For the torque tube to be causing the vibration/rattle, wouldn't the car need to be moving? Movement is not necessary for the noise, just 850-900 rpms.

 

Retired GM engineer says these harmonic dampeners are used to absorb noise that may be transferred to and end point(in this case the rear end). He said they are used on many cars to absorb harmonic vibration.

 

You seem pretty dead set on that being the problem, so why are you even here? Why are you asking us? Were you actually looking for advice or just affirmation? If you're so confident then replace the f**king thing and see for yourself. But I'll say it again, that dampener has no moving parts. It's a lump of metal. So provided it's still in one piece and still securely fastened to the differential you can move your witch hunt to another location.

You've received a lot of good advice, but it does not appear that you're going to take any of it. Pulling the AC belt off would take all of 5 minutes, and that would tell you really quickly whether or not it is actually related to the AC.

REALLY hard to help those that won't help themselves

 

no, not in an automatic

(retired GM engineer didn't realize this?)

 

OK here we go again. The car is 13 years old and you bought it used? How many miles on her? Like I've said in previous post any C5 that has 100k miles or 13 + years old will have bad torque tube couplers. This is just a something that will have to be replaced on EVERY C5 sooner or later. I learned this the hard way .

 

I would not modify/remove the rear damper. It is a designed unit to offset the natural frequency of the rear end from the frequency/vibration from the engine/driveline. These engine frequencies/vibrations are normally strongest in the 700-900 rpm range and this is pretty normal across different engines. Saab even makes a special two piece flywheel with springs and lubricant inside to help reduce the vibration input to their drivetrain. Because the C5 engine is bolted to the rear with the torque tube, this aspect/issue has to be addressed and it done by offsetting the rear end natural frequency to reduce resonant vibration. Something is wrong to cause the vibration you are having. This something needs to be found and fixed.

I really don't want to jump directly into the torque tube yet, but I am leaning that way. If I have read the posts correctly it does NOT do it in neutral but does it in gear. If this is the case and being an automatic, in neutral the driveline is rotating, but not loaded (finding strong resistance) at the transmission/rear end. In gear, it is loaded at the rear and any torque tube issues would be increased.

If it is not being caused by the A/C (remove belt to test), then it may very well be the torque tube couplers. Maybe the torque converter but couplers more likely. If you go into the tube you could replace or have the converter tested.

Has anyone had motor mount problems? Possibily a broken insulator could also cause this. I could make a case it might. Looking under the hood and having someone rev the motor could remove or affirm it is an issue. Looking for excessive motion/motor rotation.

 

Helped a buddy yesterday with a 2000 Auto Coupe with 150,000 miles. He had a KNOCKING NOISE when in gear. He was told it could be a cracked flex plate so, he wanted to change it.

That requires complete drivetrain removal.. So,, while we had the drivetrain out, I poped open the Torque tube just to check it out and LOW AND BEHOLD, the damn couplers looked horrible. They were cracked and chunks of rubber were missing in areas around the bolted areas of the coupler. Needless to say, we have new Gublios on order from Autozone..
DORMAN now make the couplers and can be had for around $55 each!!! Learned a LOT yesterday!

So glad that we opened up the Torque Tube. Most likely the problem the whole time! We did not find the flex plate cracked but some of the bolts that hold the plate together were slightly loose.

BC

On a side note,, We visited Chuck at Corvettes Of Westchester to see if he had any couplers that he could sell us. He had a set BUT,,,, they were for late modle torque tubes. The 97-2000 use smaller couplers and the 2001-2004 use a thicker coupler. The late modle wont fit early modle TT..

Chuck had THREE damaged torque tubes that we opened up to see if we could use those couplers. They all had less than 100,000 miles on them so he was willing to let us have them. Each TT that he opened had deteroriated /damaged couplers.

Chuck showed us a couple repair procedures to allow us trouble free reassembly when the new couplers arrived! What we learned will help us get the couplers installed 100% correct.


Thank you Chuck for helping us and allowing us to use your knowledge!!

 

Once the car is on the rack, how much time(by a qualified mechanic) to remove torque tube and inspect the couplers?