C.T. from AutoZone (yes, that AutoZone) writes:
Dear Piston Slap, I drive a 2002 Audi A4 1.8T with the CVT. It has 75,000 miles on it, and has been properly maintained. I am experiencing a vibration under these conditions:’
-Only after at least 10 minutes of driving…never cold
-Only between 70-80 mph
-Only when accelerating
-The same no matter how much throttle I give it
-I cannot feel it in the steering wheel
-It feels like it is coming from the axle/drive shaft area
-Sometimes it doesn’t happen at all
I recently took it to a reputable independent shop I have used several times to perform the timing belt and drive belt swap recommended before 80,000 miles. I mentioned the vibration, but they could not replicate it (although I am sure they drove it cold). The vibration was happening maybe 1-2 days a week then. Now it is happening 9 in 10 days under the conditions above. This is probably the only place I trust with my car where I live, but they are so busy right now that I’m afraid they still won’t take the proper time to do a 20-minute highway test drive to properly diagnose the problem.
I don’t have the time, the tools, or the skill to DIY this. I have searched the Audi forums for answers and most blame their mods for their vibrations. I’d like to be able to give my shop a better idea of what it might be…they are more likely to spend the time looking at the car on a lift than test driving, so if I can get them going in the right direction, maybe they will find and fix it.
Help me Piston Slap, you’re my only hope.
Sajeev answers:
And with that: help me, Best and Brightest! This week’s Piston Slap comes from India and Internet access is, uh, somewhat limited. And intimate knowledge of CVT repair/diagnosis is quite hard to find outside of a stealership service bay. But that’s not to say that CVTs aren’t worth their weight in gold to someone.
I reckon you have a mechanical problem internal to the CVT, since you mentioned that the problem happens as the car’s fluids warms up. Failing sensors or worn CV joints need not apply, but a used CVT from car-part.com runs $800-1000 and the labor is several hundred more. That’s probably your only route, as locally rebuilding a CVT is almost entirely out of the question given the complicated nature of CVTs.
If your mechanic is still clueless after the road test, I suggest a change of plan: add a bottle Lucas (purchased with your AutoZone rewards card, wink-wink) and sell it to a faceless dealership, or Carmax. Bad Karma to the next owner be damned, I suspect far, far more terrible financial pain in your future should you not heed this advice.
And if you’re a modern hot-rodder who loves getting on the boost, I’d recommend choosing a more robust platform for your future modifications. You know, if you did that in the first place.
[Send your queries to mehta@ttac.com]
If it were a regular transmission, I’d almost suggest torque convertor shudder, but I’m not all too familiar with CVTs. Sounds like it may be expensive, whatever it is. I’d probably pay some diagnosis time to a shop to find out if I wanted to move forward or not. Someone more intimately familiar with the Audi and its CVT would likely have an idea what it is pretty quickly.
Have you tried the different preset ratios on the CVT to try different engine RPMs at the same 70-80mph vehicle speed at which the vibration occurs.
BTW… the CVT is a horrid, evil transmission (just my opinion). The ZF slushbox is a slightly less evil contraption than the CVT. Don’t get me wrong I also despise automatics (I’m in the process of installing the manual gearbox in my A4 Avant because I thought so highly of the automatic). Somewhere between control unit failures… just outright failure and the cost of either of those I decided the CVT is among the most diabolical gearboxes Audi has ever used.
… or you could not drive between 70 and 80? Ditch the thing, sounds like an expensive repair on the way when it fails.
I watched a program on TV about those monkeys in India that open windows, live on your roofs, bacically get into everything. Maybe its one of those monkeys that got into your car.
…add a bottle of Lucas and sell it on to the next sucker…hey, somebody did that to me
I sure didn’t appreciate it
If it were a regular transmission, I’d almost suggest torque convertor shudder, but I’m not all too familiar with CVTs.
Some CVTs do come with a torque converter, but since it varies with speed and not with throttle, I’d wonder if the output pulley or something connected to it is loose and hits it’s harmonic sweet spot at 80 once things have slackened due to warming up.
Are you able to get diagnostic information about the ratio the CVT is at when the vibration hits? Or does it happen at a given combination of RPM and wheel speed?
…given the complicated nature of CVTs.
They’re not actually that complicated. Crack one open and it’s actually blessedly simple next to a conventional five-speed auto.
What they are is unfamiliar. Which, in the end, can equate to the same thing. I quite like them, but I’ll admit they’re a bit of a gamble.
Ah ha!
The infamous Audi/VW coil pack syndrome (CPS) strikes again.
Check your coil packs as you’re probably about to become stranded roadside if I’m correct….
Whoa, hold on now. Why is everyone automatically blaming the transmission?
Can I assume that you haven’t checked the easy stuff first?
This type of speed-related vibration could easily be a damaged or out-of-balance tire. I’ve also heard of cases where bushing wore out on the suspension (can’t remember if it’s front or rear), and that was the root cause of this type of vibration in a few cases.
@ohsnapback
Failed 06B-905-115-R coil packs cause engine vibration all the time. The intensity of vibration on that would also be engine speed dependent not vehicle speed dependent.
This type of speed-related vibration could easily be a damaged or out-of-balance tire. I’ve also heard of cases where bushing wore out on the suspension (can’t remember if it’s front or rear), and that was the root cause of this type of vibration in a few cases.
If he’s saying it’s not something he can feel through the wheel but is coming from the front of the car, it’s probably not suspension, tires or brakes. At least that’s been my experience (worn rotors, bent control arms, shifted belts.
The bushings might be a good place to start, though. If you can get it to happen, does it go away or change if you turn the steering wheel at speed? Any other noises (clunking)?
The infamous Audi/VW coil pack syndrome (CPS) strikes again.
Don’t they normally throw a CEL and or manifest far nastier symptoms than just vibration?
I would definitely look at the more obvious things first, i.e. the exhaust system, mounts, cat, etc., engine/transmission mounts. Look underneath the car, preferably when it is on a lift and grab hold of anything that looks like it could cause a palpable vibration and see if things are loose or contacting some part of the car that they shouldn’t be contacting. Also, check for a wheel bearing that is overheating.
I have encountered drive-train problems that make noise and let you know that they are getting ready to grenade themselves without ever having had them produce a vibration; it may well be something much simpler.
highrpm +1
When I feel speed specific vibration in a car the culprit is almost always wheel weights or alignment. I wouldn’t even consider the transmission a source for this if you didn’t have the awful CVT.
For what its worth, Audi has not come up with a work around for the typical CVT issues, and yet they spec. the tranny as the only option on new FWD no-clutch A4’s. It’s bizzare, and makes me think that someone at VAG really misses VW’s well deserved 90’s-era quality reputation. They must be hoping that no one who knows cars or drives hard will buy one.
I would check out the half-shaft CV joints before blaming the transmission.
Here’s a question: can you get it to happen when the car is either on a lift or dyno?
qfrog, thanks for reminding me this is “vehicle speed” and not “engine speed” dependent.
psarhjinian, the three people I know who has problems with the coil pack failures received no warning from their dash before their cars died, roadside style. For the record, all had Audi A4s. They were really popular circa 2001-2004ish-ish.
+1 on checking the engine + trans mounts before changing anything. You should be able to do a quick visual without removing anything, although keep in mind that the bushings could look ok on the car and still be badly worn. With that many miles and driving on Indian roads (likely almost as bad as the ones here in Mass), I’d say now is a good time to change the bushings anyway.
I go with the CV joint diagnosis. Vibration would be speed sensitive. If the tires are worn try rotating the tires to see if the vibration moves. Could have lost a balance weight.
Audi Update!
Since submitting this request, the vibration got much worse and happens all the time, regardless of speed or engine temp. Makes it easier to diagnose, no? Took it back to my indy shop. Diagnosed as bad motor mounts. Front was gone, right was leaking bad. Fixed now, and drives like a dream.
That Craptatic VT is somebody else’s future problem now, though. Sold it the day it came back from the shop. Wife missed her front wheel drive and hated that Audi like it stole her boyfriend. She gave me her 08 G35 Sedan, and we got her one of the last 3 red 09 TSX’s with nav left in the country for less than invoice.
I hate parting with my fine German automobile, especially since it was finally running right, but if you have ever driven an 2002 Audi A4 1.8T back to back with an 2008 G35, you’d know it wasn’t so bad.
Thank you, Best and Brightest!
Thanks for the update, Cole.
psarhjinian : What they are is unfamiliar. Which, in the end, can equate to the same thing. I quite like them, but I’ll admit they’re a bit of a gamble.
I stand corrected.
Those of you saying that this is the result of a blown coilpack, clearly have never blown a coilpack in a 1.8T.
I blew one a few months ago in my ’05 1.8T (after chipping it), and the resulting vibration does not happen every once in a while. It’s a constant, horrendous shuddering that runs through the entire car (an engine normally balanced for 4 cylinders is only running on 3!). The car will be damn near undriveable.
To me, it definitely sounds like a CVT issue.
I don’t know why tires and suspension wouldn’t be the first things to check. These can be inspected for wear, imbalance, etc. without replicating the problem itself. I would suspect some combination of these as the culprit.
Edit: I missed the above post about the problem being solved. Sorry about that.
I don’t know why tires and suspension wouldn’t be the first things to check. These can be inspected for wear, imbalance, etc. without replicating the problem itself. I would suspect some combination of these as the culprit.
I think it was because he noted he didn’t feel it through the steering wheel. Usually you’ll feel (and see) the imbalance that causes as vibration in the wheel.
I kick myself for not thinking about the motor mounts. My Saab busted two over a period of six months and exhibited about the same symptoms. I think the lesson here is that we all distrusted the CVT and were too willing to find it at fault, or we didn’t listen to his description of the issue.