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Discussion Starter · #1 ·
curious what your guys thoughts are on this vibration problem.

1996 LT1-ODB2 (duh), stock tranny, stock TC, aftermarket intake, shorty block hugger headers. Rebuilt stock 4l60e tranny (bad pump)

While in motion under load (leaving a light), I get vibrations through out the car.
Once at a reasonable RPM, it starts to smooth out.
Once at a higher RPM, vibration comes back, but much more mild then from the light under load.
I can see the crank dampening pully vibrating very slightly at idle and through the first 1K of RPM. The thing is, it is visible (maybe .1" runout (maybe 1/16"))

So, I place the car in Neutral, and the vibrations are still present, and in relation to RPM.

I've taken the three torque converter bolts off and spun the TC into all three positions. This may have helped, or may have been a placebo effect (i *think* it changed, but it really didn't).

I've used search and noticed that a few folks mention removing the accessory belts and running the motor like this for a bit. Is it dangerous to do? Can I go for 5 minutes on just the battery like that?
This will confirm its the A/C, P/S, or alternator, right? (oh, Alternator is 'new' AutoZone rebuild).

All fluids are checked and up to spec (color/smell).

I'm trying to narrow this down to either the accessories or the TC.
Is there anything in the transmission that would cause this vibration while in Neutral?

Please, ANY single mild or wild guess would be helpful as I battle this problem.
Thanks SO much guys!
 
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Discussion Starter · #2 ·
Oh yes, I also diagnosed that I do not have a mis fire or ignition problem.
I inspected all spark plug wires (aftermarket).
I removed fuel injector connections one at a time and notice a stumble in RPM (cyclinder going dead, proving spark and fuel are present).

I do not have a consult type software or whatever to read codes. Damn, I really need one of those things...maybe someday.
 
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Discussion Starter · #3 ·
Thanks for everyones help so far! this forum ROCKS :rolleyes: Guess I'll use this forum as my personal notepad for things I've done so far so I can look back as I fight this.

Removed the accessory belt. Didn't even have to take it out of park, the vibration appeared even more prevelant. Bummmer. Guess I'll do a TC next. I suppose it'd be a waste of time to put a wanted ad in the classifieds section. I'd only be talking to myself. Right, nixit? Right nixit!

 
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Discussion Starter · #4 ·
Have you chacked you drivetrain ujoints on your drive shaft, trans mount, maybe its your posi. how bad is the vibration at higher speeds?.
i hop this helps.

Is it more like hesitating then vibrating problem maybe? :rolleyes: :rolleyes:
 
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Discussion Starter · #6 ·


Yes, I did use search extensively (very extensively...two days worth of search as a matter of fact. I never ruled anything out).


It's not in the u-joints/axle.
It makes the vibration in Neutral, in park, in reverse, and in drive. This proves it's not from the output shaft back.
the vibration is strongest at roughly 1K rpm, and tapers off around 1.5k through roughly 3K, where it comes back, but is just a slight vibration.

In search, I also read of a cracked flex plate weld. Where can I see this? on the ring gear? or closer to the center hub?

I'm hoping somewhere out there had a torque converter that was bad, but still functioned correctly. The torque converter is a remanufactured unit from an unknown (perhaps shady) source. The unit seemed to have worked fine when I did my first motor R & R, but it was not driven on at that time, only idled/reved.

I should probably come clean and mention something. I didn't think it would make a difference to my problems tho.
I bought a SS motor and tranny to put in my jeep wrangler. :D I know. Blasphamy. the tranny was modded with a new output shaft and end housing to accept the 4wheel drive transfer case. nevertheless, with the car in neutral, no power gets to the transfer case, so I know this is not an issue.
From the transfer case forward, it's essentially bone stock.


not a very upto date photo, as the intake has changed. (use a shorter 1le intake now)

I was really hoping some of the hardcore folks out there would know or be helpful.

-regards,
nixit.
 
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Discussion Starter · #7 ·
Despite the attitude in your third post, I'll throw out this thought for what it's worth (maybe not much). If the problem got worse when you took the belt off, maybe it's your harmonic balancer. It makes sense that the tension from the belt would help tame a vibration problem there.
 
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Discussion Starter · #8 ·
I think it might be the harmonic balancer too, I have seen these go bad before, it isn't exactly a stout piece on a stock LT1. Are there any signs of wear on the balancer? I know you said you can see a bit of runout on it and that doesn't sound healthy to me, my harmonic balancer is perfectly smooth when the engine is running.
 
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Discussion Starter · #9 ·
Mike/Erik, the donor motor was in a front end collision. I had to replace the air pump (deleted anyway), the alternator (crushed vanes/bent shaft), and the Idle Air sensor. So it stands to reason that it is a potential balancer issue. I thought of that, but didn't think the balancer could produce that kind of vibration. (it can be felt in your butt and on the steering wheel (car not in motion)).

I can see what you mean about the vibration getting worse when the belt is off, since the accessories aren't dampening any of the vibration. I'll try that next then (beats a TC swap!)
 
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Discussion Starter · #10 ·
<BLOCKQUOTE>quote:</font><HR>Mike/Erik, the donor motor was in a front end collision. I had to replace the air pump (deleted anyway), the alternator (crushed vanes/bent shaft), and the Idle Air sensor. So it stands to reason that it is a potential balancer issue. I thought of that, but didn't think the balancer could produce that kind of vibration. (it can be felt in your butt and on the steering wheel (car not in motion)). <HR></BLOCKQUOTE>

I've got kind of a dumb observation to add here. While the engine is running does the balancer appear to be running true and not wobbeling? While you were under the car with the converter inspection shield removed, did you start the motor and look to make sure the rear of the crank was running true?
Did you or anyone else have to replace the oringinal balancer?

I have seen cranks bend in front end wrecks, something you may not want to hear but true none the less.

I would remove the belt and see it goes away, next I would remove the converter bolts and push the converter back away from the flywheel and try it again, if it continues..... I think you get the just of where this is going.

IMO
Dennis
 
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Discussion Starter · #11 ·
BTW I forgot to add a balancer can cause what you are feeling. It's job is to cancel harmonics/vibrations that a motor produces while it is running. Our engines have what is called a neutral balance balancer and fly wheel, no extenal balancing weights added, where as a 400/383 type motor and the 454 has external weights added to both the balancer and the flywheel to an extra offset weight because the internal counter weights on the crank weren't heavy enough to make those motors internally balanced.

Now that I made a simple answer long, the balancer can cause that.

dennis :D
 
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Discussion Starter · #12 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by dloch:
Our engines have what is called a neutral balance balancer and fly wheel, no extenal balancing weights added, <HR></BLOCKQUOTE>

Actually, you're half right. The balancer IS neural but the flywheel isn't. There is a weight on one end of the FW. My 383 is interally balanced and uses the stock neutral balancer. I had to knock off the weight on the FW so it now becomes neutral as well.
 
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Discussion Starter · #13 ·
I have not had my trans out yet fot the rebuild and converter so I was guessing on the no weight of the flywheel as every small block I have done none have had any weight added to the flywheel to give it a neutral balance, none were LT1's either.

Did you get the crank as a neutral balance?

Another question, can the balancer be installed incorectly on the hub? Just a thought.
 
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Discussion Starter · #14 ·
<BLOCKQUOTE>quote:</font><HR>While the engine is running does the balancer appear to be running true and not wobbeling?<HR></BLOCKQUOTE>.
YES, that was covered in my first post i believe.

<BLOCKQUOTE>quote:</font><HR>While you were under the car with the converter inspection shield removed, did you start the motor and look to make sure the rear of the crank was running true?<HR></BLOCKQUOTE>
I had a chance to peak under the car and saw that the balancer appears to not be rotating smoothly. It doesn't appear to be balanced properly. I will remove the three bolts holding the TC and start the car up. This will prove whether it's in the motor or aft of the flexplate.

<BLOCKQUOTE>quote:</font><HR>Did you or anyone else have to replace the oringinal balancer? <HR></BLOCKQUOTE>
It is a remaned unit (stock impalass) TC. It was replaced during my install. Again, this was a preventive mainenance issue. If it can be swapped easily and was a smart part to 'freshen' the motor, I replaced it.

<BLOCKQUOTE>quote:</font><HR>I would remove the belt and see it goes away,<HR></BLOCKQUOTE>
Yes, I did that. Vibration appeared worse. But I may have been more sensitive to it. (again, placebo type situation.)

<BLOCKQUOTE>quote:</font><HR>next I would remove the converter bolts and push the converter back away from the flywheel and try it again, if it continues..... I think you get the just of where this is going.<HR></BLOCKQUOTE>
I agree...I'll try that as soon as I possibly can
 
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Discussion Starter · #15 ·
This is a shot in the dark but what about the engine mounts? I would check to make sure the motor and trans is sitting tight before you pull the transmission.
 
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Discussion Starter · #16 ·
motor mounts are brand new and custom fabbed. there is no play in any of the motor mounts.
thanks for the idea.

I didn't get a chance to disconnect the TC from the flexplate last night. I'll shoot for this weekend.
And since the motor can be run with out accessories for a bit, I may try removing the dampener too.

I do appreciate you guys and your thoughts.
 
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