Auto trans in 3rd gear. Does anyone know what the mph would be?

 

Anybody?

 

About 119 mph, assuming: TC lockup, 245/50-16 tires. If not locked up, maybe 200-300 slip, so 113-114.


Try this calculator:

http://murray.faithweb.com/formulas.htm#find_rear

 

Thank you very much!

 

I've got a vid of my gauges, and if I remember correctly at about 5500-5800 rpms I was doing 135+ ..I'll dig up the vid and double check, but it was way higher than 119.

I've got 3.73's, 17" wheels and an auto (obviously)

 

This should help;

Gear Ratio Link

 

With the stock size tires (25.5") I do about 123MPH at around 6,000rpm at the end of the traps with 3.73s.

 

Your speedo thinks you have 3.42's, I'll bet.

 

Nope, at the time, I had PCMFORLESS tuning...and he reprogrammed it for 3.73's. To make sure, when I got the PCM in, I had someone pace me at various speeds to make sure it was correct and accurate.

I cant upload the vid's, my webspace has been disabled by *** But at ~5300rpms I was doing ~135mph.

 

Fastbird93, That's a great link also!
The calculator says 119 mph. Which is right where I thought it should be.
I've got my 3-4 shift set at 120. But I haven't been able to test it out yet.
Thanks again guys!

 

You need 32 inch tall tires to get 135 @ 5300 rpm (no TC slip) in 3rd on an 4L60 or 4th in an M6. Stock tires are about 6 inches shorter. Perhaps your tach is a little off.

That pacing at 135 gets a little dicey, doesn't it?

 

Hmmm...wierd, well, cant say that I was getting paced at 135..but it would be fun to try!

I had a buddy hold the camera as I drove, and if anything, my speedo would be off instead of my tach. But its not, because I had gone to the track just the week prior and I would film my speedo and its was right on with the trap speeds on my slip.

Wonder what could be the kink...??

 

135 trap speed @ 5300? Nah, you didn't mean that, did you?

Seriously, if your speedo and tach are correct and you are using about 26 inch tires, or stock tires, 3.73's won't give 135 in third until 6600. 135 in 4th (OD) would be 4700 locked up or 5000-5300 depending on how loose you converter is. Obviously something isn't computing.

Try exactly 60 mph in OD with the TC locked up. 1900 = 3.42s, 2100 = 3.73s. That assuming 275/40-17 tires.

If you want to check the speedo, plug in cruise at 60 and time with a stopwatch for a measured mile. 3600 divided by seconds = mph.
At 60 mph, 3600/60 sec = 60 mph.

I'm still leaning toward 3.42s.

Good luck.

 

I'm going to go double check my PCM with LT1_edit, make sure all is set, then I'm gonna go for a drive and see what happens...maybe something is off.

Oh, and no, I didnt mean that my trap speeds are 135, I was referring that before I recorded the 135mph @ ~5300rpms, that weekend prior, I had gone to the drag strip, and my speedo was registering ~103-104 and my trap speeds on my time slip were about 103-104..so I knew my speedo was accurate.

Hmm, well, I'll find out whats going on here in a bit....thanks for the formula's.

-Alex

 

I think he means he's doing 135+ at that rpm going down the highway in 4th. Not going through the traps in 3rd gear on a dragstrip.