09 CTS Intermittent Shifting/Clutch Issue?

bpoole99

I have scoured this and other boards to see if I can find anyone else having this issue. Unfortunately, the way it manifests itself makes it difficult to describe and hence I am struggling to find someone else having the same problem.

The problem is seen every 20-100 stops in normal stop and go traffic. When the car is brought to a stop, it either does not downshift to an appropriately low gear or something happens with the clutch. Regardless, when foot is removed from the brake, the transmission does not "engage" for several (1-5) seconds. When gas is applied, the car feels like a manual clutch is being slowly removed, until it finally engages and slightly lurches forward - kind of like dumping the clutch. When this happens, I have tried to quickly switch to manual mode and shift, but it does not seem to help. I have also tried to reapply the brake, which doesn't seem to be a magic bullet. We feel that if you stop the car and let it idle forward at the stop, it is less likely to happen, but it is so infrequent that we could be imagining this.

I have taken it to the dealer twice, with no luck, mainly because it is impossible to demonstrate the failure. It is also a bit difficult to describe, leading to the service tech going down what I believe to be dead ends and needless repair costs.

I really think this is an electronic issue, possibly causing the transmission to stay in high gear. However, I could be convinced that is also connected with clutching - I don't know anything about how this transmission works.

Anyone seen this before or have any thoughts on how to get it resolved?

Thanks

Mr_Shiftright

As you pointed out, it is difficult to diagnose a problem that is not present, and then suddenly disappears and resolves itself, only to appear at (seemingly) random times.

So were all the car's systems exhaustively scanned for data, or was the dealer's diagnosis somewhat dismissive?

It may be that you could carefully note the exact conditions under which the problem occurs (speed, temperature, road type, etc) to see if there is indeed a pattern that could tip off the technician.

If not, and if not trouble codes or other data were retrievable, you may just have to wait until it gets worse.

I agree, it does seem electronically related.

BTW, has this transmission ever been serviced?

thecardoc3

When it acts up does the engine race when you step on the throttle? (over 3000rpm) Or does the engine sound like it is working against a heavy load?

Professional level scan tools are capable of taking a snap shot of data over a specific time interval and before we go any further I would want a capture of the transmission control data. The data stream will show me what gear is selected, the gear that the module has commanded and what system the line pressure is. Combine this information with shift adaptives and that would paint pretty clear picture as to what is going on and what testing would need to be performed from there.