To shift, or not to shift...

[NA-Stang]

Ok, so I just installed 3.73 gears in my 05 Mustang GT. When I ran with my 3.55 gears, I was going through the traps in 3rd gear at about 6200 rpm at 109.57 mph. My shift points were at 6500 rpm.

Ok, now the tire size is large. It calculates to be 27.82" in dia.

So, my question is, am I going to need to shift to 4th now? I was under the impression that I was, until I started to do a little research.

With my tire size, at 6500 rpm, my trap speed calculates to 109 mph. Is that where I should be, or is that winding it out too much? I have read somewhere that you should be going through the traps at a certain percent above your shift points.

Would it benefit me to shift sooner, say 6200, to force my car to have to shift to 4th?

My mods are in my sig, with the exception of the 3.73 gears. I haven't changed that yet.

Any input would be geatly appreciated.

 

[Vapour Trails]

Would it benefit me to shift sooner, say 6200, to force my car to have to shift to 4th?

I highly doubt it.

According to my calculations, you can hit a maximum of 106 mph in 3rd gear with your combo of gears, tires and rpm. So you might have to shift into 4th.

 

[stkjock]

my calculator says 109 at 6500 with a 27.8" tire and 3.73

remember your trap is the last 66 feet, by the time you let out after the stripe you're going faster then your trap. You will have to shift to 4th, but cross the line around 5200-5300 RPM and leave a lot on the table

you may be better off going to a 25.5-26" tire and making better use of the power band.

 

[2012GT]

Just raise your rev limiter

 

[1fastpony]

You will have to shift to 4th. if your tire is 27.8 dia you will be taching ~6500 rpm at 99mph in 3rd gear. So to verify very easily just drive the car to say 75mph in 4th gear. If your tach reads ~3750 rpms then it should be on mark. Or, take the car to 99mph and check the rpms in 3rd...6500 rpms. You will though have to shift to 4th before the traps.

with 4:10 gears and 26" tire I shift to 4th just past the 1/8 mile mark and trap 5900-6100 rpm in 4th.

 

[minivanracer]

i say don't fear the gear

 

[Simon]

Just raise your rev limiter

Thats what I say. Raise it and dont worry about 4th.

 

[NA-Stang]

Thats what I say. Raise it and dont worry about 4th.

I have it set at 7000, so that's already taken care of. By my calcs, as I said earlier, 6500 should be 109 mph with my tire diameter. I think my first pass, im going to rev the piss out of her.

 

[1fastpony]

I have it set at 7000, so that's already taken care of. By my calcs, as I said earlier, 6500 should be 109 mph with my tire diameter. I think my first pass, im going to rev the piss out of her.

What size and type of tire you runing? 275/45/18-
BTW, operator error of the calculations I stated ealier. Forgot to change gears to 373, ooops.

Effectivley, and please correct if so, actually haven't changed the final gear ratio with that size tire very much. Maybe added some weight though?

 

[Agent007]

I say reduce your tire diameter to 26'' or bump up in gear to accomidate for the nearly 28'' tall tire! Good luck with your quest to quickness!

 

[NA-Stang]

What size and type of tire you runing? 275/45/18-
BTW, operator error of the calculations I stated ealier. Forgot to change gears to 373, ooops.

Effectivley, and please correct if so, actually haven't changed the final gear ratio with that size tire very much. Maybe added some weight though?

My tire size is 275/50R17

 

[gmantheman]

Leave it in 3rd. I also had 275/50/17 and 4.10s. I was able to trap in 3rd gear just over 6500. With that size tire, you should have went with 4.10s.

 

[NA-Stang]

Leave it in 3rd. I also had 275/50/17 and 4.10s. I was able to trap in 3rd gear just over 6500. With that size tire, you should have went with 4.10s.

Jesus christ! What was your et and mph?

 

[gmantheman]

Jesus christ! What was your et and mph?

My e.ts were only mid to low 13s and my traps were 103-105. The track conditions are usually not ideal. The D/A is usually 2500-3500 in the summer.
I found leaving it 3rd my ets dropped by about .3 to .5 and I gained 4-5 MPH.