Just had a scary incident with what may be a problem with the ZF 9-speed transmission in my SH-AWD TLX. I am very interested to hear if anyone else has experienced anything similar. I'm including all the details I can, though some may end up not being relevant, in case someone has an idea as to what happened.
Midday, mild temperature (~50 degrees F), clear weather. IDS set to normal. Started car and drove secondary roads to Interstate. After approximately 10 minutes I exited the Interstate to an off-ramp so that I could turn left onto a secondary road. Light at end of off ramp was red and there were several cars stopped and waiting. I came to a normal stop behind the last car and the TLX performed an idle stop as expected. Light turned green and all cars except one directly in front of me proceeded. I waited a few moments then honked the horn to get them to go, after which they took off. I pressed on the accelerator to follow and as expected the engine started and I began to roll. I probably got up to about 10mph before they began to stop somewhat suddenly again because the light turned yellow. :whyme: I put on the brakes to also stop and simultaneously I got the BRAKE and flashing heads up warning. I was applying brakes moderately hard but definitely not enough to trigger antilock brakes or anything like that.
Here's where the problem occurred. While braking and while warning light flashing, a loud, grinding, metallic gear-on-gear sound emanated from the front of the vehicle. I believe I also felt vibrations through the floorboard. Again, I am familiar with the feel of anti-lock brakes and this was very different. The "click-click-click" sound, machine-gun rapid at first, slowed as the vehicle speed slowed and finally ended with a definitive "clunk" just before the car stopped. There were no additional dashboard lights or indicators, and the engine continued to run normally afterwards. The stoplight went green again and both I and the car in front proceeded normally through the intersection.
I immediately turned into an empty parking lot and tried in vain to reproduce the problem by starting and stopping in the same way. I could not get it to happen again.
The ordeal was very disconcerting and didn't sound like it had done any favors to whatever engine parts were involved. My best guess (and it is only a guess) is that it had something to do with the way in which the ZF 9-speed transmission "dog clutch" operates (see here). It certainly sounded like a bad synchronization or someone "grinding the gears" in a stick shift. What doesn't make sense, though, is that I had not accelerated nearly long or hard enough to get anywhere near the first dog clutch shift point, which the above link says happens from 4th to 5th gear.
Has anyone experienced anything like this? Not what I expected from a 1 month old car with 1000 miles on the odometer! :annoyed:
Midday, mild temperature (~50 degrees F), clear weather. IDS set to normal. Started car and drove secondary roads to Interstate. After approximately 10 minutes I exited the Interstate to an off-ramp so that I could turn left onto a secondary road. Light at end of off ramp was red and there were several cars stopped and waiting. I came to a normal stop behind the last car and the TLX performed an idle stop as expected. Light turned green and all cars except one directly in front of me proceeded. I waited a few moments then honked the horn to get them to go, after which they took off. I pressed on the accelerator to follow and as expected the engine started and I began to roll. I probably got up to about 10mph before they began to stop somewhat suddenly again because the light turned yellow. :whyme: I put on the brakes to also stop and simultaneously I got the BRAKE and flashing heads up warning. I was applying brakes moderately hard but definitely not enough to trigger antilock brakes or anything like that.
Here's where the problem occurred. While braking and while warning light flashing, a loud, grinding, metallic gear-on-gear sound emanated from the front of the vehicle. I believe I also felt vibrations through the floorboard. Again, I am familiar with the feel of anti-lock brakes and this was very different. The "click-click-click" sound, machine-gun rapid at first, slowed as the vehicle speed slowed and finally ended with a definitive "clunk" just before the car stopped. There were no additional dashboard lights or indicators, and the engine continued to run normally afterwards. The stoplight went green again and both I and the car in front proceeded normally through the intersection.
I immediately turned into an empty parking lot and tried in vain to reproduce the problem by starting and stopping in the same way. I could not get it to happen again.
The ordeal was very disconcerting and didn't sound like it had done any favors to whatever engine parts were involved. My best guess (and it is only a guess) is that it had something to do with the way in which the ZF 9-speed transmission "dog clutch" operates (see here). It certainly sounded like a bad synchronization or someone "grinding the gears" in a stick shift. What doesn't make sense, though, is that I had not accelerated nearly long or hard enough to get anywhere near the first dog clutch shift point, which the above link says happens from 4th to 5th gear.
Has anyone experienced anything like this? Not what I expected from a 1 month old car with 1000 miles on the odometer! :annoyed: