My BRZ is Alive!! Upgraded Final Drive

[Chad_W]

To simulate going from 4.10 to 4.56 with just wheels and tires, you'd have to do a 215/40r16. There is a good option from Yokohama in this size and you'd also benefit from reduced rotational mass and unsprung weight. Unfortunately that's not a lot of tire in terms of ride quality and rim protection.

You're also going to lower your vehicle about 1", definitely a factor if you have other suspension mods. Lastly I'm not sure how great that will look in terms of overall circumference in the wheel well.

If you could get a hold of wheels and tires that size that fit just to try, it would be a great way to preview the benefits of the gearing change.

[DustinS]

I am waiting to see how you enjoy it with the turbo. That is the ultimate goal for my car.

[mrk1]

Originally Posted by DustinS

I am waiting to see how you enjoy it with the turbo. That is the ultimate goal for my car.

I know what exactly its going to do, the slight FD increase will give that sporty eagerness I miss in the car. The turbo will give the power! My new setup is a T25 GTX28 that should have no problem keeping up and flowing enough to match. Anyone who says turbos don't work with higher FD just didn't match up there setup.

[Toyota86.ir]

Originally Posted by Lunatic

I have the automatic and went with 4.88s. Best mod I have done to the car.
1 second off my 0 to 60 time
1.5 seconds off my 30 mph to 70 mph time.

How you measured 0-60 time? Cornometer? Obdii? Speedometer?
can you tell me the 0-60 times before and after swap?

[Lunatic]

Originally Posted by Toyota86.ir

How you measured 0-60 time? Cornometer? Obdii? Speedometer?
can you tell me the 0-60 times before and after swap?

With a Gtech SS meter
http://www.gtechpro.com/ss_fanatic.html

8 and 7 seconds.

[Toyota86.ir]

Originally Posted by Lunatic

With a Gtech SS meter
http://www.gtechpro.com/ss_fanatic.html

8 and 7 seconds.

Huge difference , 12.5% better time is awesome.
My record in sea level is around 6.6 (AT , stage 2 mike tune E85) With12.5% off i should record 5.86 seconds. Should be nice
My car swapped to 4.88 but i do not passed the break-in time.

[azynneo]

Originally Posted by mrk1

I got the gears from MFactory, $750.
Install kit with solid pinion spacer from Weir Performance $380.

I did the labor myself so that saves me money there as its not a quick job, setting up the backlash, pinion height and preload. There are a bunch of shims you need to set the back lash, this is really what makes this not a drive way install. I bought one of every size, not cheap. There are only 2 of these shims in the diff when its done but I had to try a few to get the back lash just right. If you have a shop do the gear set up they would have to have these shims.

Did you need to buy the install kit? Or could you have used your old stuff aside from the carrier bearer shims?

[mrk1]

Originally Posted by azynneo

Did you need to buy the install kit? Or could you have used your old stuff aside from the carrier bearer shims?

You absolutely need new parts, new shims, new bearings, new pinion spacer be it solid or crush. You can technically reuse some bearings but it's not a good idea for the amount of work here.

[azynneo]

Originally Posted by mrk1

You absolutely need new parts, new shims, new bearings, new pinion spacer be it solid or crush. You can technically reuse some bearings but it's not a good idea for the amount of work here.

welp, there goes 359$ extra bucks rip

[SUB-FT86]

Originally Posted by Toyota86.ir

Huge difference , 12.5% better time is awesome.
My record in sea level is around 6.6 (AT , stage 2 mike tune E85) With12.5% off i should record 5.86 seconds. Should be nice
My car swapped to 4.88 but i do not passed the break-in time.

I wonder if there is a method to figuring out how a 19% reduction fd ends up giving a 12.5% gain in acceleration. I wonder what a 5.29(29% reduction) would knock off.

[Toyota86.ir]

Originally Posted by SUB-FT86

I wonder if there is a method to figuring out how a 19% reduction fd ends up giving a 12.5% gain in acceleration. I wonder what a 5.29(29% reduction) would knock off.

Imagine AT 4.88 start from zero and in 55km/h the AT 4.88 shift to gear 2 .
AT 4.1 will be slower till 55km/h but from 55km/h to 65km/h the AT 4.1 is in gear 1 and AT 4.88 is in gear 2 and the torque of AT 4.1 is higher in 55-65km/h range.
This happen in all shifting range and overally FD 4.88 will not make it faster than 5% in 0-176km/h.
Going to higher FD will not help you.

[KoolBRZ]

Look up mechanical advantage. The 4.88 FD has a greater mechanical advantage in every gear than the 4.10 FD. This basically means the engine has more leverage to turn the tire, in every gear. measure the difference in FD with what you want, but the only measurement of any importance is measured by a stopwatch. A FD won't give you any more or less horsepower, but it will change the mechanical advantage the engine has in relation to the wheel/tire. This advantage can be measured with a stopwatch. It can also be measured by an accelerometer/smartphone app. You will definitely feel it.

[FRSBRZGT86FAN]

Originally Posted by stevesnj

Much more reliable and less expensive than any FI. Very simple and will work great with taller wheels and tires. Milage could suffer. Depends on the tire height and how you are on the skinny pedal.

you wouldn't happen to know anyone in NJ or PA that is reputable enough to do a quality final drive upgrade would you?

[bfrank1972]

Originally Posted by KoolBRZ

Look up mechanical advantage. The 4.88 FD has a greater mechanical advantage in every gear than the 4.10 FD. This basically means the engine has more leverage to turn the tire, in every gear. measure the difference in FD with what you want, but the only measurement of any importance is measured by a stopwatch. A FD won't give you any more or less horsepower, but it will change the mechanical advantage the engine has in relation to the wheel/tire. This advantage can be measured with a stopwatch. It can also be measured by an accelerometer/smartphone app. You will definitely feel it.

Yup, in gear acceleration will be harder, but shorter. As soon as the lower geared car shifts it loses it's advantage over the longer geared car (assuming both are in the upper power band). There's another thread on here somewhere where I discuss it in a bit more detail, and posted a spreadsheet that shows everything in basic mathematics. No doubt a lower FD makes the car FEEL more fun to drive though