I've had my RX8 for a couple of weeks. Right now its back at the dealer.
I wanted to find out if anyone else has had this problem with the 6-speed auto.

Out on the highway (speed limit is 55 - 60 mph) with some slight hills, it will shift up into 6th gear around 55 mph. Crusing at 60 mph, the tach will sometimes drop below 2000 RPM (less pressure on the gas pedal to stay around 60 mph), as soon as it drops to 1800 RPM, the shifter **** will visible shake back and forth about 1/2" up and down from where it should be. I can floor it, forcing it to downshift, or switch to M mode, and it'll be fine.

To give you an idea, I was on the interstate yesterday in a construction zone, was doing 50 / 55 mph, it shifted into 6th gear, dropped below 2000 RPM, started to shake. It was impossible to leave it in auto, and maintain the 55 mph speed limit. Prior to that I was in a 65 / 70 mph zone for about 80 miles, and it never had the problem once.

Dealer thinks this is normal, thought I'd get a second opinion.

 

The "shake" you described is the engine lugging. Best way to avoid it is to use the manual mode; unfortunatly there is no other way to lock out the overdrive gears (5th & 6th).

 

That sound right. The AT computer isn't quick enough to pick the best gear for drivability, just for fuel econ.

As a comparision. the 6 speed on the Cx-7 when you lightly press on the gas will shift up as to pass.

Best fix for this: try the Manual mode and become one with it.

 

Thanks. I figured it was normal but its nice to know there is nothing wrong with it!

Interestingly enough it never happens on the same road, same speed with crusie control on!

 

Interestingly, the 4AT does not have this issue It does shift to 4th to save gas, but the rpm is decently high (and unless the engine mounts are bad, it won't shake). Actually, I suggest the dealer checks those mounts, as they are known to get bad (and when that happens, tranny is misaligned and shifting can be impaired in extreme cases)

 

I also have a 07 with the 6sp at, I have takin it to the dealer twice for this same reason as it can be somewhat violent. If this is the case at it is normal than Mazda needs to do some reprograming with the TCM to lock it out of 6th below 55.

 

i had the same problem with my 06 AT sspd, then i found it its not bad or anything so i dont care.

dont sweat it, its no problem..

 

I've had this problem before!! I was being (very) retarded one morning and decided to floor it while it was still cold. HARD FAIL! I get some violent shaking and a nice new CEL to look at. After driving it a while, I notice that if I try to slightly accelerate while in 5th or 6th, it would NOT shift, it would only shake. Shake bad enough to feel it in the steering wheel. Not to mention I could barely accelerate in any gear. I took it in to the dealership and drove around with the Mazda service tech to reproduce the problem. We conclude that it is the spark plugs fouled. He replaces the plugs under warranty and reprograms the PCM so the car would start nicer, in his words.

I drive it home and the acceleration is much smoother and powerful, and the shaking completely disappeared.

 

I'm sorry but this is totally wrong. A slushbox that doesn't know how to downshift to prevent lugging is basically broken and need to have it's PCM program revised. WTF is wrong with Mazda?

 

Funny my 05 AT is similiar. It wants to get my to 4th as soon as it can. There has been times when I will be going 20mph in 4th and it feels as it is going to stall... I tap the gas pedal briefly and that will make it shift to 3rd or 2nd.

 

Lugging the engine is bad. The computer is retarded. Just use the manual mode. I figured this would be a problem when I first saw the gear ratios on the 6 speeds. 6th gear + the final drive is too low. They're fine for highway cruising, but if you intend to accelerate or drop below 2k rpm, do your engine a favor and downshift. There's no effort in using the manual mode, just a thumb press or finger tap every now and then. And if it saves you from 2 weeks in the shop getting a new engine, it's worth it.

 

dude, I got 07 same thing man, everytime I go up on highway, for that matter, most of my driver.......is in semi manual.....god I miss the clutch!!!