By on June 3, 2013

Keith writes:

Mr. Mehta,

My apologies if this has been covered, but I’m looking for advice on my soon-to-be out of warranty 2008 GMC Acadia. I’m at 64K and 4.8 years, so bumper to bumper is gone but power train is still good for a few months.

Two fellow Acadia owners I know have reported tranny problems at roughly 60k and the forums seem to indicate numerous others with similar issues. Most often its an issue with the wave plate, particularly with the 07-09 models. Within the last few weeks I’m also starting to get an intermittent stabilitrak warning light promoting me to get the brakes serviced.

My question for you is should I 1) hope the tranny drops in the next two months 2) shell out $3k for a 4/48 extended service contract or 3) trade it in on something similar.

I love the car(truck) and was hoping to get 8-10 years out of it, so maybe #2. Or I could take the $3k and couple that with what I think is still pretty good resale value and get a new ride.

I’m generally pretty cynical about extended service contracts/warranties, but I have no experience on those for automotive.

Any thoughts, advice or general musings would be greatly appreciated. TTAC is wonderful resource. Keep up the good work!

Sajeev answers:

Now’s a good time to remind my dear readers that I am not a mechanic by trade, I’ve just been in “your shoes” in the past. Perhaps an oversimplification, but let’s do this thang and dig into your tranny.

This is the first I’ve heard of this problem, ditto the “wave plate.”  I suspect most of you are in my shoes, so a little research: this thread points to the wave plate vs. conventional clutch plate of the 3rd gear drum (i.e. direct drive, 1:1 ratio) of an older GM 4-speed.  Which I then recalled while hunting for a good rebuilt-upgrade for my Ford AOD. I learned about an upgrade to 3rd gear, choosing an aftermarket Blue Plate Special (yes, really) clutch pack for mine. With that in mind, reading one of the comments in the LS1 Tech link said it all:

“The waved steel keeps the splines from taking a hard hit by pre-loading it. In other words, the waved steel takes up the slack before the clutches are completely applied.”

So if the waved steel clutches aren’t the right “wave dimensions”, there could be a problem shifting into that gear. The problem might look like this. Note how the speedometer never slows down as the rpms fluctuate: indicating that the transmission is slipping that frickin’ hard on the upshift:

FINALLY: a transmission almost as horrible as the one in the Smart Car, without the need for Smart Car ownership! (childish giggling)

Unfortunately we don’t know if this video is indicative of your problem. Or if this thread on the Saturn forums also applies. Or if you have a problem yet…is nothing ever easy in this world???

My advice?  If/when the wave plates start ruining your ride, see if your homework (including the stuff I posted) can get you a little credit with GM service: pleasant, level-headed customers can easily get their out-of-warranty work covered under the blanket term of “goodwill.” Because nobody wants to lose a good customer, if possible.  If not, get a reman transmission that specifically addresses this problem. I suspect both GM and big name rebuilders (like Jasper) will have you covered. Even if it’s gonna happen after the warranty expires.

Perhaps you should just give up and get a Crown Vic Best of luck, as always.


Send your queries to [email protected] Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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11 Comments on “Piston Slap: A New (Wave Plate) Sensation?...”

  • avatar

    It is as if transmissions keep coming up with new ways to fail.

  • avatar

    If I understand the OP’s letter, he doesn’t acutally have a transmission problem at the moment, but he’s concerned that he might in the future because some other owners have reported common failures.

    If that’s the case, and the current only issue with the vehicle is the intermittent stabiltiy control warning, I’d recommend to just keep running it with regular maintenance. Service contracts rarely give you any return value except the the “peace of mind” of the insurance you bought.

    There’s a strong chance the transmission never experiences this problem, and even if it does, there’s a strong likelihood that a reputable independent transmission repair shop will be able to fix it for less than the cost of a service contract, especially if it’s a common issue.

    So I say keep it well serviced and drive the wheels off it.

  • avatar

    Considering the many and various ways our automatic transmissions have failed, even the long used variations of four-speed overdrive units, I have to wonder what the prospects are for these new DSG types being sold by various makers in many different vehicles? The philosophy of these designs goes back decades, yet I’m skeptical of their long-term reliability. I remember an “electric hand” device my Father kept as a desk souvenir that was from a 1930’s Terraplane, which was a pre-selector three-speed, so the engineers have pondered this for many years. My question is are these new transmissions a time bomb waiting to go off in millions of cars world-wide?

    • 0 avatar

      The timebomb factor is really dependent on the quality of aftermarket support. And the training/parts available to the aftermarket.

    • 0 avatar

      Only the complexity of the output shaft (look up DCT’s on how stuff works) and the interface between blocker rings, clutch, etc would be my only worry. Also something to think about is the electronic controls complexity is increased.

      Besides that, the wear points are isolated to the clutches so the number of critical wear components are reduced (I think). Sajeev is right – get enough of these on the road and you’re good to go as far as aftermarket support goes.

      Now, if you’re talking about current model quality, that is another story. DCT’s get a bad rap as they’re noisy pieces of kit.

    • 0 avatar

      DCT have 2 clutch plates as opposed to one in a standard manual. You would think that the transmission would last twice as long but… This discussion isn’t going to help Arcadia Keith.

  • avatar

    Second thought: Just save up a few more dollars and get a newer one with a 6-speed auto? If you are going to spend $3k on an extended warranty, why not apply that price to a newer model year?

  • avatar
    Domestic Hearse

    Is it paid off? No more payments? Keep it. It’s free transportation here on out, except for maintenance, repair, and insurance. Even if you need a $1000 transmission repair a year or two in the future, you’re still ahead.

    If you’re still making payments and have some more to go, dump it. Get your equity, plunk down some cash along with it and get something which will not require both monthly payments AND repair outlays. Payments on a vehicle out of warranty is always double jeopardy.

  • avatar

    Be thankful you aren’t driving a VW which would have some random, expensive part fail at 100 thousand miles. Oh! wait…
    Seriously though, start making extra payments and kill any debt there is. Once the car is debt free keep some reserve cash for in case the tyranny goes. A debt free car in good shape is a far nicer thing to offload than a broken one with payments still due.

  • avatar
    Eric the Red

    I had the sibling to this vehicle, ’08 Buick Enclave. Ordered it from the factory and loved it for 4.5 years. My wife and I both got a lot of compliments and it really was a great riding vehicle. Then the #$%* hit the fan. A/C, water pump, squeaks, rattles, trim pieces. But what really put me over the edge was the dealership that couldn’t ever seem to fix anything and generally broke more than they fixed. Usually my wife would call me within minutes of picking it up from the dealership telling me what was not fixed or what was now not working right.

    I had less than 80,000 miles and had planned on keeping for some time but just lost all faith in the vehicle. If I was going to make repair payments then might as well make car payments.

    I traded it in on a 2012 Ford Flex and once I got used to the styling, have grown to love it. It holds almost as much as the Enclave (all Lamdas are pretty much the same size) but it handles a bit better and get a slightly better gas mileage. I feel confident it will hold up better. I also can tell my vehicle in a parking lot as not as many Flexes as Enclaves.

  • avatar

    Turns out the stabilitrak issues were the result of a bad master cylinder seal causing a leak into the brake booster….another not-uncommon problem on these vehicles! After 4 trips, in 3 days, to the dealer (another story) it’s all good and no tranny issues so far. Warranty is done, but a new tranny still cheaper than extended service. Thanks all!

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