3.73'S Or 3.9'S

[ab_futura]

I can't decide on what diff gears I want. I'll be running a t56 from an 07 BF xr6 turbo and 18 inch wheels. How do I work out the max speed for each gear? What would be better for building boost on a T04z? I'm thinking 3.9's would make it spool really quick without making wheel spin too hard to control where as 4.11's would just make smoke.

What do you guys think?

[01txr]

I'm running 3.45 gears t56 BA sedan to4z with taz manifold,

Plazmamaman plenum, hdi GT series ic, 4 inch dump with progate 50 separate 2 inch wastegate pipe merge at bend just befoe going into x force single 3.5 system. Cat open to 4 inch exit as per standard x force 3.5.

Starts building boost in 6 gear 60kph think approx 1100 rpm making. From 100kph hits 17psi by 160kph.

I find it very responsive compared to oem setup,

I had orsm fuel Eco of 8.8l to 100k highway.

Little tricky to get off line would feel 3.73 ratio would be better to get off line with better Eco city with slightly hurting highway.

And lower you go the more easier control to get off line.

I don't think boost under load is going to differ a great deal as the weight of these falcons will still load up hard even with 4.1s.

As for speed in gears you need to measure tyre diameter work out circumference and multiply by gearing.

Tyre smoke will come down to quality of tyre and suspension set up.

I know mine running pedders extreme with Toyo proxy 4's 265x30x19 struggle

For grip 1st, 2nd when running 12 psi boost and useless 1st 2nd & 3rd when run 17psi boost.

Had nangkangs prior to the toyo's and they where like driving in the wet so bad I had

A ve ss beat me till 3rd before being able to peddle it and pass it.

The nangkangs where worst than the traction problems I have running 17psi on the toy's.

Also just to add on the gear ratios the to4z with it's early boost less lag than say eg gt45 that makes boost higher in the rpm will not suffer as much with tall gearing.

I'm not to concerned with the gearing as much as traction and the standard drive shafts

Breaking. Once I do the driveshafts run slicks then maybe running low gears will be of advantage to me.

Hope some of this is was helpful.

[ab_futura]

Cheers man. Your setup is very similar to what I've started to put together so that answers a lot of questions I've been asking. It's going into an EL xr6 and I'm going to get the diff rebuilt with a kaaz centre so naturally want to do diff gears at the same time.

[01txr]

Orsm.

Should be a rocket with the weight advantage.

Though a few times of doing same but just love every other aspect if the barra's.

However my son has just started working and what we have planned is ef el Xr for him to start off and either

Get another and slowly build doing same as you or what he

Really wants is to find a td cortina and fit barra turbo to it.

Since the release of the coyote I may get him to go that way as having the sweet sound of a sc v8 is the ultimate.

All will come down to if it's possible to squeeze it in and costs and being able to get it all.

I build a 351w td cortina a few years ago and he loved it and that's his main desire but it's finding one that's his main problem.

Good luck on your build, let me know how it turns out if you will as may be able to offer me s few pointers if we head that way too.