Wierd issue

[MShreve]

I'm hoping somebody else has had this problem and can tell me what's going on.

So a few weeks after I installed my mods (everything but the rear engine mount) I've picked up a very strange clunky noise. If I drive normal it never happens. If I accelerate hard through 3rd and then shift into 4th and let off (decelerate under compression) about 3-4 seconds later I hear this loud clunk come from the rear end.

I originally thought it may be an exhaust hanger from getting torqued around during hard acceleration and then settling afterwards, but I can't find anything loose (I man-handled the exhaust and couldn't get it to move).

The only other thing I can think of is that I have a messed up engine/tranny/diff mount, but I won't be able to use my buddies lift until Wed to get under there and look.

The only other strange part is that after the clunk happens I get some wierd vibes while continuing to decelerate under compression...which eventually goes away after a few minutes of normal driving.

Anybody have an idea of what this could be? I just hope it's nothing serious.

 

[Blendercloud]

Might it be a broken baffle in one of the mufflers?

 

[MShreve]

Might it be a broken baffle in one of the mufflers?

I guess it could be...I've never had that happen before so I'm not sure what it would sound like. But I can feel and hear the clunk when it happens. It feels like drivetrain moving around, but I can't tell for sure. The wierd vibes during deceleration that happens afterwards is the worrysome part. The frequency of the vibes get slower as the speed decreases, which also makes me think this is drivetrain related.

I know exactly what the dealership is going to tell me..."we couldn't find anything wrong. Here's your bill for the labor and rental.". So I'm hoping I can get this figured out without their help

 

[tunersteve]

I guess it could be...I've never had that happen before so I'm not sure what it would sound like. But I can feel and hear the clunk when it happens. It feels like drivetrain moving around, but I can't tell for sure. The wierd vibes during deceleration that happens afterwards is the worrysome part. The frequency of the vibes get slower as the speed decreases, which also makes me think this is drivetrain related.

I know exactly what the dealership is going to tell me..."we couldn't find anything wrong. Here's your bill for the labor and rental.". So I'm hoping I can get this figured out without their help

If its under warranty they won't charge you a dime. They shouldn't at least. Besides, once it goes to the dealer for an issue, it's got a paper trail.

 

[MShreve]

If its under warranty they won't charge you a dime. They shouldn't at least. Besides, once it goes to the dealer for an issue, it's got a paper trail.

They charged me for 2 days of a rental car last time I was in there because the tranny wouldn't shift in or out of 2nd smoothly after they did the clutch TSB. They told me it was working as intended and therefore wasn't covered under warranty. I guess I expect the same treatment for this issue.

Leaving a paper trail is a good idea though.

 

[tunersteve]

They charged me for 2 days of a rental car last time I was in there because the tranny wouldn't shift in or out of 2nd smoothly after they did the clutch TSB. They told me it was working as intended and therefore wasn't covered under warranty. I guess I expect the same treatment for this issue.

Leaving a paper trail is a good idea though.

Wait a sec...I've been to the dealer for issues that couldn't be replicated and not charged a dime. Why is your dealer charging you? Definitely a point of discussion next time you're in. Alternative is taking it to a different dealer if they're not willing to help you.

 

[vrspeedemon]

+1^^^
dealer can never seem to "replicate" any of my issues, but I don't get charged and I feel it's better to have something on record for down the line.

 

[MShreve]

I just dropped off the car at the dealership. The good news is that I was able to reproduce both issues (the clunk and the vibration) with the service manager in the car with me. We'll see what they find.

On a side note, I told them about my erratic LTFT's and they said they couldn't touch it unless it starts throwing a CEL. My LTFT's range from 2.5% to 15.9% now between idle and WOT. It's been 1500 miles since I reset the ECU after installing the CAI.

 

[Rutedown]

When they replaced my turbo under warranty they paid for the rental, but I had to pay for the taxes on the rental. That was the only time I had to take the car in. Does this sound normal or should they be taking care of all of it?

 

[tunersteve]

When they replaced my turbo under warranty they paid for the rental, but I had to pay for the taxes on the rental. That was the only time I had to take the car in. Does this sound normal or should they be taking care of all of it?

Depends on the dealer. I have had them try to stick me with taxes, but got out of that one by going to a smaller car.

 

[MShreve]

The dealership originally thought it was the sway bar bushings, so they replaced those, but the clunk and vibration continued to happen.

Now they're telling me that the cause is that my front tires have 3/32's more tread than my rear tires which is causing binding in the transfer case and/or rear diff (service rep non-technical description).

I understand what he's saying, but I'm having a hard time believing this is the case, as this car was way out of alignment when we bought it, which caused the front tires to wear very fast and we never had this issue. This is a brand new set of tires that I just rotated. So if he's right, I'm never going to be able to rotate tires without causing issues?!?

Do you think it's just a matter of putting the smaller diameter tires on the front instead of the rear? I'm hoping that will keep the DSC from trying to lock up the rear axle because it will always think that the back tires are spinning faster than the fronts.

What else can I do?

Any input is appreciated.

 

[MShreve]

BTW, I just got back from the dealership and they charged me for labor because this issue isn't covered by warranty.
Thank god I didn't let them talk me into a rental car this time around.

Time to find yet another dealership. This will be the 3rd one. (bang)

 

[tunersteve]

Is your car out of warranty? Labor is covered.

If I were you I'd be getting on the phone with MNAO and finding out why you're getting charged, and start looking for a dealer that can put an end to this issue for you. Any others in the area that are reputable?

 

[MShreve]

Is your car out of warranty? Labor is covered.

If I were you I'd be getting on the phone with MNAO and finding out why you're getting charged, and start looking for a dealer that can put an end to this issue for you. Any others in the area that are reputable?

I just got off the phone with MNAO. They agree that the dealership should charge for the diagnostics labor in this case. They refered to it as a problem caused by "outside influence", meaning the tires.

I'm going to rotate the fronts and rears today and see what happens.

I can't believe that nobody else has been through this. I wouldn't think that 3/32nd's of an inch difference would be all that uncommon between tire rotations for anybody that drives hard.

 

[MShreve]

BTW, the tires were the issue. After I also replaced the rears the clunk and vibration went away.
Apparently 3/32 of an inch difference in diameter between front and rear is all it takes to cause the diff to freak out. This issue also voids your drivetrain warranty if you ignore it. So make sure your alignment is correct, rotate often and never replace less than all 4 tires.