blizzard242]

Re: Bad VIBRATIONS.

Bad pavement. All your lug nuts tight? If your certain it came from the rear maybe it's time to look into the rear diff. A fluid change wouldn't hurt anyways. Were you on the brakes at all? Get that sway bar fixed man.

[madmike3.8II]

Re: Bad VIBRATIONS.

Bad pavement. All your lug nuts tight? If your certain it came from the rear maybe it's time to look into the rear diff. A fluid change wouldn't hurt anyways. Were you on the brakes at all? Get that sway bar fixed man.

i don't think it was the pavement...did it on several occasions. im gonna jack her up and check the diff fluid now. I've heard everyone comment on how "weak" the stock rear end is...but this sucker only has 65,000 miles on it. and I don't beat on it...unless I see a mustang...lol checking tire pressure and torque too. I would like to upgade to disk brakes in the back someday too, so I figured why not just get a new diff and brake set up alltogether...any suggestions?

[whitdog54]

Re: Bad VIBRATIONS.

I run 35psi on my tires...but, doubt thats the problem.

Check to see if a wheel weight came off maybe? Check lug nuts as well.

Also maybe a bad wheel bearing? or axle. Just throwing out possible ideas.

[97rs4life]

Re: Bad VIBRATIONS.

just does it slowing down? How about 55-60 mph?

[Mark42]

Re: Bad VIBRATIONS.

Check the U joints in the drive shaft also. If they are worn they can cause the drive shaft to move off center and vibrate. They usually make a clunk noise when shifting from drive to reverse.

I doubt you damaged the rear, unless you are racing and doing 6k neutral drops, the rear will hold up just fine in your car.

[madmike3.8II]

Re: Bad VIBRATIONS.

well, the first thing I did was check the torque on the wheels. all of em were snug to 90ft-lbs so then I jacked her up and was checking the differential fluid, which was full. so I started moving up the driveshaft, and this is what I found :(

the carrier bearing wore out...and I'm glad it's not worse. so I'm tryin to find a cheap one fast. when I was under there I found the source of my rattle too. the "L" bracket that comes off the tranny mount for the exhaust catalyst broke off right at the catalyst. so I might try to just repair it by welding it in place for now...don't really have the money for a new cat right now...but of course another mod I'd like to do later down the road. full exhaust and intake..

thanks again for all your help, any further would be icing on the cake :) ...and I like Icing

[97rs4life]

Re: Bad VIBRATIONS.

time for a ls1 alum driveshaft! save a bunch of weight and eliminate the carrier bearing. $100-$150

[Mark42]

Re: Bad VIBRATIONS.

time for a ls1 alum driveshaft! save a bunch of weight and eliminate the carrier bearing. $100-$150

yep, an aluminum shaft is a nice upgrade. And it is a direct bolt in. Call around the salvage yards and see what you can find. I paid $75 for a used LS1 shaft and two brand new in the box GM heavy duty universal joints.

If you are in a hurry, the stock steel one piece shaft will bolt right in too. Should be cheap at a salvage, about $20-50 or so.

I just put in a LS1 aluminum shaft in place of the steel one piece. You can notice a difference under the right conditions, like downshift to pass, etc.

Here is a comparison between the stock steel and the LS1 aluminum. I polished up the LS1, so don't expect that they will look like that at the salvage yard :)

[madmike3.8II]

Re: Bad VIBRATIONS.

haha, yeah. I guess so. I was calling around trying to get a part number for the center support bearing, and beating my head against the wall as to why nobody could find it, then I figued it's time to give in and call GM for a price >_< and they want $890 for a new drive shaft assembly :omg: so I guess I'm calling junk yards. akron pull apart has 2 97's sittin in their lot, but there's no telling what kind they are. cleveland east and west have a 91, 94, and earlier...like 80's... any other model's besides the LS1 that have and aluminum shaft? or even steel...it's a daily driver...not a big deal for me, though it would be nice. Any ideas on where i might find one? im near cleveland, ohio

[Mark42]

Re: Bad VIBRATIONS.

haha, yeah. I guess so. I was calling around trying to get a part number for the center support bearing, and beating my head against the wall as to why nobody could find it, then I figued it's time to give in and call GM for a price >_< and they want $890 for a new drive shaft assembly :omg: so I guess I'm calling junk yards. akron pull apart has 2 97's sittin in their lot, but there's no telling what kind they are. cleveland east and west have a 91, 94, and earlier...like 80's... any other model's besides the LS1 that have and aluminum shaft? or even steel...it's a daily driver...not a big deal for me, though it would be nice. Any ideas on where i might find one? im near cleveland, ohio

Any 98 or later V6 fbody will have a one piece steel drive shaft. All Trans Am are supposed to have an aluminum shaft, but apparently not all actually received it. Don't know about the other models.

The steel shaft from a 98 and up is your best bet if you are on a budget. Might want to install a new set of U joints in the shaft before installing. Its a bit of a pain, but if the ones that come with the shaft are good, just go with them. It took me about 20 minutes to swap out the shaft on my car once it was up on stands. Once the old two-piece is out, the one piece will go right in and you will be driving inside of 15 minutes.

One tip: Be sure to completely clean the trans yoke of all rust before installing. This is because you don't want the tail shaft seal riding on a rusty yoke surface. The rust will wear out the seal out and then the trans will leak. Just take some 400 grit wet/dry paper, spray the yoke with WD40 or some other light oil, and sand off any rust until its all clean. Also, don't forget to smear a thin coat of grease all over the yoke (inside and out) before installing as per GM service instructions.

[Blizzard242]

Re: Bad VIBRATIONS.

Hey, glad you at least figured out the problem. Some part failures can be a good reason for an upgrade! And cheaper sometimes. Good luck.

[Unique96Camaro]

Re: Bad VIBRATIONS.

yep, an aluminum shaft is a nice upgrade. And it is a direct bolt in. Call around the salvage yards and see what you can find. I paid $75 for a used LS1 shaft and two brand new in the box GM heavy duty universal joints.

If you are in a hurry, the stock steel one piece shaft will bolt right in too. Should be cheap at a salvage, about $20-50 or so.

I just put in a LS1 aluminum shaft in place of the steel one piece. You can notice a difference under the right conditions, like downshift to pass, etc.

Here is a comparison between the stock steel and the LS1 aluminum. I polished up the LS1, so don't expect that they will look like that at the salvage yard :)

Thats what i did to. Mine was a 2 piece drive shaft and the coupler broke so me and my welder make one from scratch.:D