I recently replaced my clutch, flywheel, and pressure plate, while my T5 was out of the car. Since then, I have had a severe engine vibration at around 3100 RPM that shakes the entire car. It will do this in neutral, in gear, moving, or stationary, clutch in, or clutch out. My replacement flywheel was identical to the one I took out, including the balance weight in the casting. I replaced my harmonic balancer, which wasn't in very good condition, and that did not solve the problem. For now, I am working under the assumption that there is nothing inherently wrong with the hardware I installed. It was mentioned on the transmissions board(I originally thought this was related to my T5 rebuild) that replacement flywheels are supposed to be balanced with the engine after installation by the trial and error process of adding weights to holes in the outer perimeter of the flywheel until all vibration is eliminated. I can't seem to find any further instructions about this procedure or a source for weights. Can anyone share there experiences with this process?

 

Not true. The weight on the flywheel is a "spec" value, which doesn't change from engine to engine.

If your engine was balanced by altering your previous flywheel, then whoever did that should be shot (after they fix it, of course).

I would have to conclude that there is something inherently wrong with the hardware you installed (assuming the above paragraph was not the case).

 

Don't forget the clutch cover (AKA pressure plate). Most out-of-balance are this and not the flywheel. Vibrates exactly as described.
All flywheels are balanced at "birth". Cheap clutch covers are a different matter...
Run the engine with the flywheel and clutch cover at 3k and then with just the flywheel; if the vibration is gone don't be surprised.

 

Well, rather than prolong the inevitable, I sucked it up and took the flywheel, clutch, and pressure plate out of my engine tonight. They will be sent over to a reuptable machine shop to be balanced to spec as an assembly, or however they choose to do it so that it does not vibrate anymore.

It makes me wonder from where is material added/removed from a pressure plate to balance it? I'll report the results when I receive them. Hopefully I'll be on the road by memorial day. At the very least, I set a personal record for dropping a tranny.

 

Well, the machine shop refused to believe that the flywheel I brought in was for a 305. He said the only engines that got the weight on the flywheel were the 400's. I believe this is wrong, but couldn't convince him. So I still don't know if my flywheel is bad. Not sure what to do next.

I know the engine was rebuilt prior to me buying the car. According to my parts sources, the TBI engines of this year had a flywheel without the additional balance weight. Does anyone know the reason for this? I'm wondering if when my engine was rebuilt (prior to me purchasing the car) a some part of a TBI assembly was installed to not require the weight.

To complicate things more, the flywheel i pulled out of the engine had the weight on it, but i got rid of it so have no comparison with the one I have in there now aside from the fact that I know the additional weight was on there. Perhaps they took weight out of the TPI flywheel to get it to work (ie a bad job and lots of holes)

Anyways, from the people i've talked to, they think it is unlikely that the new flywheel is out of balance from the factory.

I guess my next 2 options are to try another flywheel with the weight on it (on the off chance that mine is bad)
OR
Try my luck with a neutral balanced flywheel.

 

Here are the instructions from the '92 Camaro FSM on V8 flywheel balancing (as pic's). If you really have some time to kill drop this in google:

+flywheel +spec site:www.thirdgen.org

As for flywheels/flexplates on 1-piece RMS SBC's. They have a counter weight to make up for the loss of the crank weight. The flywheel/flexplate is NOT neutral balanced. They have a dog-bone to make up for the loss of the dog-bone on the end of the crank. Simple as that.

What I don't understand is why this isn't spec'd and taken account of when a flywheel/flexplate is built. But it is this way, the flywheel is rough balanced. And needs to be fine balanced on the engine.

RBob.

 

This probably isn't your situation but I've seen people with a 400 SBC (externally balanced) lose the dowel pin out of the crankshaft. When reinstalling the flywheel, it will go on in any position. If the dowel hole wasn't lined up to where the dowel was, it would cause a severe imbalance.

I know it might be a pain but to test if it's the clutch or the flywheel, pull the tranny and clutch. Leave the flywheel attached and fire up the engine. If it still has a vibration, the problem is with the flywheel.

Stepping on the clutch just disengages the tranny. The pressure plate is still spinning around with the flywheel.

Did you install a new pilot bearing?

 

Id say that its your pressure plate if its a reman cheapo. And you can tell your guy at the machine shop that a 400 flywheel wont fit a new model center bolt motor cause the cranks bolt to the flywheel differantly. They dont make 400s that have that bolt pattern.

 

are you sure you put your driveshaft back on the same way it came off and that the weights are not missing on it when i pull a trans out i always mark the drive shaft and the yoke of the rear end

 

Driveshaft isn't spinning when the car is stationary. It's strictly an engine rpm vibration.

 

Problem solved:

Since the problem was either in the flywheel or clutch, I decided to bring both of them back under warranty, claming they were out of balance.

I took the refund and switched brands. The original flywheel I put in was an LUK. When I compared this one to the Standard brand flywheel i bought (which is an original, but resurfaced GM flywheel) I could clearly see that this was my problem. The LUK had a lot of machining done on the cast balance weight, as well as many large holes drilled to further reduce weight for balance. It looked like a hack-job compared to the new part. The GM flywheel had a minimal amount of machining and additional balance weights added to the appropriate holes in the flywheel, definitely better quality.

Also, when comparing pressure plate designs, the LUK pressure plate was inferior. The housing looked like it could have easily been out of balance, the spring was weak, and the area that contacts the clutch disk was very thin and light. Also, since I had the chance to drive the car with both the LUK and new clutch, I was able to tell comparatively that the LUK clutch disk had very little grip, and engagement was not a positive experience (kind of felt like the disk was made of gel)

In any case, I definitely learned a lot about sourcing auto parts, and to sum up the experience: don't use any LUK clutch components, or whatever else they make.

 

Good to hear that it worked out. By the looks of it the LUK people tried and totally messed up balancing that flywheel. And the 'pre-owned' GM flywheel had a decent balance on it already.

I've had my fair share (or more) of vehicle vibration issues over the years. So I know how frustrating it can be to get it sorted out.

RBob.

 

Whoops .. wrong thread.

 

[QUOTE=91FirebirdFmla;4166561]Well, the machine shop refused to believe that the flywheel I brought in was for a 305. He said the only engines that got the weight on the flywheel were the 400's. I believe this is wrong, but couldn't convince him. So I still don't know if my flywheel is bad. Not sure what to do next.

I know the engine was rebuilt prior to me buying the car. According to my parts sources, the TBI engines of this year had a flywheel without the additional balance weight. Does anyone know the reason for this? I'm wondering if when my engine was rebuilt (prior to me purchasing the car) a some part of a TBI assembly was installed to not require the weight.

To complicate things more, the flywheel i pulled out of the engine had the weight on it, but i got rid of it so have no comparison with the one I have in there now aside from the fact that I know the additional weight was on there. Perhaps they took weight out of the TPI flywheel to get it to work (ie a bad job and lots of holes)

Anyways, from the people i've talked to, they think it is unlikely that the new flywheel is out of balance from the factory.

I guess my next 2 options are to try another flywheel with the weight on it (on the off chance that mine is bad)
OR
Try my luck with a neutral balanced flywheel.[/QUOTE

i know this is old but if you had an external balanced rotating assembly you need to install one with a counter weight. ]

 

Not all 1 pc rms engines are externally balanced, externally balanced only means that when the crank is balanced on the balancer that the harmonic balancer, crankshaft, Bob weights, flywheel, pressure plate or flex plate is installed during the balancing procedure.
If it neutral balanced you do the crankshaft and Bob weight together and the other components separately. Most clutch manufacturers tell you to check these like McLeod.

 

Driveshafts are balanced both static and dynamically off of the car
So same position is highly likely to not be the issue or an issue. Glad the poster got this figured out, manufactures screw customers a lot. I’m about to install a Ram conversion clutch for my T56 swap, they claim it’s all balanced but I’m going to check before I take anyone’s word for it.