Differential and axle questions

[96blackcobra]

I am going to replacing my stock (broken) differential and axles in the next few weeks and need some suggestions on what to upgrade to.

I am also running 4:30.1 gears with a vortech v3 si. I am hitting the traps in 4th gear at almost redline. I am considering going down to a 4:10.1 gear. I will be adding a power pipe and a few other goodies this summer and hope to make 500 at the wheels. Would it be a good idea to go down to a 3:73, 4:10 or stay with the 4:30 and just shift to 5th??!?!?

Any input would be greatly appreciated.


Sam

 

[whtcobra1998]

do not power on in 5th gear. bad for the trans, just get 4.10's

 

[lafeva]

^agreed

 

[F8L BYT]

31 spline axles and diff, and 3.73 or 4.10's... Ditch those 4.30's... And like they said I wouldnt boost in 5th gear

 

[19Mystic96]

do not power on in 5th gear. bad for the trans, just get 4.10's

why's it bad for the trans?

 

[jumperjack]

why's it bad for the trans?

Motor

 

[96blackcobra]

I will be using the 03/04 cobra diff, but still need some advice on axles. Any suggestions?

I am considering just swapping in a t56 and staying with the 4.30's.

 

[19Mystic96]

Ford racing or moser axles will do fine for your setup...

 

[9804SNAKES]

I will be using the 03/04 cobra diff, but still need some advice on axles. Any suggestions?

I am considering just swapping in a t56 and staying with the 4.30's.

I put in the 03/04 diff, and went with FRPP 31 Spline axles and 3.73 FRPP ring and pinion. I also bought a FRPP complete bearing kit. Just a word, the guy who did my install had to shim my calipers as they were rubbing. I do have Power Slot rotors and the FRPP Axles are supposed to be factory replacements but I had some rubbing. Wasnt a big deal but I wasnt too happy about having to shim when axles were supposed to be direct drop ins. I did do some research and heard that when replacing axles, shimming the calipers isn't that unheard of, although FRPP's Tech line said I shouldn't of had too. Oh well.

 

[96blackcobra]

Thanks for the info!

 

[98cobraRx]

I put in the 03/04 diff, and went with FRPP 31 Spline axles and 3.73 FRPP ring and pinion. I also bought a FRPP complete bearing kit. Just a word, the guy who did my install had to shim my calipers as they were rubbing. I do have Power Slot rotors and the FRPP Axles are supposed to be factory replacements but I had some rubbing. Wasnt a big deal but I wasnt too happy about having to shim when axles were supposed to be direct drop ins. I did do some research and heard that when replacing axles, shimming the calipers isn't that unheard of, although FRPP's Tech line said I shouldn't of had too. Oh well.

I had to shim my calipers as well and I went with 31 spline mosers. So I guess it does not matter between the companies. I too have a 03/04 cobra diff. These are fairly strong setups not matter which axles you go with. As far as for switching gears, do the RPM calculation. 4th gear ratio I believe is 1.0 so going from 4.30s to 4.10s is going to be a slight drop. However this maybe just enough for you. Moral of the story check it on an RPM calculator. Also don't forget you can change tire size to drops RPMs at the track.

 

[goat-ee]

I will be using the 03/04 cobra diff, but still need some advice on axles. Any suggestions?

I am considering just swapping in a t56 and staying with the 4.30's.

You do not want to shift into 5th (or 6th) in the 1/4 mile, your replacing stuff anyway and the 4.30 is already borderline too steep according to you. The calculator says that a 4.30 @ 6500rpm will be going 115mph on 26" tall tires.

And to show top speeds in 4th gear @ 6500rpm with diff gears...

4.30=115mph
4.10=121
3.90=127
3.73=133

As you continue to upgrade that mph should go up, I would consider 3.90, but only you know your long term goals for the car.