|
Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain. |
|
Thread Tools | Search this Thread |
02-27-2017, 09:38 PM | #1 |
Senior Member
Join Date: Oct 2014
Drives: Asphalt build in progress
Location: United States
Posts: 118
Thanks: 6
Thanked 96 Times in 28 Posts
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
|
Installed 3.91 rear diff from Lexus is300- amazing
I just swapped out my stock 4.10 diff for the 3.91 harvested from a Lexus is300. The difference was profound.
I have a Ptuning turbo kit with e85 and it dyno'd at 430whp. Fast as hell. I have the Clutchmaster RX300 clutch. I love the car but I've never really been happy with how choppy it felt. Not terribly smooth engaging 1st gear, and when I'd lift off the gas there was a noticeable deceleration. I'd also find myself wishing there was a 7th gear, as I'd be at 3000 rpm at 70mph. After doing some research I learned the diff swap from the Lexus was pretty much a bolt on. I figured I would give it a shot. The result : Awesome in every respect. The caveat is- this only applies to boosted 86's not NA. With the new diff the car is slicker than snot in first gear, super easy to drive in town, I can stay in each gear longer so the turbo spools up better, and at 76mph I'm at 3100 RPM. For me, the is the missing link. The car just glides, super smooth delivery of power, and wicked fast without the nervous and choppy feel of the lower gear ratio ( 4.10) I'm a happy dude. |
The Following 13 Users Say Thank You to ogrowup For This Useful Post: | DIE1000DEATHS (02-27-2017), flippy (04-12-2022), funwheeldrive (02-28-2017), jcw99 (08-30-2019), jeepmor (05-11-2022), kmbkk (06-29-2020), R2 (02-27-2017), skylinekin (03-02-2017), Teseo (02-27-2017), ThatAsianBradah (02-12-2018), Tristor (09-18-2019), twag4 (02-27-2017), zc06_kisstherain (02-28-2017) |
02-27-2017, 10:10 PM | #2 |
Senior Member
Join Date: Mar 2013
Drives: Sterling BRZ Ltd
Location: New England
Posts: 1,702
Thanks: 403
Thanked 1,389 Times in 671 Posts
Mentioned: 20 Post(s)
Tagged: 2 Thread(s)
|
I never looked back when I made the swap.
__________________
|
02-27-2017, 10:27 PM | #3 |
Senior Member
Join Date: Feb 2014
Drives: White 2014 BRZ
Location: Orlando, FL.
Posts: 519
Thanks: 131
Thanked 155 Times in 109 Posts
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
|
Can we go even lower to say 3.7? Although a lower FD I think theoretically puts more stress on the trans/gears.
__________________
JDL Turbo kit - Ecutek, HRI tuned.
|
02-27-2017, 10:29 PM | #4 |
Senior Member
Join Date: Mar 2013
Drives: Sterling BRZ Ltd
Location: New England
Posts: 1,702
Thanks: 403
Thanked 1,389 Times in 671 Posts
Mentioned: 20 Post(s)
Tagged: 2 Thread(s)
|
3.73 is possible but harder to come across then the 3.91
__________________
|
02-28-2017, 07:00 AM | #5 |
Senior Member
Join Date: Jul 2015
Drives: Late 2014 Subaru BRZ
Location: Cape Coral, FL
Posts: 557
Thanks: 20
Thanked 183 Times in 139 Posts
Mentioned: 5 Post(s)
Tagged: 2 Thread(s)
|
Throw this out there. But a vendor on the forums does offer such a service and the price after rebuild, knowing its going to hold together is well worth it.
Link to the site is below. http://www.spencerfabricationcompany...rive-upgrades/
__________________
2014 Subaru BRZ
FBM Turbokit: GTX3076R - ECUTEK HRI FlexFuel tune - FBM 3" Turboback Exhaust - 550cc Injectors - Walbro 485 Fuel Pump - 4bar Map Sensor - FBM Oil Pan - ACT SB7-XTSS - AMSOIL all fluids - Forester XT Oil Cooler - Cusco engine, trans mounts - Whiteline rear differential bushings - Perrin shifter bushing - Firehawk 235/45/17 - AEM Failsafe |
02-28-2017, 08:18 AM | #6 |
Senior Member
Join Date: Oct 2014
Drives: Asphalt build in progress
Location: United States
Posts: 118
Thanks: 6
Thanked 96 Times in 28 Posts
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
|
I bought my diff from Spencer. He's a good guy, and very knowledgable. I did however get the impression he is scaling back his operation...
|
02-28-2017, 10:46 AM | #7 |
Senior Member
Join Date: Mar 2016
Drives: Stock
Location: Arkansas
Posts: 206
Thanks: 52
Thanked 48 Times in 33 Posts
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
|
I haven't done this swap! Just making that clear first! But I decided to go with a meatier tire. Add about an in to the circumference. This in effect lowers the final drive too. So I suggest to anyone who doesn't want to do the swap or at least see how it feels? This could be a good option. Just pick up a cheap used set of tires. Also let's say you already did the swap and want it lower even still just add a meatier set of tires! As for me I will say the ride and take off is a lot smoother and not so jarring.
|
02-28-2017, 11:08 AM | #8 |
Senior Member
Join Date: Jan 2014
Drives: BANNED FOR TELLING THE TRUTH
Location: MODS ARE ON A POWER TRIP
Posts: 3,447
Thanks: 7,830
Thanked 3,022 Times in 1,409 Posts
Mentioned: 38 Post(s)
Tagged: 1 Thread(s)
|
Why does this only apply to boosted 86s?
|
02-28-2017, 11:12 AM | #9 |
The Gunshine State
Join Date: Aug 2016
Drives: '14 BRZ Limited
Location: Florida
Posts: 1,463
Thanks: 631
Thanked 1,163 Times in 587 Posts
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
|
For boost, you generally want longer gear ratios in order to build up boost.
For NA, you want shorter gearing for quick acceleration and keeping the RPMs high between shifts.
__________________
Current DD: M235i |
The Following 3 Users Say Thank You to 8RZ For This Useful Post: |
02-28-2017, 11:42 AM | #10 |
Senior Member
Join Date: Jun 2015
Drives: BRZ. R34 GT-T
Location: Calgary
Posts: 762
Thanks: 737
Thanked 613 Times in 302 Posts
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
|
My cars just going in to the shop to get boosted and built engine to put down 400+.
I was wondering how I was going to manage first gear with that much power. With the stock gear set and the power you had was 1st gear even usable ? What speed does first gear top out at with your new gear ratio? compared to stock? Cheers and thanks for your thoughts and experience.
__________________
/ SARD / ENKEI / GREDDY / RACESENG / CUSCO / PERRIN / KW / POWERED BY MAX / SPARCO / STOPTECH / BREMBO / ROCKET BUNNY / FULL-RACE twin scroll / OS GIKEN / WHITELINE
|
02-28-2017, 11:52 AM | #11 |
Senior Member
Join Date: Jul 2013
Drives: 08 4x4 offroad tacoma/ raven fr-s
Location: Memphis
Posts: 143
Thanks: 3
Thanked 13 Times in 11 Posts
Mentioned: 1 Post(s)
Tagged: 2 Thread(s)
|
It's my understanding that the FRS, IS300 and MKIII supra diffs are all interchangable. The supra diffs have a 3.73 option as well as a 3.91
|
03-01-2017, 06:40 AM | #12 |
Project Shadow
Join Date: Mar 2015
Drives: 2015 BRZ Limited 6MT
Location: Menifee, CA
Posts: 516
Thanks: 663
Thanked 311 Times in 186 Posts
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
|
Yeah, i have an is300 3.73 final drive in mine.
__________________
|
03-01-2017, 07:04 AM | #13 |
Senior Member
Join Date: Mar 2013
Drives: Sterling BRZ Ltd
Location: New England
Posts: 1,702
Thanks: 403
Thanked 1,389 Times in 671 Posts
Mentioned: 20 Post(s)
Tagged: 2 Thread(s)
|
Only the guts of the MK3 supra can be swapped into a BRZ or IS300 case then mounted in the car. The MK3 case uses different style mounts.
__________________
|
The Following User Says Thank You to mrk1 For This Useful Post: | jcw99 (08-30-2019) |
03-01-2017, 08:25 AM | #14 |
Senior Member
Join Date: Oct 2016
Drives: '14 Monogram, '95 Miata, '90 300ZX
Location: VA
Posts: 378
Thanks: 499
Thanked 253 Times in 144 Posts
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
|
Higher power levels mean that your first gear or two end very quickly so you have to shift much sooner, and the potential to break the tires loose is a lot greater. I've driven some boosted or v8 swapped cars that originally came NA with really high rear end ratios where this happens, and it can be quite annoying. The usual fix is swapping in a diff with a lower ratio. |
The Following User Says Thank You to Yardjass For This Useful Post: | jeepmor (05-11-2022) |
|
|
Thread Tools | Search this Thread |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
IS300 M85/M98 rear diff - does it fit? | PantsDants | Engine, Exhaust, Transmission | 39 | 03-28-2017 08:28 PM |
Lexus is300 diff swap M98 3.91 | ogrowup | Engine, Exhaust, Transmission | 5 | 02-28-2017 10:45 AM |
Lexus IS300 Second Car - Thoughts? | somecrazyazn | Other Vehicles & General Automotive Discussions | 48 | 05-05-2014 05:47 PM |
vs Lexus IS300? | SteelReign | FR-S / BRZ vs.... | 38 | 03-27-2012 11:48 AM |