2008 Mazda CX-9 Auto Slipping and Shudder

Complete Transmission Repair Cost Guide Transmission Forum – Ask an Expert Mazda 2008 Mazda CX-9 Auto Slipping and Shudder

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    We have a 08 Mazda CX-9 6 speed auto with transmissions issues.
    What’s happening is 1-3 is normal but when in 4, you can hear it slipping by the revs going up, but only slightly. Odd thing is while accelerating the revs go up and then down again and repeats even though I’m still accelerating. Then when it changes into 5th there’s a shudder for a bit and then when it changes to 6th, there is the on and off slipping again. The shudder also happens at intermittent times throughout 5th and 6th which I think is happening when the slipping stops and starts to grip again.

    Thing is I thought if it was slipping wouldn’t it keep slipping as long as I was still accelerating?
    That’s what made me think it must be electronic related so I tried it in manual mode, and it worked perfectly normal in all gears up and down no slip, no shudder. Does this confirm that everything mechanical is ok with the box and that is something electronic like the tcm or sensors or could it be something else? I’m tempted to disconnect the battery overnight to try and reset the tcm and ecu but concerned that I may need to reprogram something if I do.

    Need a replacement transmission? Quality transmissions are hard to find. Free estimate to your email.


    If you shift in manual mode, you are asking the transmission to work more like a manual transmission than an automatic. In other words, when you pick 1st, 2nd, 3rd, etc., you are eliminating the torque converter’s spinup of the impeller blades. In turn, these blades begin to move the transmission fluid through the entire transmission.

    Normally, the transmission fluid whooshes its way through the gears as the changing gear/clutch/band sets engage and disengage in response to valve body inputs as well as solenoid actions. However, when you are in manual gear, you essentially lock up each gear until you hit the next one. In this manner, there is no slippage — except for minor mechanical and built-in fluidic losses that will occur anyway. Instead, there is a hard connection. The proper settings are forced and the transmission works correctly.

    What I think is happening in your transmission — you have pretty much confirmed it with your detailed description — is that your Mazda is down a bit on transmission fluid. What happens is that the level is just high enough to keep things working but not without problems. In this case, the transmission has to work harder to provide enough pressure to make sure that the transmission parts work correctly. And, since there are times when there just may not be enough fluid available, as in a turn when you are accelerating, then the gears/clutches/bands that were engaged correctly, lose their connection because the fluid level drops too far.

    Check the tranny fluid level first. I think you’ll find the transmission is down about a quart.


    I already checked the fluid yesterday. I drained out what I could about 4 quarts, installed a magnafine filter in the return line and topped up with fresh fluid but Ill check it again to make sure.Anything else you think it could be maybe?


    When you drained out the fluid, did you remember to drop the pan cover? If not, you likely have ended up with more fluid in the transmission, probably a quart or so. If you don’t remove the tranny cover to take out the bit of fluid — actually a quart or so — it remains locked up and when you refill it you automatically end up with more fluid. Check the level again as soon as you can and you may find this is the case.

    Are you also saying that the transmission is performing as it did with old fluid/filter? I think your analysis of the transmission’s performance was done before the change out, right? If so, how is it performing with the changed fluid/filter?

    Leaving aside the other mechanical components in the transmission, for now, your next step should be to a transmission shop with OBD-II diagnostic scanner. Have the shop guys perform a check of your car’s engine control system to see if any codes have been thrown and collected by the system memory. At this level, you will find any error codes that may have been generated by a failed electronic or electrical part, or even a mechanical part, if the software covers it, is quite general. However, it will point you in the direction of the issue. You may possibly be able to fine-tune it by checking the transmission control module, looking for transmission-specific error codes.

    Until I have a bit more information in hand, I can only speculate the you are likely looking at a key sensor failure such as the Mass AirFlow (MAF) sensor or the Mass Air Pressure sensor. If either one goes down, your transmission could easily perform in the manner you suggest. The same is true if one of the transmission solenoids (they are located inside and on the valve body) as they determine which gear your vehicle is shifting in to.


    ajhoward, I have a similar problem as you described (same model, same year, same symptoms). Did the actions suggested by mstern001 fix the problem? How did it finally get resolved?



    Same problem with my 2008 CX9. Tired of driving it in manual. I’d love to know if anyone fixed it.


    I do have the same issue, but filling or adjusting the fluid did not resolve the slippage or shuddering. It got worse over a few months now with high grinding noise at high shift (5+). I have been reading many forums on this topic and it made me worry if I need to trade in my CX-9.

    Jack Crowley

    2008 Mazda CX 9 165,000 miles. Since about 140k miles, on mild acceleration or local shopping traffic, between 35 and 50, around 3rd or 4th gear, it seems to slip, as if it wants to up or downshift. Using cruise control on rolling hills ( to simulate inc/dec load, in the same speed range) or using cruise to accelerate, no problems; manual shift no problems. Trans oil and filter flush and change every 40K miles, just had it done 5K miles ago. Fluid never burnt, no excessive material in the pan/oil.

    Sensing it might be electronic. Does this model have a memory that may be confusing the engine-trans interface? If so, how do you reset? Other thoughts?


    Ours is 2008 Mazda CX9 AWD GT with 85k miles. Recently, we have started seeing transmission type problem. It happened between 2 &3 and 5&6 geears at speeds between 40 & 50, 60 & 70 at lower speeds also when at gear 3. It looked like some thing knocks or hesistates or jerks. The drive is not smooth. Some of the posts suggested spark plugs and/or ignition coil issue. Some youtube video suggested a shudder fix lube which was tried but did not help. The transmission shop did not find a problem and they said the transmission changed gears fine and commands looked good and suggested car performance/tuneup issue. So, I got spark plugs replaced at a shop and it is running fine so far.


    You have just pointed out something that is very common, one problem that seems like another. For example, let’s say that when your car accelerates, there comes a point when it seems like the automatic transmission starts to slip. Indeed, it might even refuse to downshift at all when you put your foot into the accelerator to make it happen. It sees clear, at this point, there must be a transmission problem, right? It’s wrong, honestly.

    As you pointed out, the slipping scenario can make you look in one direction under the hood, when you should be looking at the most obvious points of failure, especially if you pull the error codes and there’s nothing to indicate it could be a P0715-style error (0715 is a generic transmission failure code) then you have to look at mechanical failures like the plugs or perhaps the timing chain or even a sensor that is monitored by more than just the transmission.

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