Rohan

Ok, I have been stationed in Louisiana and I decided to bring my Corvette over here with me. I have been driving on these HORRIBLE roads for about 3 months. Now all the sudden I have noticed that when I go over really bumpy parts of the road, the overdrive will suddenly go out and my RPMs shoot up by a few hundred then it will kick back in and the RPMs drop again. Sometimes it will do this on and off really quickly and sometimes the OD will just go out and stay out until I slow waaayyy down or stop and then it will work again when I get back up to speed like it's supposed to. I usually run about 2000 RPM at 75 - 80 mph but when the OD isn't working properly I run about 2000 RPM at only 60 mph. It's getting frustrating. I never had a problem before I moved over here where the roads are ridiculous. Oh another thing... When this happens I noticed that the Cruise Control won't engage but when the OD is working then the Cruise Control works fine. ANY IDEAS?

1badf350

DUDE!!! I had this exact same problem the whole first 6 months I owned my car. I can tell you with 100% confidence that the problem is the brake pedal switches needing adjustment.
Think about it. When the brake switches sense that you have applied the brake, what do they do do? Besides illuminating the brake lights they unlock the torque converter, which is why you see the slight revs in RPM. They also disengage the cruise control.
What happens when they are out of adjustment is the switches "chatter" against the brake pedal when you hit bumps and the car thinks you have hit the brakes.

You can easily do this yourself up under the dash. The switches, there are two from what I remember, are up above the brake pedal.

I forget exactly how to adjust them but it was ridiculously simple.

Just do a search here on "brake switch" or "brake pedal switch".

I would not wait to fix it though because I firmly believe it contributed to my trans failure.

C5XTASY

As mentioned above, it sounds as though the torque converter is unlocking and then relocking as touching the brakes will cause an unlock. Also, it probably is the brake switches as mentioned, however, misfires can also cause the torque converter to unlock. Just a FYI.
Ed

Rohan

WHOAA!!! I would have never guessed that! It makes sense though. Since my car doesn't misfire I'm gonna go with the brake switches as being the culprit. Thanks so much for the help!

C5XTASY

As I said it, probably is a brake switch. The possible misfire gives you another path in case the brake switch doesn't fix the issue. Don't forget, you can't necessarily feel a misfire.
Ed

Rohan

Well I went for a 100 mile drive on the highway this weekend and tested the brake pedal theory. Once the problem started I pulled back on the brake pedal with my foot and "poof" no more problem. The car went back into OD and I was able to set my cruise again. I really didn't think it was going to be a misfire because I put in new coils, wires, plugs, and injectors in last month. Sooo, looks like I'm gonna have to adjust my switches out to contact the brake pedal. I guess after a while your pedal gets some play in it and therefore causes these kinds of problems. Good thing GM installed adjustable switches. Thanks for the tips guys!