My car is a 2001 z28 with 94k miles and only mods are K/N airfilter and flowmasters. At 110-119 mph in 5th gear at 4k Rpms the tranny knocks and the car bogs down. Before this happend it was not leaking oil and now its is leaking 1 drop every 4-5 hours.

 

AFAIK, There's a factory speed limiter around 120 if your car didn't come optioned with speed rated tires.

Why are you going 119 mph in 5th gear anyway?

 

i bought it about a month ago and dont know the gears but if i were in 4th id be redlining it at 119. forgot to mention it is a six speed

 

It probaly does have the factory speed limiter, i dont know just thought the tranny shouldnt be knocking at 110ish anyway. Thx for the answer though

 

You must have some 4.10s in it.

 

Yea 4th got me to 140 before I put 4:10s in it. I would research your car more since your not sure of your gears who know what else you dont know about the car, ie other mods and/or problems that the previous owner had. Either way, what your describing is not a problem you should be having in a car that is in good shape. And I might be wrong but if he did not get the speed rated tires his speedo will only go up to 120 but I didnt even know that was possible on LS1s. I thought only LT1s had to get a tire option.