Has anyone felt a rapid deceleration when letting off the gas on the highway while u were going over 50 mph? I have a 99 Z28 w/ a A4 transmission . It feels like a manual transmission downshifting when I let off the gas at highway speeds. Thanks

 

You're probably feeling when the fuel cuts off. After you let off for more than a second or two, the pcm cuts the fuel entirely to improve mileage. Until you get down closer to idle rpms anyway. If you just barely touch the gas, you can feel it come back on...

 

Unlike many cars, the torque converter does not unlock when you take your foot off the gas at highway speeds. Thus it is like a manual tranny car in that engine braking is occuring.

 

Yep, and it's a quite noticeable sensation compared to other automatic cars ... I wonder what the reason for that tuning choice was. I might be wrong, but I don't seem to recall my 94 Formula A4 doing that.

 

I was thinking about clutch wear, but I've ridden in cadillacs with a Northstar V8 that unlock when coasting.

If you have programming software, you can easily change that.

 

Converter lockup and unlock are MPH-for-TPS tables
and it's quite possible that you are just locking the
TC at higher MPH, lower TPS (like closed, and the
table does not unlock at 0). But it could, if you
wanted.