Wierd vibration in Drive...

[StuntmanMike]

I get this wierd vibration when in drive on the highway if I leave it in Drive and not OD. It starts at 1800rpm or so, then builds to a really noticeable point at 2k rpm and above.

At that point, if I put it in OD, the rpms drop, converter locks, and it smooths out. At this point I'm doing 1700rpm or so.

If I take it up to 2000rpm and beyond (which is where I get the bad vibe in D) while in OD, it's still nice and smooth, no vibes.

Now it's not really a noticeable problem, since I always use OD on the highway, but I know it's not right.

Any idea what could be causing the vibe at 2k in D, and not 2k in OD?

Thanks!

[razer900]

I have basically the same thing your describing as well. I changed motor/trans mounts this spring and noticed more vibes at certain rpms. I guess thats what i would blame in my case anyway. I dont know about your situation tho. Have you changed any mounts recently?

[StuntmanMike]

Nope, I haven't changed anything.

Also, I don't seem to notice the vibe at 2k when it's shifting, like through first then second, but on the highway in 3rd I notice it.

[Supershafts]

Make sure your trans is tight, nothing loosed up, otherwise the vibration issue is at the trans or tc

[StuntmanMike]

I was paying more attention to it over the past few days, it seems like I DO get the vibe at 2k while it's shifting through the gears.

I definitely don't have it at 2k rpm in OD though.

I almost want it to be a TC issue, that'll give me an excuse to get a stall, haha.

Now what do you mean by "tight"? Check all the bolts and mounts?

[GA_muscle]

DOes it do it if your at a stand still at the same rpms?

[StuntmanMike]

DOes it do it if your at a stand still at the same rpms?

Good question, I haven't tried that yet. I only noticed it in gear, never thought of trying just revving the motor to 2k in neutral. I'll try that next time I go out.

[JaycenK]

Power brake it too. Even on a stock converter you should be able to hit about 2k rpms.

[Smittro]

Check your torque converter and torque arm bolts..

[StuntmanMike]

Ok, I sat in it with it in park, and brought the motor up to 2k rpm...and yup, it has that same vibe. It vibrates all the way up to 3k rpm and a little beyond, but seems to smooth out after that.

No SES light, and it seems to run pretty good other than that vibe, and a slightly rough idle (which bugs me also). I've vleaned the MAF, TB, IAC, changed the PCV, sprayed Deep Creep in the intake, and nothing has cured the rough idle. I've been told by multiple people that they just run that way.

Anyway, if it does it at a standstill, I'd imagine that rules out the torque arm bolts. Any other ideas?

Thanks!

[2002blackz28]

I started geting a small vibration also when I acc. light or hard. Not sure what it could be. I looked at the U joints but they seem fine. I hope I can find out what the heck is going bad or broke

[Smittro]

I started geting a small vibration also when I acc. light or hard. Not sure what it could be. I looked at the U joints but they seem fine. I hope I can find out what the heck is going bad or broke

torque converter bolts or the unit itself..

[Cutlass]

Ok, I sat in it with it in park, and brought the motor up to 2k rpm...and yup, it has that same vibe. It vibrates all the way up to 3k rpm and a little beyond, but seems to smooth out after that.

No SES light, and it seems to run pretty good other than that vibe, and a slightly rough idle (which bugs me also). I've vleaned the MAF, TB, IAC, changed the PCV, sprayed Deep Creep in the intake, and nothing has cured the rough idle. I've been told by multiple people that they just run that way.

Anyway, if it does it at a standstill, I'd imagine that rules out the torque arm bolts. Any other ideas?

Thanks!

With this new info, I believe your problem lies somewhere in the engine. If its just an engine vibration and not a running issue, then it sounds like you have a balance issue. Typically that means the balancer(front of motor), flywheel/flexplate, or torque converter are out of balance.

[StuntmanMike]

With this new info, I believe your problem lies somewhere in the engine. If its just an engine vibration and not a running issue, then it sounds like you have a balance issue. Typically that means the balancer(front of motor), flywheel/flexplate, or torque converter are out of balance.

D'OH! I guess I should get this fixed sooner than later.

Any easy way to check these things, or is my best bet just taking it to a shop?

[Cutlass]

you could look at the balancer while the engine is running and see if it wobbles. Also look at it with the engine off to see if the rubber looks rotten/nasty/falling apart.

[StuntmanMike]

More experiments with it today... I left it in 1st, and there doesn't seem to be a vibe there while at 2k...same thing with 2nd, no vibes at 2k.

So it seems like it only does while not in gear, or in 3rd.

I watched the balancer while the motor was running, it seems to be running straight and true, and visually looks okay.

Also, while I was under the hood, I revved the motor with the throttle linkage, and the motor doesn't appear to have any shake to it, at least that I could notice.

[Marc 85Z28]

I had the same problem, like every other single exhaust F-body in existance. After putting in a new engine and trans/converter (not for vibration issue), it was still present. Had a dual exhaust system fabbed up, and noticed on the first drive how much smoother the engine and car felt overall. No more exhaust vibration.

[JaycenK]

Do you have polly motor mounts or a polly trans mount? I don't know about LS engines but the LT1 used a weight on the flex plate. Anyone know if the LS1's used a weighted flex? If they did make sure the weight is still on the flex plate. Also make sure the bolt holes on the flex are not way out of round. If you have it in park then it's engine related. Polly mounts however are famous for transfering noise and vibrations that are normal into the car where you hear and feel it.

[StuntmanMike]

Nope, all stock rubber mounts as far as I know. The car was bone stock when I bought it, so I don't see why it would have had poly mounts anywhere.

[2002blackz28]

torque converter bolts or the unit itself..

Yes you nailed it on this one. I had a few bolts loosen up. Now there good