I'm in a middle of trying to find a source for heavy vibration at 3500 rpm. The car is a C5 ´99 and when it came to me it had tranny (Goodwrench unit), torque converter and balancer replaced. Unfortunately the history of the vibration is unknown but the balancer was replaced because of that.

Because it's a C5 and the torque tube makes the drive shaft rotate along with the engine no matter what you do, I started by looking inside the TT. The guibos were bad but not as bad as I expected. I replaced those with new AC Delco units and put the whole thing back together. The vibration was there as before.

I took everything apart again and took the drive shaft, torque converter and it's flexplate to a machining shop to be balanced.

The drive shaft was good as it is. The flexplate had already 2 small weights in it and it was also in balance.

The torque converter is causing some headache: First it shows 0.31 oz imbalance. When the rotating continues a while, it climbs to 1.72 oz and stays there. We thought the remaining oil inside the TC is causing this and I have been trying to get it all out but with no luck. There seems always be a little remaining inside.
We of course made a pilot which centers the moving parts inside the TC before balancing.

Could it be that the remaining oil makes the balancing impossible or do I have a bad converter?

The balancing machine is made for drive shaft balancing, not an actual TC balancer.

 

You are going to need to send the torque converter to a transmission/ converter shop.

The torque converter will need to cut and cleaned out before anything else.

Good luck

 

You are going to have a VERY difficult time accurately balancing a converter with fluid in it. To properly balance a converter it has to be dry and the interials held stationary(custom splined shafts) and on center (bushings to accompany aforementioned shaft).

 

Thanks for replies this far.

I called to machine shop today and asked where we are now. They said they have got 7 oz of fluid out of the TC. We agreed they will test the balance once again and if the imbalance is again that 1.72 oz and in the same position, we will put that 1.72 oz extra weight to compensate that.
If the result is something different from that 1.72 oz, we have to discard the TC and start claiming process to the seller.
If the TC would be the 100% sure cause for the vibration, this would be easy. Now that I don't know exactly which part is causing it, I really need to find a faulty part before I put everything back together. With C5 the disassembly and re-assembly takes so much effort that you don't want to do it many times just to check one part at a time.