I tested my 89 iroc z 305 on the highway up to 135 mph at full throttle. I had one problem, it shifted at 4500rpm on every gear. I am running a Paxton sn89 with a stock chip. So what does this mean? I am still a newbie to superchargers as of June.

 

The governor in the transmission is what controls the shifts. It has weights and springs inside it, similar to an old-school distributor, that tell the trans when to shift. You need to change the governor to get it to shift higher.

 

He is correct. I changed to a miniram and added a supercharger. I am about to change my transmission governor to raise the shift point.

 

Before the supercharger it would shift at 5800-6000 rpm

 

You might want to check you tach connection. I am talking about the wire that connects to the distributor. Mine was not making good contact and the tach was not reading right. I disconnected it and reconnected it and it now reads right. How does the motor sound? Can you tell it is not revving?

 

I'll check to see if that is the problem, I took off my gauges 2 weeks ago and didn't full throttle it until now. Also, it does not sound like the motor is going above 4500. If you use the drive gear instead of the overdrive on the shifter will that make the car shift sooner. I had the car up to 130-140(speedo only goes to 120) in the drive gear.