Well if you have a 255 tire (I saw that you used 245 in your calculation but stated previously that you had a 255). You can use the next equation down in the calculator section, and in 5th gear (.63) with a 3.42 rear and a 255/50/16 tire I get 3971 rpm or right around 4k for 140 mph.

115 for me.... damn speed limiter

112 so far since the engine swap. Did 124 mph a few years ago when I had 3.08 gears and the 305

The stock steel driveshafts in out cars are prone to fail at speeds over 150mph, I don't think you want that happening.

That's with 3.23s gears or so. If you're running 3.42s... 3.73s you will approach that critical speed faster.

i used 245 becasue that what the car came with..and at 143 mph the tach is right around 4,500...
as far as the driveshaft is concerned,...with 3.42's the speed at which "critical DS speed" is reached is at 134mph....and about 120 she starts making weird harmonics lol....

What type of driveshaft do the vettes with the tranny in the rear use?

Anyyone know at what speed the Aluminum drive shaft reaches critical rpm?

That depends on the diameter of the tube, the length of the tube, and the exact alloy used.

Great topic, and fun reading! I've only had mine up to 125--with the tops off, lol.

It was on a long, flat section of freeway somewhere in AZ. I could see ahead for miles, and there were no cars anywhere, so I went for it. But once I caught up to some traffic and passed it like it was parked, I decided I better slow down, lol.

The rush(what a rush!) comes after you slow down! I'm sure my blood pressure would've broken the doctor's gauge, lol.

the 1LE DS has a critical speed of 154 IIRC

What about the LS1 shaft and the Spohn Super duty shaft? Anyone have any ideas on those?

I'm guessing the spohn is a lot higher since it's suppose to be a lot beefer. Course with add'd strength of Steel means it's gonna weigh more than an LS1 aluminum. Course I'm just guessing anyone got a spohn DS?

A chromoly driveshaft probably doesn't weight that much more than an aluminum one. The critical speed for chromoly is significantly less than aluminum though. Carbon fiber still has the highest critical speed.

Considering the packaging limitations of the torque arm and the portly demeanor of a street going 3rd gen I'd opt for either chromoly or mild steel. Mils steel has a critical speed that is about 1,500 RPM higher than chromoly, but it is significantly heavier.

I have a stock 305 tpi with 2.77 rear gears and a 700r4 with a shift kit and corvette shift servo I hit 140mph the cars lowered on eibach sport line springs and subframe ties it felt very stable before all those upgrades the car would shake like a airplane going down the runway at 120mph