Rockit_GTO

Well, no luck with the dealer on mine. They put a case in with GM Tech to see if anyone else is having problems.

I wish they would just admit the motor is out of balance. Either the factory balancer is not doing it's job or the crank is unbalanced. Of course, the ever wonderful piston slap is probably not helping.

97Silverbullet - A converter is definitely the single best mod that I have done to date. I would definitely do it again. Although, with the lack of other mods on my car, the 3200 stall is a bit much for everyday driving.

97SilverBullet

Well thanks for the info, do you think a vig 3000 is a lot also? That is what i was planning on. How does getting a staller affect the regular driving performance (non- racing).

maddboost

iTrader: (11)

I have a similar vibration in my car around 2500 to 3500 rpms with my VIG3800 stall. I had the converter sent in to be flushed and Precision Industries said nothing about it.

CrimeSScene

iTrader: (9)

I like having a larger stall converter. It doesn't affect my daily driving at all except to rev to about 2000 rpms before really taking off. I would have to recommend it. I think the vibration in my car was there to begin with and that the smaller converter just didn't dampen the vibration as much as my larger stock converter. Once you get used to the feel of the converter, you won't even notice that you have one. I would actually suggest going as big as you think you can stand as far as stall goes. I've only had mine for a month or so and I feel like I would probably be fine with a 4000-4400 stall. I will say that I can't speak as far as how a converter will feel without a cam. I would think it would be the same though.

97SilverBullet

ok,thanks

PSU_Engineer

I hate to bring this thread back, but I found some info that may be interesting to the people that have responded to this thread.
In the current issue of HotRod,(yeah I know ), the part towards the back where people write in problems with their cars has a blue box surrounding a message written by a GM tech. In that message he describes a similar problem with a 3d gen Camaro with a 700R4 transmission. Since our trannys are basically a 700R4 with electronics, I could see this being relevant here.
I apologize for not having more info on this. If anyone has this HotRod and can transcribe the mechanic's wording I think it would be beneficial for all to read. I will find the issue tonight and type it in, unless someone here can (hopefully) beat me to it.

Tony

CrimeSScene

iTrader: (9)

Just FYI, I turned my converter one bolt hole last night. It definitely changed the vibration. It doesn't vibrate as bad at lower RPM's but It feels worse around 2000-2500. The pulsating is much more pronounced. I'm gonna try and turn it one more time and see if that helps, if I can remember whether I turned it clockwise or counterclockwise . This is driving me nuts .

maddboost

iTrader: (11)

When was your converter bought?

CrimeSScene

iTrader: (9)

I don't know originally, I bought It used from a member of this board about 1 1/2 months ago. He never had any problems with vibration as far as I know.

Rockit_GTO

I would blame the converter if we had not taken the converter off and the vibration was still there. With the converter off, the vibration was still there at the same RPMs. Therefore, it either has to be engine related or exhaust related and I've done everything I could to eliminate any exhaust related issues.

Anyone else try it with the converter off to see if they still have the vibration?

FYI - We turned my converter as well and it just moved where the vibration occurred in the RPM band. It moved from 1800-2000 to 1600-1800. The over 2500 was still there.

maddboost

iTrader: (11)

Yea they rotated the converter on my car and it didnt help but push the vibration up the RPM band. I guess I will have them try and see if they can run it with the converter pulled out. Man this car is such a pain in the ***. Im gonna get it fixed and sell it for a 330CI.

CrimeSScene

iTrader: (9)

I'm just putting in an M6. Maybe that will help, Maybe it won't. The only thing that I can think of besides the engine being out of balance, is a warped flexplate, which entirely possible on my engine, due to the fact that the dealership has had it out before and I didn't watch their every move. I don't trust those bastards as far as I can kick them.

RevGTO

iTrader: (12)

Tony, I'd appreciate seeing that article - without having to go buy a Hot Rod. CamaroSSdotocm, Rockit, Madboost: I don't know that you'll want to keep this thread going forever, so please PM as your research continues and especially if you find solutions. BTW, since my last post, new wheels and tires and the same vibration in third about 2100rpm. I'm especially interested if an M6 conversion affects it.

PSU_Engineer

Sorry Rev and everyone else, got lazy last night and forgot to write it up. I'll do it tonight.
Maddboost: If you prefer, I will refrain from posting anymore to this thread.

OBXMarine

iTrader: (2)

Not sure if I'm thinking along the same lines here, but from what I've seen/heard, if the TC isn't fuly seated/engaged (During install, it will slide in 3 times), you'll pick up this shudder, I think some fluid will be leaking out too. Along those lines, you may need to place a washer between the TC and flexplate to give it a bit more contact to the tranny shaft.

Just trying to help...

Rockit_GTO

I put in a call to ATI to see if a dampener/balancer might help, but since those are more for High RPM situations not sure.

Like I said before, if we had not pulled the converter off and got the same vibration, I would be more likely to blame the install, the converter, or the flexplate.

PSU_Engineer

Here is that article that I promised you all. I hope it helps someone out.
I think you may be sending (reader) on the wrong track in your vibration concern on his 88 IROC. ("Driveshaft Vibration" Pit Stop Oct 03). He supplied you with clues that point more toward the trasmission as the culprit rather than the driveshaft or rearend. First, he states that the vibration is not present in Third gear at the same speed. Second he states that the vibration is not present in Neutral at the same speed. This is a very important check in diagnosing a speed-related vibration. You can generally eliminate a driveline vibration with this test. A tire/wheel/propshaft vibration that occurs at a given speed will resonate under accel or decel. If the vibration is present in Neutral when coasting down through a given speed, you can usually eliminate these items.
That is why I beleive that he has a fault in the reaction planetary gearset in his transmission. When his trans is placed in Neutral, the drive wheels are turning the axles, differential, and driveshaft. In turn, the transmission is in Third gear, there is no gear reduction through the transmission, giving a 1:1 ratio, meaning that the reaction and input planetary gearsets are all turning at the same speed.
(reader) primarily feesl the vibration under load in fourth gear. since we've already eliminated the input planetary (as the vibration doesn't occur in Neutral), this leaves the operation of the reaction planetary gearset as the probable source of the problem. The fact that (reader) also said that he heard a faint "beating" sound in second gear at 2700 rpm only reinforces this belief, as the reaction Sun gear is held in both Second and Fourth gear by the 2-4 band. As for why (reader) didn't encounter the problem before he switched rearend gears: Most probably, he simply moved the peak resonance of the vibration to a point at which it was more noticeable.
Scott Wagner
Service Technician, ASE Master Technician, GM World Class Technician
Michael Chevrolet
Summerville, SC
Hot Rod Magazine, May 2004 pp106

RevGTO

iTrader: (12)

Thanks, PSU ... as far as I'm concerned, mine feels internal to the powertrain. Although I don't know enough about automatic transmissions to fully understand his analysis, I can can see how an internal imbalance could cause what I'm experiencing. Thanks again.

CrimeSScene

iTrader: (9)

Hate to bring this thread back from the dead, but I know a couple of people might want to know that I finally switched to a M6 and my vibration is totally gone. My converter seems to have been the culprit, but I will be sending it back to Precision Industries shortly to have this verified.

Type_O_Negative_1320

I've been having the same vibration issues for almost a year now with my Vigilante 2800 on my LT1. It sounds the same as most of yours...vibrates a bit in 1st, 2nd, and 4th, but it's very pronounced in 3rd around 2000-2500 RPMs, then again up higher in the RPM range (probably around 5000+). I have a Prothane poly transmission mount instead of a rubber one...while this may be making the vibrations worse, I'd like to figure out what the true problem is and get that fixed. Things I've tried already:

1. Freshly built motor with balanced rotating assembly...I know this is not the problem. I had the same vibration with my 383 that I do with the 385.

2. New flexplate. I scrapped the stock flexplate and installed a TCI SFI flexplate...that didn't fix it either.

3. Transmission rebuild...my mechanic went through the whole thing (long story on how it broke) and replaced everything that was screwed. The vibration was still there afterwards.

4. Spun the converter to different bolt holes...didn't help at all.

5. Switched from 3.42 to 3.73 gears and installed a new posi...this didn't fix it either, although it seems like it made it a bit worse.

6. It's not the torque arm mount...I have a Jegster torque arm and this vibration was never a problem until I got the Vigilante. I had a couple of crappy TransStar converters prior to this one (2400 and 3000 stalls) and neither of them vibrated like this. Then again, they were 12 inch converters and the Vigilante is a 10 inch, so maybe that makes a difference.

I'd like to hear more about the washers in between the flexplate and the converter. Has anyone tried this, and has it worked out? I get a "clunk" noise on 1-2 upshifts and 2-1 downshifts, so I'm wondering if the converter isn't back far enough on the input shaft or something.