elesquan

iTrader: (1)

This is a snow balling, never ending, PITA!
A few weeks ago the rear end blew up on my way to work. Pinion out the bottom of the housing. This happened while accelerating at maybe 50% throttle and I was up to around 50 MPH when it blew up.
Replace the rear axle assembly. Then test drove and it felt like the trans had some major damage. Removed trans (T56) and looked over the clutch not seeing any damage I tore down trans. Nothing inside would have caused issue, so removed clutch and eventually found the disc was broken inside the spring hub assembly.
Fixed some issues in trans while it was apart, replaced clutch disc only, reusing PP and flywheel.
Now back on the road again, but has a vibration around 2200 to 2800 RPM that was not there before the rear end blew up.
This is consistent, and is there regardless if the car is moving, revving engine with clutch pressed in, or with trans in neutral.

Mostly stock LS1 engine, 110,000 miles on it.

Does the vibration damper on these LS1 engines have weights to help balance the engine?
I was wondering if maybe the damper could have anything to do with this new vibration?

The vibration is not so bad that feels like it is coming apart, but bad enough I do not dare stand in the throttle anymore..

Any thoughts on what else I messed up?

JakeFusion

iTrader: (7)

You reused your pressure plate? Was it ok? What about the flywheel? If either of those are damaged, you'll have vibration.

elesquan

iTrader: (1)

I had the flywheel resurfaced, the PP did not look bad at all, and did not notice anything damaged. The PP is the LS1/LS6 SAC, and I reset the adjustment back on it with the press method I found here on LS1TECH. Nothing seemed bad with it, but I did tear down the trans when the clutch disc was the issue, so overlooking something with the flywheel and PP is a real possibility.
Thanks for the reply.

john j oliver

iTrader: (4)

Read in a mag a while back about a vibration issue that drove them crazy. It turn out it was a bad axle replacement. Not saying that this is your problem but more of an fyi. Put a dial indicator on the axle plate (where the wheel studs are) and measure the run out. Takes a few minutes to do with no cost.

john j oliver

iTrader: (4)

On further reading, seems like you should centralize on the trans clutch and flywheel.

ls1 1990 VN

Unbalanced clutch issue!

gagliano7

RockinWs6

Probably the easiest way to solve this is to pull the trans and PP and run the engine.

Exidous

iTrader: (11)

Since it does it when the car is not moving it is something with the flywheel pp or disk. The trans in neutral only has the input shaft and countershaft spinning. They don't really have enough mass to cause a lot of vibration.

What if you put the trans in gear and rev it with the clutch pedal to the floor? If it still vibrates it's the PP or flywheel. That eliminates the disk.

elesquan

iTrader: (1)

Thanks for all the replies!

The vibration is still there when stopped, clutch disengaged and transmission in gear.
So it would eliminate the disc and transmission from being the source.
It is unlikely that anything happened to the flywheel in my opinion because what could go wrong? The clutch engages very smoothly, and it did not take much to surface it, so I doubt it is warped or something like that.

That leaves the PP, or internal engine parts, or the harmonic balancer, or the belt driven parts.

I assume from the replies (no one has suspected it) that the balancer must be neutral balanced, and would not be the source?
Watching the balancer while engine is idling it does have a very small wobble to it.

I would think that if I ignored the problem the result could be engine bearing damage.
Right now I am driving the car 15 miles or so a day but mostly keeping the RPM's under 2200 until I figure it out.

Thanks again,
Bruce

Exidous

iTrader: (11)

I always thought the balancer was internally balanced with the internals but I could be wrong.

badamn

Yeah the engine should be internally balanced so no need for the balancer….My engine has been doing the same thing (vibration around 2200)ever since a Monster stage 2 install and a trip to the track.Sometimes a little more than others.I figured it might be a clutch thing.I'll try to let everyone know.It will be months away i'm sure.tranny needs to be rebuilt as well.

gagliano7

We put a 383 small block which was in my truck in my friends 77 camaro. In my truck there was no vibration but in his car we had a bad vibration from 2000 rpms and up. Balancaed driveshaft no change , Reved in nuetral no change, disconnected trans no change. Removed pressure plate and clutch vibration was gone. Found the POS Centerforce pressure plate had centrifugal weights on it. Removed weights and everything is fine now.

elesquan

iTrader: (1)

Thanks for all the input.
It sounds like it about has to be the PP.
It is odd that it worked fine before??
Maybe a chunk of the old disc is inside there.

gagliano7

Let us know what you find out.

cool breeze

iTrader: (1)

Find anything out?
Im having the same issue with my ls1/m3. Coincedentally i have a monster stage 2 setup as well…emailed them and said their units are perfectly balanced...

gagliano7

So did centerforce but there weights through the pressure plate out of balance.

LilJayV10

iTrader: (39)

My monster 3.5 vibrated just like that, till I replaced it.

elesquan

iTrader: (1)

So I am not 100% positive I figured out the problem, but I thought through all of the process and remembered that the shop that resurfaced the flywheel were not able to get one of the 2 dowel pins out. They machined it off flush.
The other dowel pin was put back in.
I think that the little bit of extra weight from the complete dowel pin is causing the vibration. I will try to find a different flywheel to use the LS2 type pressure plate and get that installed. Not sure how soon, but I will try to remember to post the results.

xopbartkusu

The trans in neutral only has the input shaft and countershaft spinning.