Final drive higher or lower for auto turbo?

[tomm.brz]

Ops sorry, while typing i forgot OP is boosted, was thinking somehow he was NA still

anyway still not enough from him to enjoy 5th gear, apparently that is his goal
So would benefit with a 4.56 fd

[ZDan]

Still gonna have the same gap between 4th and 5th ratios even with 4.56 diff, you'll just experience it at a lower road speed for a given shift point.

Too bad the AT has such a wide 4-5 gap, should be more like the MT where you keep 5th gear closer to 4th and then have a wider gap 5th to 6th gear for lower-rpm and higher-mpg for highway cruise.

Only solution is to hold it in 4th longer before upshifting. Upshifting at redline you'll land at 5276 rpm in 5th, shouldn't be a problem with TORBO!

[Dzmitry]

Originally Posted by Lucky21

Hmmm if you drive mt try to imagine going from 4th straight to sixth gear, that what I meant by 5th gear being sluggish and almost unusable even if i'm boosted. It's like for example I can reach 130mph in 4th gear that probably as high as i'm going to get as the moment I shift into 5th it just bogs down due to the long gears. So I just thought maybe a higher final drive would act like a shorter 5th gear or it would be better to go lower so I can make the most out of 4th gear totally disregarding 5th.

I know most people here don't really care about top speed but I was just genuinely curious if you could adjust that as I live in an area where such speeds are achievable legally (for the most part) Hope my post doesn't confuse others sorry.

Then based on that statement, you definitely want a higher FD, like 4.56 or more. You're talking about acceleration then, not a top speed. A higher FD will give all your gears more torque and make gears like 5th and 6th shorter, so they feel quicker.

[Dzmitry]

Originally Posted by ZDan

Still gonna have the same gap between 4th and 5th ratios even with 4.56 diff, you'll just experience it at a lower road speed for a given shift point.

Too bad the AT has such a wide 4-5 gap, should be more like the MT where you keep 5th gear closer to 4th and then have a wider gap 5th to 6th gear for lower-rpm and higher-mpg for highway cruise.

Only solution is to hold it in 4th longer before upshifting. Upshifting at redline you'll land at 5276 rpm in 5th, shouldn't be a problem with TORBO!

Yeah, in the end, the guy clearly likes power and the sensation of acceleration. Because I'm plenty satisfied with my 5th gear on headers+E85 on a tune. I could only imagine the massive difference on 300whp lol.

[Lucky21]

Found this on youtube. It seems the higher fd does give 5th more acceleration

[Dzmitry]

Originally Posted by Lucky21

Found this on youtube. It seems the higher fd does give 5th more acceleration

Right, it absolutely does, as there is more torque to the individual gears with a higher FD ratio. Math will dictate this. The losses you will have is more shifting in the same period of time, higher RPM in cruising gear, and lower mpg. You can see in this comparison video, as well as others out there, that there is little to no difference of actual results in terms of how much faster you get up to a certain speed. This is mostly attributed to the fact that you have more shifts involved. But purely in terms of acceleration PER gear and FEEL, each gear will be and will feel faster with a higher FD.