[jblackburn]

Seems like a couple people have had their CTD transmissions replaced for exactly the same behavior.

 

[jblackburn]

It definitely seemed to be very happy, for months, when I filled it following the "proper" procedure.

So, either it leaked fluid out again, or something is physically just taking a ****. Based on the fact the couple failures seem to be similar to what we're experiencing, I'm thinking this likely has nothing to do with fluid - especially since it's so intermittent. When our fluid was low, you could basically count on it to be useless.

The stop-neutral feature on the Aisin 55-50SN was problematic for 99% of them. Often a huge jolt or slow engagement as they got up there in mileage.

Most that owned that transmission disabled it or had to replace solenoids.

Surprisingly, it doesn't seem to be an issue for the 6T GM transmissions, but there may be something about the Aisin boxes that still don't like it.

 

[jblackburn]

Since almost new mine has sometimes downshifted hard. I believe these are dual clutch transmissions. That means it attempts to predict the next gear since it is basically an automatically shifting manual. If it thinks you are going to accelerate but you actually brake, the way it downshifts will be jarring.

For example, if you are in 2nd and accelerating it will prep 3rd. But if you suddenly brake it has to go back to 1st where it was ready to go into 3rd. This behavior makes predictable shifts very smooth and improves fuel economy, but does have some downsides.

Traditional torque converter automatic.

Just crap programming.

 

[jblackburn]

Oh hmm, according to the Wiki article "The shifting of gears is managed by a sophisticated computer programme which oversees a clutch-to-clutch actuation. Gear changes are accomplished by one clutch engaging the instant the clutch from the previous gear disengages." Of course Wiki isn't always right but to me that sounded like dual-clutch.

Anyways, thanks for clarifying that.

Not sure how many clutches are in the Aisin in the diesel specifically, but most automatics these days like the 6T/9T GM transmissions have a bunch of clutch plates internally to control changes between certain gears, and a series of solenoids that activate those clutches. They also use the torque converter in between shifts as another sort of clutch to ease shift shock between gear changes. These are traditionally slower to change gear than DSGs, but are much smoother in low speed and stop-and-go driving.

The clutch plates are on the left side of the image for the 6T40 - quite a few more than just the two found in a dual-clutch.

A dual clutch is more like a manual transmission setup controlled by a computer - more commonly used in performance-oriented cars (VW GTI, Porsche PDK, exotics) for their quick gear changes, but most American drivers don't like them because they're jerky and clumsy at low speed. The cars I've driven with one - Hyundai Elantra Sport, Mercedes CLA, and even the VW GTI (Mk7) - are terrible in traffic or creeping forward on hills. Odd gears are shifted by one clutch; even by the second, so it's much quicker to change gears.