This engine bal. has been beaten to death on the 6 speed cars but seems to have died down lately.

Here is my take on it. LS1 engines are EXTERNALLY balanced. This does not meen someone balances the engine externally. it meens the flywheel and PP or TC are out of balance to compensate for internal out of balance. The shop that balanced my Z06 clutch told me that when GM went to the 1 piece rear main seal there was not enough room on the crank counterbalance to balance the engine so they used the flywhhel assy. to balance it.

When we spun up the flywheel by itself it was out by 28 grams. We then installed the PP on the flywheel and the assy. unit was out 14 grams. This 14 grams seems to be the magic number. He then UNBALANCED the new Z06 assy. by 14 grams and it is silky smooth. I feel the Z06 assy. are not balanced the same as the C5 assy. as there are internal engine differences. I sure most all of this applies to the TC assy. as well.

I feel 100% sure if someone spins up a stock flywheel/TC it will NOT be zero balanced.

On the 6 speed flywheel there are many holes on the outer edge that GM uses to instal small balancing plugs to fine tune the balance before the assy. leaves Canada, and I assume the auto's are the same.

At the machine shop they had an old 427 flywheel that had a manufactured in balance weight as big as a small cell phone.

I would be very interested to see the results of someone spinning a flywheel/TC up and check it. I will bet on 14 grams plus maybe a gram or 2 in balancing plugs.

Good luck to you all..

 

I have a vibe from 3800-4000 rpm after installing a Vigilante 2800. To try and get rid of it I took the converter back out and took it to a local shop and had the balance check on it. It was a little off, not enough to give the vibe (I was told). I had it zero balanced internal and external and after the re-install the vibe was still there. I even installed the stock converter back in and the vibe almost completely went away. I thought I'd try my luck again and installed the Vigilante and the vibe was back!

I have even spun the TC 120 deg at a time to see if that would help....It didn't.

I did find out that Chevy balances the engine/ driveline by adding weights to the flex plate, not the flywheel. My car has 2 weights added, they are dime diameter slug that are about an 1/8th inch thick spot welded to the flex plate. I have wanted to pop them off to see if the vibe goes away. I just don't have the ***** to do it though. I'm not sure if the balancing includes the TC installed. If that was the case the stock TC might not have been zero balanced.

There are enough people posting here with different TCs and vibs at nearly the same RPMs that this isn't a problem with one brand.

 

hmmmmm... very interesting

 

Interesting indeed....So, then how the hell can we get these things balanced properly? If this is a common problem with a TC replacement (and it appears it can be), how does one go about fixing the problem. Mine, for example, was done a the stealership....(I know this doesn't mean much) but you would think that this would be a "known problem" and that there would be a process in place to get things balanced properly before the car was returned to the customer. Am I to understand that it possibley needs to be on a dyno to be externally balanced? How would this be accomplished and what kind of shop would do it?

 

Again this is my take............. If you use stock GM parts you have nothing to worry about, because they are already UNBALANCED.....

If you use aftermarket you are on your own....

I agree 110% with you that should be known by anyone in the business because this is not rocket science, it is a very basic thing that should be known by anyone in the business. I can not believe how many people, let alone some very good tuners are unaware of this.
Anyway I still hope someone with an auto will spin up an assy. My educated guess is as before !!!!!!!! NOT ZERO BALANCED!!!!!!!!!

 

the more I read here the closer I am getting to have the factory TC put back on before any damage occurs.

 

Thanks C6 Z06. In my case, the previous owner had this done and I am assuming that they replaced the stock TC with a rebuilt stock TC, because there was internal damage to the transmission when it stopped working. I just looked at the paperwork, and the TC was replaced. But I still have the vibration and I know this is a bone stock setup. But there has to be many others that have replaced their TC with a Yank or other brand that have not had this issue crop up. Thanks for the input.

 

I have to agree with "Didntsettle98"... it is way to coincidental that diff manufacturers are having the same problem with vibration at same rpm. If what some have posted is true then if the factory balances the the whole unit(torque tube,engine,tc,fw etc) as one then when it comes to a warrenty repair at the dealer, the new part..which ever part it may be..would most likely not be the same exact weight as the replaced part and then every part that is replaced would cause this vibration!!!
I have been to the factory in St Catherines ontario and the engine is neutral balanced all other parts are balanced seperatly...this only makes good engineering and manufactuing logic...that way any component externaly replaced would be a straight swap as long as the balance of that unit was NEUTRAL. There has got to be a different answer here.... with all the contacts that this forum has including MR MERCURY, can we not come up with an answer from GM!!!!
PS. If as was stated previously about the factory balancing the whole assembly together was true... then you would have had to mark the splines at the crank to match the splines on the drive shaft as well as have the crank coupler in the exact same possition, and mark the fact TC on the flex plate in order to install It in the right holes to be at the exact same balance before dissassembly. The odds that some who replaced their stock converter back in and got this exactly right without marking them are astronomical... THERE HAS GOT TO BE ANOTHER ANSWER HERE.... it has got to be the sequence of the re/re.. I hope someone threads in with the solution!??? greatly appreciated for all the input.

 

Ok I reclocked mine and it fixed the Vibration. Smooth as silk. It was a minor Vib at higher engine loads. I also wonder if it was a torqueing issue on the bolts.

 

SAME EXACT Dang problem here.....mine as been at dealership for SEVEN WEEKS and no fix yet!!!!!!!!

 

still no answers... come on guys, where are the techs from gm. I talked to carmen at Vette DR and he seems to think its the converter... I'm not sold on this yet, tooo many coincedences from to many manufacturers and right at the same rpm.!!! i'm hoping.....someone????

 

whats the correct torque for the bolts on the converter

 

i have been to the corvette engine factory in canada and they only balance the 6 speed engines after assy.

 

Clem, do you have any idea why they only balance the 6 speed engines??? I follow this engine balancing thing as kind of a hobby..

This thing has been discussed for ever and as I said before this is not rocket science.....

These things are either ZERO balanced or NOT, it is exactally that simple....

I still vote for NOT zero balanced but it would not be the first time I have been wrong....

Good luck to all that have this problem

And good luck to all our troops.......

 

my guess is because the large diameter if the flywheel vs the hookup for the A-4 on the engines. just a guess,the farther out from the center the out of balance is located the more effect it has.

 

my new protorque 300 has the same annoying vibe, i hope we figure it out

 

 

Interesting. I found this post by ArKay99 over in C5 General. A guys car has been at the dealer for 7 weeks trying to find a vibration. I'd be willing to bet that at least in my case, this could be what is causing my vibration. I am not hopeful that this will ever get fixed.


"Sorry to hear about your troubles. Here is my take on what possibly went wrong. When changing the TC the flexplate was probably removed. It states in the manual that you have to mark the location of the flexplate when removing it. This is because sometimes after the initial engine balance the balance needs to be tweaked on the assembly line. Some engines require it, some don't. If the flexplate was offset balanced to correct for an engine imbalance and removed and not put back on in the exact position it was removed in, you will have vibration. OR, they put in a new flexplate that wasn't balanced, OR that flexplate needs to be offset balanced exactly as the original was. However, if the original wasn't marked there will be now way to know where to drill the offset hole. There is a way to balance it afterwards, but it involves using a strobe light with the inspection cover off. I have never seen this done but there was a member about a year ago that had the dealer replace his clutch and flywheel and they messed up the same way by not marking it. The end result was GM sent 4 engineers to the dealership and they used that strobe light method to pinpoint the heavy spot and balanced the assembly that way. This might be your only solution. Time to start spanking some butt and getting some help from higher places. BTW, there is another way to do it but I've only heard it done on manual xmissions. You have to use washers and trial and error under the flywheel bolts, but I don't know if this method could or should, be used in your case."

 

So it is possible that this problem can't be fixed if they did not mark the flex plate. Is the solution to sell the car????

 

I don't think I am going to sell my car because of this, because the vibration is only at the 3500rpm band and I don't drive it there much. But it appears that to fix it is tricky to difficult at best. But the bottom line for me?...I have no clue .....whatsoever. I don't know who to take it to, or if there are any places that even have the capability to diagnose and check balance....at least in the Seattle/Tacoma area. I guess if it breaks, it breaks, and I'll deal with it then. I just can't worry about it any more.