GreekBoy229

Hello,

I have been a long time viewer, first time poster. Corvette Forum has helped me out a lot in the past from helping me diagnose and repair a bad ignition switch that turned the car off while doing 80mph on the freeway, repair a dimming temperature display, to even providing a how to for me to replace my clutch when my slave cylinder lost a seal. I believe I have developed a new issue that I cannot diagnose and cannot find any other topics on.

Recently my 2001 Z06 (56k miles) has developed a slight stuttering in the rear that feels like there is a binding in the drivetrain. It is not speed dependant and will occur worse if going over undulating pavement, but is even present when going over freshly paved asphalt. Sometimes it will feel like my shocks are blown and goes into a resonance in the rear and won't stop bouncing if I get a stretch of wavey pavement. I brought it to a mechanic that I trust but he couldn't figure it out as it is slight and can be perceived as a stiff suspension. I daily drive the car right now and have noticed the difference. The suspension is never settled, especially around turns where it will get worse. Also, when going over a bump at the end of a driveway, there is a loud rattle and the driveline shakes around.

I originally thought it was a cv joint going bad (had a torn boot that I replaced and regreased when doing my clutch) so I replaced that half shaft. That helped a little, but did not make it go away. So I replaced the other half shaft with no change. Greased the splines while in there and torqued the axle nuts to 120 ft-lbs. I also checked my toe rods and wheel bearings while at it and there is no excess play in the tire side to side or up and down and the bearings are silent and turn smoothly. It was recently aligned too. I then thought it may be my shocks, so I replaced them with Bilstein Sport B8's, and that didn't help either. I took a wrench and checked every bolt on my rear suspension and subframe and it's all tight. I also took a pry bar and checked to make sure I didn't have excess play in my diff bushing and it wouldn't budge. My sway bar end links are not broken and have been updated to metal ones. I also replaced the diff fluid last summer when I did my clutch with Redline and have put about 6k miles on it, so it's fresh. My mechanic also added some extra limited slip additive recently when he was looking at it, and I went and drove figure 8's to work it in, but that didn't help either. So far, nothing I have done has helped. This will occur only when the car is moving, regardless of if it is under load or just cruising, regardless of gear, and regardless of clutch in or out.

I am stumped and am curious if anyone has had a similar issue. If anyone could help out or shed some light it would be greatly appreciated. And sorry for the long post, just trying to be thorough and relay all information.

Thank you,
Greek Boy

Ps- tried to check my motor mounts, in case that's what was causing the shake, and it doesn't appear they have excess movement. Got under the car to look at them visually and it was hard to get a good look, not sure what they are supposed to look like installed. I saw no leaking fluid from them or residue signs. They looked like they may have been cracked through the center, but that may also be the molding parting line from when they were made, so I'm not sure. Couldn't get a good picture either.

GreekBoy229

As I think more about this, does anyone know of a good way to check the differential clutch packs for wear, or do I have to pull it apart to do so? I'm not sure what to check next.

GreekBoy229

8VETTE7, there are no codes being thrown. Nothing on the DIC and nothing on my code reader. Neither traction or stability control kick on unless I actually get the rear tires spinning. I tried turning traction/stability completely off, and also tried competitive driving mode, and it didn't make a difference. Still had a slight bouncing/stuttering in the rear and an unsettled suspension through and coming out of turns.

GreekBoy229

8VETTE7, thank you, I didn't even think of checking BCM or other vehicle codes. I've used the DIC before, I just like using my code reader better because I don't have to write down the code and look up the meaning afterwards. It displays the code and what it stands for right to my phone. It's nothing special, just a Bluetooth interface and the Torque app. I forgot it's only an ECM interface though. Will check the DIC and see if there are any codes I missed.

Bill Curlee

I read your post several times and then I had a brain storm... If it were my car,, I would check the Torque Tube rubber couplers. Sounds just like what happens when start coming apart..

Bill Curlee

Jack up one rear wheel (leave the other one on the ground) Put the trans in "N" and attempt to rotate that raised tire.If the limited slip clutches are working, it will be somewhat difficult to rotate. Brand new clutches and good beleview clutch pack springs break free over 100 ft/lbs. If you get 45-50 ft/lbs, call it good. If its LESS than that,, could be an issue.Then check the other wheel.They should be pretty much equal in break away Tq..If its really light, this could be the cause!

GreekBoy229

8VETTE7, I just checked the DIC and it only had one code, U 1064 H. I looked it up and I believe it is attributed to a column lock issue. I installed a bypass a few weeks ago because mine locked, so not sure if it is a historical code from that or not. I do not believe this is part of my issue though.

GreekBoy229

Bill Curlee, I owe you may thank yous. Your ignition switch rebuild post helped me out tremendously in determining why my motor was cutting out and how to solve it. Your write-up was very easy to follow and I cannot thank you enough for posting it. So I just want to say, thank you.

That being said, you posted the response I was dreading to hear, that it may be the drive shaft couplers. I kick myself for not checking them when I had the drive-train out of the car to replace the the slave cylinder and clutch, I just didn't know better at the time. Pulling the drive line is not an experience I would like to relive, it was difficult on jack stands and I actually broke my nose doing it (a muffler slipped out of its hanger and onto my face). Your posts have me curious though and I have a couple of questions:

1) What are the beginning symptoms of failing drive shaft couplers? I can only find posts of the symptoms right before/after significant failure, where the torque tube itself is already in two or more pieces, or it sounds like it has marbles rattling around in it (mine is currently quiet). I cannot find anything for the symptoms before this point though.

2) Will these symptoms still exist with the clutch pedal pushed down and the transmission in neutral? I still get my stuttering symptoms in this scenario, but as I understand it, there should be no input to the drive-shaft from either the clutch or the transmission in this state. This should keep it from spinning or putting any load into the couplers. Please correct me if I am mistaken.

3) Is there any way to check the torque tube bushings without removing the drive-line? Either a static test loading and unloading the drive-train, or turning the drive-line by hand with a stethoscope against the torque tube? etc?

4) To check the clutch packs in the diff, I am assuming I just put a torque wrench on the spindle nut to check it? Does it matter that I will be spinning the tires opposite directions to check each side?

If I have to pull the driveline again I will, I would just like to be a little more sure that it is the right step to take.

Socko

I have possibly something simmilar. There is definately something sketchy in my driveline. I replaced all the bearings and couplers from my torque tube last year. Got the trans fully rebuilt as it ate some syncro keys. Got a new clutch, master, slave. So i am pretty sure it is a diff. My guess is spider gear related. Either bad clutches or cross pin play or something. I am just planning to run it till it breaks. In my experience with differentials, i have broken and replaced a couple in different cars, sometimes they just make tons of noise. If I chased after every noise my car made, I think I would literally be cheaper off buying a c7 then staying in my c5. lol

When i rebuilt the tube in my 03 last year. It was in perfect condition outside one of the bearings that was clearly bad. Not destroyed mind you, but it wasn't right. Stock couplers are pretty resilient it seems as long as they don't have a ton of miles. My car was at 40k. My friends car at over 600 wheel torque had close to 20k on it when his got done and they looked brand new too.

01silvercoupe

Have you also checked your control arm bushings?

GreekBoy229

Bill,

I finally got to check these this morning. Each side broke free at just over 60 ft-lbs. They each spun smoothly with no perceived chatter. Not sure if this is something to still consider as cause or not.

GreekBoy229

Socko,

If you figure yours out, please let me know. As far as noises go, I learned the same lesson on an '04 GTO I had. I spent a lot of time trying to chase down every rattle and squeak and it drove me nuts. Was bittersweet when I sold it. The vette right now though is silent unless I am going over a driveway. Going down the road it makes no unusual noise, just starts stuttering. The only time it rattles is on a driveway bump, and that shakes the entire car at the same time. If it didn't start shaking while driving, I wouldn't worry about it. Hell, I lived with an annoying constant squeak till about 2 months ago that turned out to be a loose center cap. Noises don't bother me as much, as long as I know they aren't anything serious.

GreekBoy229

Silvercoupe,

I have, nothing is pushed out, torn, or cracked. I got a little more play out of the upper rear control arm bushings on the driver side this morning when checking my diff breakaway torque, but nothing excessive. It was just a little more than the passenger side.

GreekBoy229

So, I am thinking it may be engine mount related. When I first start the car and leave the clutch pushed in so it hasn't engaged the drive shaft yet, I will rev it and watch and feel the motor shake more than it used to. My shifter now also wobbles when coming back to center, where before it would just kick to the right and come right back. I can also feel it shake in the rear when I do this too. What throws me for a loop is that once I drive and everything warms up, this decreases a bit. I'm not sure if torn mounts could cause my issue or not. I had tried to get under and look at them, but I couldn't get a good look around the subframe and the pre-cats

Bill Curlee

Ie say the Diff clutches are GOOD..

Chock the wheels, apply the brakes and power brake the car. Apply some throttle while you TORQUE the drive line. If you have a bad LEFT side engine mount, the engine will try to climb out of the engine bay! (it will rise up off the mount)

They sell some great solid poly mounts now!

I also purchased a used PFADT differential mount that I still need to install.

https://www.corvetteforum.com/forums...torsports.html

GreekBoy229

Thank you Bill. I've tried torquing the motor in the manner you mentioned and I get about an inch of lift on the drivers side, but it doesn't seem drastic (buddy with an '09 has similar movement without any of the issues I have). My shifter bounces on the rebound though, which leads me to believe it is my passenger mount that may be torn. I'm going to order the Hinson Engine and Trans mounts and see if those solve the problem. I'll report back after the install if they fixed my issues. If anything else comes to mind, please let me know. Thanks again