4.10's...Problem for 1/4?

[SCalla1384]

Sup guys, I dont think Ive posted here yet, but have been browsing a lot. Very knowledgable forums.

I recentley added 4.10s to my GT. And their awsome. Can feel the pick a lot.

The other night I was messing around on the highway. I hit it pulliung on the on ramp. 4th Tached out pretty quick. So I did it again to see my speed. Around 5800rpm, I was only at 105mph.

Is that right? Ive heard its usally like 110-115mph at the top of 4th with 4.10's.

If I put my Prochamber on (have it just havent had the time to put it on), then I could be picking up headers soon. As the summer goes on Im going to do drag radials, K&N FIPK, 70mm TB, and Plenum.

Theres a good chance I could have to shift into 5th which would suck. I really would dread that.

Heres where something may come into play. Maybe the Speedo is messed up around higher RPMs? I bought a used Diablo Tuner, for the stock tune I tried to recalibrate the speedo. They only had 4.09, not 4.10. I did that, but for the stock tune it didnt work.
So I did a Diablo tune, the guy before me must have deleted all the tunes except that one, which is equivalant to a 91 Tune. So i did that, changed my gears to 4.09's (It didnt have a 4.10 or 4.1 option) Do you think possibly that has something to do with it? My speedo isnt off I dont think though, because I was doing 50mph and looked at my GPS and it said 50mph.

Thanks for any help guys, much appriciated.

 

[BurningRubber]

Nope, thats the end of 4th gear. It's around 110-115mph depending on tire size, and of course you can run a larger rear tire out back (28" drag radial is most common) to give some extra MPH to play with at the track.

With your mods, you will be fine with 4.10's at the track. You will be trapping below the redline, but close to it. Pretty much right where you want it.

If/when you start trapping 110+ mph, you have two options. Raise your rev limiter or run a larger rear tire. I notice your future mods include cams, so raising the rev limiter will probably happen anyway for you, since most cams like to spin higher RPM's to acheive full effects.

And although the tuner gives an option for 4.09, it is pretty much dead accurate to my knowledge. I've tested it on radar's that the police set out in the road, never been off. But thats not really higher speeds that i've tested.

 

[Stan Weiss]

4th gear (1:1), stock 245-45-17 tires, 5800 RPM, 108MPH

 

[Dark_Horse]

Gear Tables

 

[BlownStangGT]

Yeah until you get the cams and long tubes you will be fine running stock sized tire, 26", but once you get that stuff, you actually still might be fine bcaues you will be revving the motor higher with the cams, but you could go to a 28" tire for the track

 

[02nightmaregt]

Thats just the price you pay for a steeper gear bro. Unless your out highway street racing i don't see that as a problem

 

[SCalla1384]

Cool thanks for the help guys. Much appriciated. How much can I raise the rev limiter when I do cams? I dont want to blow the motor or anything. Thanks guys, very helpful

 

[Stan Weiss]

When you have it on the dyno getting tuned you will be able to see the shape of the HP curve. This will depend on the specs for the cams you install.

 

[COramprat]

My car is about at the peak of my HP curve right before the traps in the quarter at 103...so 110 to 115 at redline is normal.

 

[flstang65]

something else i noticed with my 4.10's was that i ran better with my stock suspension at the track than i do now with my lowering springs. even with the drag radials i get tons of wheel spin due to the terrible wight transfer, but she sure does carve up the corners though. im saving up for a suspension set up for the track, but i couldn't stand the 4x4 stance. lol. anyways, the rpm's you are experiencing sound all about right.

 

[joshheat25]

You'll be fine!