pdquick01

iTrader: (3)

I ran a best of 12.59@ 110 2.0 60 on street tires in my 01 z28. And with 410 gears I'm at 6700 rpm in 4th when I go through. I even bumped the rev limiter right when I crossed. I'm scared if I run slicks I'll have to shift to 5th, should I swap to 373,s?

HCI2000SS

iTrader: (2)

There's no way you're at 6700 rpm at 110 mph in 4th with 4.10 gears. Something is off

Guitar

iTrader: (9)

http://www.f-body.org/gears/

With a stock size tire, 275/40/17 right?, you're at 125 at the top of 4th.

pdquick01

iTrader: (3)

I forgot to mention 285/40/18 tires is that my problem?

Guitar

iTrader: (9)

That would give you MORE runout as far as MPH. Use the calculator I posted.

scotty2000ss

iTrader: (2)

Maybe the tach is off?

NW Iowa WS6

iTrader: (9)

Exactly, its impossible for you to be that high of rpm with 4.10's and a 26-27" tire. You would have to have 4.56 rear gears for this to be happening. Most likely your tach is off

Bill00Formula

iTrader: (4)

On a 26" diameter tire (16 inch drag radial) I was able to go 129 mph in 4th w/ 4.10s at 6,800 rpm.

HCI2000SS

iTrader: (2)

I have two questions here: you are trapping 110 so I'm "assuming" you just have bolt ons...no cam? If so you should not be revving to 6700...at all!! Secondly, this may sound like a stupid question but I have to ask anyways...are you sure the speedo is calibrated for the gears? This whole thing makes no sense based on the info that you've given us

Guitar

iTrader: (9)

Another one of his posts said he is making over 400hp so he is probably short shifting the **** out of it with a bad tach.

pdquick01

iTrader: (3)

My car was tuned and made 403 rwhp everything speedo was calibrated to the gears rev limiter set at 6800 witch I bumped at the trap no way I ran a 12.5 short shifting. Been driving this car for three years almost a year with the rebuild I know what 6500 feels and sounds like

pdquick01

iTrader: (3)

Is it possible my clutch was slipping close to the end causing this effect

pdquick01

iTrader: (3)

This is 6th so it's dead on with the calculator I got to figure out what I'm missing, the calculator also says 109 at 6800 in 3rd, have I lost my mind and was in 3rd at the trap

HCI2000SS

iTrader: (2)

You didn't mention about anything feeling weird ir off so I was guessing not

Also I have 4.10's as well and at 6800 rpm I'm showing right around 95 mph in 3rd. Not sure where you're getting 109

Guitar

iTrader: (9)

You were likely at third in the trap then...though unless you shift like a grandma I see no way a cammed car with 4.10s wouldn't be in fourth at the end of the quarter. I get into fourth at around the 1k foot mark (guessing) with 3.90s.

pdquick01

iTrader: (3)

Watched the video def 4th

Guitar

iTrader: (9)

Very simple way to test this. May or may not be illegal. Go make a highway run through fourth and take a video and/or give us results.

pdquick01

iTrader: (3)

I don't know I'm happy with the numbers, I'll drive it tommow and redline 4th see where I'm at. Still running ls7 clutch so who knows, thank you guys for your input.

Guitar

iTrader: (9)

You're happy with a 110 trap in a 400wheel car? No offense dude but that's what a exhaust/gears car could do. My car traps 115 @ 3800 pounds with 3.90s and 386rwhp (before the 9").

I have a feeling you may be either short shifting a lot or again crossed in third. If so..you have a good amount left.

1997trans-am

iTrader: (2)

I have 4.10 gears in my trans-am (T56) and my speedometer is off by about 6 mph. My tach also reads about 200-300 rpm higher at idle than my actual engine speed.

If you really want to check it, you could just run it at half of the rpm (3300-3400 if your redline is 6700) in 4th and double the indicated speed.

It might not be the most accurate way, but it safer and less risky with regards to speeding tickets.

But either way, the stock gauges are not super accurate, at least in my limited experience.