Considering going to 3.727 gear/pinion in 6MT - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

HotLavaMan · 05-30-2012, 12:09 AM

Has anyone heard definitively that the rear diff is the same one as a Lexus IS250? I'm very interested in going from the 4.10 to the 3.727 gearing but don't want to waste money on a special order part that I probably would have a hard time returning if it isn't the correct one.

I'm trying to get lower RPM in 6th for highway cruising. Sure, I could just replace the gearing on 6th but that seems very expensive route to go. I don't think I'll mind making the other gears a bit taller.

Anyone know for sure one way or another? Other option is to try to order the JDM part from Japan as the GT86 has the 3.727 is an option.

Also : anyone know how if it's easy to adjust speedo for different ratio? Hopefully just a firmware setting?

Thanks

luxmn · 05-30-2012, 12:24 AM

sorry for thread jacking but may i ask why? is the gas saving that significant or is there other reasons that I miss? I'm surprised at the high gear in 6th myself but slowly getting used to being able to quickly pass car in cruise control without downshifting, i think they made this conscious decision to make it feels like a sport car.

Mitch · 05-30-2012, 12:26 AM

All of the reviews say this car is a hair under-powered as it is. Do you have your car yet? Have you driven it much on the highway? I thought my Civic Si revved absurdly high on the highway, but I got used to it quickly and the fuel economy was acceptable. That's another consideration: what's the payback period for the cost of swapping a differential vs the actual fuel savings you'd see?

coyote · 05-30-2012, 12:40 AM

It's a fair question and one that I reckon many who go forced induction will be asking.

HotLavaMan · 05-30-2012, 01:07 AM

I've got about 650 miles on mine. I find the current pickup adequate and don't mind down shifting to pass. My goal is simply to cruise at a slightly lower RPM (increase in gas mileage and decrease in noise). It's not bad as it is now and as you say, it's probably a long payback for gas savings to pay for it. I find the gearing a bit short from what I'm used to so that's why I'm looking into it.

Saibot · 05-30-2012, 11:10 AM

subscribed. im interested in this too

Jeff Lange · 05-30-2012, 11:57 AM

I can confirm the differential is the exact same as the IS300 and IS250.

Jeff

HotLavaMan · 05-30-2012, 12:19 PM

Quote:

Originally Posted by Jeff Lange

I can confirm the differential is the exact same as the IS300 and IS250.

Jeff

Awesome. Thanks much Jeff.

smbrm · 05-30-2012, 12:36 PM

3.727 would have been a much better compromise for the manual for street use. 4.1 appears to have been selected more for the track than the street.

With the 4.1, on the manual I believe you will be doing a lot of shifting in city driving in the 1-4 gears, while on the AT I believe you will be doing more shifting between 4-6 on the highway.

How big of an investment is an IS250 diff?

Jeff Lange · 05-30-2012, 01:12 PM

If you want to get a complete differential, you'll want one from the IS300 with optional LSD. IS250's do not have LSD.

IS300/250's come with 3.73 (MT) or 3.91 (AT) gearing, but only the IS300 has the optional Torsen T2 LSD that the FR-S/BRZ has.

Jeff

RYU · 05-30-2012, 01:28 PM

I reckon a lot of IS guys will switch to the 4.1 ratio.

I'm interested in this but was hoping to go the opposite on the AT. I'd like to go to a 4.4 or somewhere in the ballpark. If anyone has any info please share. Thank you!

SpeedR · 05-30-2012, 01:45 PM

Quote:

Originally Posted by RYU

I reckon a lot of IS guys will switch to the 4.1 ratio.

I'm interested in this but was hoping to go the opposite on the AT. I'd like to go to a 4.4 or somewhere in the ballpark. If anyone has any info please share. Thank you!

ya the auto could use lower gearing for better acceleration. I would do this in a second.

HotLavaMan · 05-30-2012, 01:48 PM

I spoke with my local Lexus dealer parts department. It's either a 41039-22010 or 41039-35010 and he's not sure which one would be the correct one. Price is either $172 or $197 and will take about a week to get here from central Lexus parts depot. So more research required.

Jeff Lange, do you have any suggestions on finding out which Lexus part number it would be?

smbrm · 05-30-2012, 01:54 PM

Quote:

Originally Posted by SpeedR

ya the auto could use lower gearing for better acceleration. I would do this in a second.

5th & 6th could be lower on th AT

05-30-2012, 12:09 AM	#1
HotLavaMan First 86 member Join Date: Jan 2012 Drives: FRS, Tacoma, Honda CB1100 Location: WA State Posts: 163 Thanks: 3 Thanked 91 Times in 28 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	Considering going to 3.727 gear/pinion in 6MT Has anyone heard definitively that the rear diff is the same one as a Lexus IS250? I'm very interested in going from the 4.10 to the 3.727 gearing but don't want to waste money on a special order part that I probably would have a hard time returning if it isn't the correct one. I'm trying to get lower RPM in 6th for highway cruising. Sure, I could just replace the gearing on 6th but that seems very expensive route to go. I don't think I'll mind making the other gears a bit taller. Anyone know for sure one way or another? Other option is to try to order the JDM part from Japan as the GT86 has the 3.727 is an option. Also : anyone know how if it's easy to adjust speedo for different ratio? Hopefully just a firmware setting? Thanks Last edited by HotLavaMan; 05-30-2012 at 12:10 AM. Reason: Added speedo question

05-30-2012, 11:57 AM	#7
Jeff Lange Senior Member Join Date: Dec 2011 Drives: 1986 AE86 GT-S, 2011 Lexus IS250 6M Location: Calgary, Canada Posts: 661 Thanks: 136 Thanked 361 Times in 161 Posts Mentioned: 5 Post(s) Tagged: 0 Thread(s)	I can confirm the differential is the exact same as the IS300 and IS250. Jeff __________________ 2011 Lexus IS350 F-Sport 6MT with LSD 1986 Toyota Corolla GT-S Supercharged

05-30-2012, 01:12 PM	#10
Jeff Lange Senior Member Join Date: Dec 2011 Drives: 1986 AE86 GT-S, 2011 Lexus IS250 6M Location: Calgary, Canada Posts: 661 Thanks: 136 Thanked 361 Times in 161 Posts Mentioned: 5 Post(s) Tagged: 0 Thread(s)	If you want to get a complete differential, you'll want one from the IS300 with optional LSD. IS250's do not have LSD. IS300/250's come with 3.73 (MT) or 3.91 (AT) gearing, but only the IS300 has the optional Torsen T2 LSD that the FR-S/BRZ has. Jeff __________________ 2011 Lexus IS350 F-Sport 6MT with LSD 1986 Toyota Corolla GT-S Supercharged

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05-30-2012, 12:24 AM	#2
luxmn First FR-S Join Date: Jan 2012 Drives: Whiteout MT FRS Location: austin tx Posts: 561 Thanks: 120 Thanked 125 Times in 83 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	sorry for thread jacking but may i ask why? is the gas saving that significant or is there other reasons that I miss? I'm surprised at the high gear in 6th myself but slowly getting used to being able to quickly pass car in cruise control without downshifting, i think they made this conscious decision to make it feels like a sport car.

05-30-2012, 12:26 AM	#3
Mitch form follows function Join Date: Nov 2011 Drives: RIP '13 BRZ Location: Baton Rouge Posts: 688 Thanks: 42 Thanked 234 Times in 122 Posts Mentioned: 7 Post(s) Tagged: 0 Thread(s)	All of the reviews say this car is a hair under-powered as it is. Do you have your car yet? Have you driven it much on the highway? I thought my Civic Si revved absurdly high on the highway, but I got used to it quickly and the fuel economy was acceptable. That's another consideration: what's the payback period for the cost of swapping a differential vs the actual fuel savings you'd see?

05-30-2012, 12:40 AM	#4
coyote Senior Member Join Date: Oct 2011 Drives: Slowly Location: brisbane.qld.au Posts: 1,064 Thanks: 212 Thanked 538 Times in 235 Posts Mentioned: 21 Post(s) Tagged: 1 Thread(s)	It's a fair question and one that I reckon many who go forced induction will be asking.

05-30-2012, 01:07 AM	#5
HotLavaMan First 86 member Join Date: Jan 2012 Drives: FRS, Tacoma, Honda CB1100 Location: WA State Posts: 163 Thanks: 3 Thanked 91 Times in 28 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	I've got about 650 miles on mine. I find the current pickup adequate and don't mind down shifting to pass. My goal is simply to cruise at a slightly lower RPM (increase in gas mileage and decrease in noise). It's not bad as it is now and as you say, it's probably a long payback for gas savings to pay for it. I find the gearing a bit short from what I'm used to so that's why I'm looking into it.

05-30-2012, 12:36 PM	#9
smbrm Senior Member Join Date: May 2010 Drives: Scion FRS Ht Lva(AT) Location: Alberta Posts: 409 Thanks: 30 Thanked 81 Times in 54 Posts Mentioned: 1 Post(s) Tagged: 0 Thread(s)	3.727 would have been a much better compromise for the manual for street use. 4.1 appears to have been selected more for the track than the street. With the 4.1, on the manual I believe you will be doing a lot of shifting in city driving in the 1-4 gears, while on the AT I believe you will be doing more shifting between 4-6 on the highway. How big of an investment is an IS250 diff?

05-30-2012, 01:28 PM	#11
RYU Senior Member Join Date: Dec 2011 Drives: really slow... Location: Los Angeles (SGV) Posts: 736 Thanks: 340 Thanked 253 Times in 145 Posts Mentioned: 10 Post(s) Tagged: 0 Thread(s)	I reckon a lot of IS guys will switch to the 4.1 ratio. I'm interested in this but was hoping to go the opposite on the AT. I'd like to go to a 4.4 or somewhere in the ballpark. If anyone has any info please share. Thank you!

05-30-2012, 01:48 PM	#13
HotLavaMan First 86 member Join Date: Jan 2012 Drives: FRS, Tacoma, Honda CB1100 Location: WA State Posts: 163 Thanks: 3 Thanked 91 Times in 28 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	I spoke with my local Lexus dealer parts department. It's either a 41039-22010 or 41039-35010 and he's not sure which one would be the correct one. Price is either $172 or $197 and will take about a week to get here from central Lexus parts depot. So more research required. Jeff Lange, do you have any suggestions on finding out which Lexus part number it would be?

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