Part 2-

The torque tube driveshaft rides inside the torque tube and spins at engine RPMs. The front of the driveshaft is connected to the splined input shaft via the rubber/fiber couplers, the splined input shaft connects to the flex plate, the other end of the splined shaft rides in the torque tube on the front 6007 bearing. The other end of the drive shaft is connected to the output shaft via the coupler, the output shaft rides on two 6008 bearings inside the rear bearing carrier housing, the rear bearing housing rides inside the torque tube. All of the shafts, input, output and driveshaft have a tri-lobe flange with three 12mm bolts sandwiching the couplers between the flanges. In total there are 4 tri-lobe flanges, two couplers, 3 bearings, 3 shafts and the rear bearing housing all riding inside the torque tube.

In a perfect world you would expect all of the 3 shafts to spin on a single centerline axis, all of the flanges square with each other with ZERO runout and perfect balance, but that would be an unrealistic expectation, that’s why we have tolerances. When I set the complete driveshaft with bearings on V-blocks and used dial indicators to measure runout I was very disappointed. A realistic runout tolerance would be .005 or less, I measured .009 to .022 runout on the two driveshafts. I’ll call the high side 0 degrees, on the first driveshaft assembly on one end the runout was +.016 and center was +.016 on the other end it was MINUS - .009, on the flanged tri-lobe yoke at 180 degrees it was +.015, the rear carrier housing was tilting -.009 with the high side, WTF. At first I tried clocking the connections trying to find the sweet spot, but it was futile. So basically, the driveshaft has 3 centerlines and was orbiting and wabbling around the true center line axis. With that again I’m very disappointed, I think I’m going to have a custom high precision 3.5” shaft made and delete the couplers.

Stay tuned for part 3, I’m going measure and scrutinize the input and output shafts without the bearings along with the rear bearing carrier housing.
Comments and Critiques welcomed.

 

Is there any evidence of balancing weights having been applied to the shaft (like one typically does on conventional driveshafts)?

 

You have really examined this torque tube, I compliment you! I note you have solid couplers installed, which is going to exacerbate any minor runout or factory misalignment (which is going to happen since these parts are not aerospace). The rubber couplings help tame those manufacturing irregularities and mute any resulting vibration.

I will say, your findings in Part 1 regarding the bearing seating surfaces are fanatastic and much appreciated. I look forward to real world testing with the low deflection o-rings.

 

Looking at your pictures more closely, I do see at least two "bolt-on" weights (?) at the ends of the tubes -- are those balancing weights? Are the dimensions of the internal tunnel so tight that the weights can only be placed where the tubes neck down a lot?

Yeah, that red solid coupler is very odd -- aftermarket, I presume?

 

Balancing weights are there on the yoke

 

Thank you,
The solid couplers were installed in the original car at some point, I bought both of these torque tubes off of Ebay, both are from a Z06. I agree that the solid couplers would make noise and vibrations more apparent and I would not use them on a shaft with this much runout . If I get a driveshaft made and the runout was .005 or less I would consider using the solid couplers, or just delete the couplers. For now I'm just finding the problem areas, documenting, sharing, then I will decide if I could correct the problems or have a shaft made.

 

The original driveshaft tube diameter is about 2.750". A few shops who make driveshafts make a 3" and a 3.5 inch so there is room, likely the put the weights on the yoke because its solid and the tube wall thickness is .125 or less so drilling a hole for the weight would compromise it's strength.

 

Thank you for the work and time you're putting into this. I find it intriguing and very helpful especially if I need this repair down the road.

 

And thank you also for the comments. Is your vette auto or manual? How Many miles? Do you drive hard or put it on the track? Have you ever had to do the torque yet?
Be aware and keep on the look out for new noises and vibrations developing and if you suspect a problem don't ignore it because it will likely happen but I hope not.

 

Mine is a 2016 Z51 with a manual and 47K miles - most of those clocked by two previous owners. I haven't done the torque tube nor did the car come with any documentation relating to any rebuild or replacement of the TT. Fortunately, it's not displaying any of the common signs of failure or excessive wear. I've read on the forum some have had issues and I like educating myself about it. If it were to need rebuild or clutch service down the road, I would likely do it myself and the information you're providing is very in-depth and helpful.

 

I just noticed that you are in Phoenix, so am I in Ahwatukee. I'm thinking about buying a few torque tubes off ebay, rebuild them and sell them ready to install, because it seems that OEM support and new parts are waning. Also some local shop who used to do torque tubes stopped doing them due to lack of OEM parts.

 

So OEM support is thinning on the last generation car already? As a C5 owner, I am used to it, but I am looking to a C7 as an upgrade and to not have lack of new OEM parts and support.

 

I had a C5 also, 85,000 trouble free miles until I crashed it, I did a flat spin clockwise then another flat spin counter clockwise when I cranked the wheel hard left and was spit out from underneath a 18 wheeler trailer. The C7 is a great car so don't let the torque tube issue keep you from getting one.

 

Once upon a time LG racing had carbon fiber drive shafts available might want to give them a call

 

I think I'm going to get driveshaft shop 3" aluminum

 

I am in Phoenix also and had a torque tube go bye bye. What is the average run out you have found on the other ones you have rebuilt? Where did you find the bearings at for a rebuild? Debating on going with the aluminum couplers since the rubber doesn't like higher hp.

 

My first experience with the C7 or any torque tube was about 7-8 months ago when mine went bad, was rebuilt and now bad again. Now with my TT round 2 I decided to get to the TRUE Root Cause of these failures, so I bought 2 TT off ebay to take apart and analyze. Of the two driveshafts I've measured from left-center-right side one was +.016 +.016 then a minus -.009 the other was +.015 +.022 +.009 this was on the tube, then on the yokes were from +.007 to +.015. Looking at the pictures I posted it's important to notice the longer straight line that marks where high spot is, when the lines are not lined up means the center line at that point on those parts both have different centerlines and both have different centerlines from true center. With the high amount of runout the solid couplers will transmitte the vibrations and noise more, on the flip side the rubber couplers will flex and absorb the excessive runout but all of that flexing creates friction and heat within the rubber coupler causing it to fail.

I ordered the bearings from Amazon, they are standard NTN 6007 and 6008 bearings with the LLB suffix indicating non-contact zero drag seals. The O-rings Amazon also are Viton 2.5x63 and 2.5 x 68. Be sure to look at part 1 I posted earlier.

 

Being such a massive "Design Failure", why is this not a Safety or Operability recall?

I have been hearing the noise, but thought it was just a loose piece of heat shield or exhaust somewhere.

I have since found out I was horribly wrong.

Here are pictures of my TT.

I just can't believe the National Automakers don't recall this systemic C7 issue.

Anyone here know why or if there is a recall?

When I Google That $hit (GTS), I get this statement:
The National Highway Traffic Safety Administration (NHTSA) issued a service bulletin for the C7 Corvette's torque tube, which states that the torque tube can be difficult to align when reinstalling it. The bulletin also provides the following guidance:

• Avoid using bell housing attachment bolts
  Do not use the bell housing attachment bolts to tighten the torque tube against the bell housing.
• Misalignment can cause issues
  A small amount of misalignment can cause the propeller shaft's input splines to catch on the crankshaft, which can wear out the crankshaft thrust bearing. If the engine is started in this condition, it may require an engine replacement.

This only addresses difficulty in alignment. WTF?

I would love the here from people more knowledgable on htis TT issue.

Thank you.

 

Part 3 & summary posted.

 

Have you rebuilt it yet?