KahnBB6

iTrader: (5)

I live in L.A. and currently do not feel that it's worth it to spend a small fortune to NA-T or 1JZ/2JZ/USDM swap my DD car or deal with the unpredictability of smog or roadside hood pop... I am interested in changing from my stock 4.08 to 4.27 gearset for an incrementally small performance improvement.

I would be doing this along with a TT Auto LSD or TRD 1.5 swap.

I've searched but haven't found much of anything regarding these questions:

1) What 10-bolt Toyota/Lexus cars came with a 4.27 gearset?

2) Must I use the pinion as well as the 4.27 gear? (I've never swapped a rear end before)

3) Has anyone run 4.27 gears on a non-turbo 2JZ-GE 5-speed? I know the improvement in acceleration will be minor (not to mention the speedo being off, losing some max top end and gas mileage) but I'd like to know people's impressions if they have tried it.

account2x

iTrader: (5)

1) SC300 auto differential from a junkyard
2) Swap out the whole differential/case
3) You are already about 3K rpm @ 65mph correct? 6% increase will be just under 200rpm increase. Unless you never hit 5th gear the reduction in mpg wouldn't be worth the increase in power. If It was me I would swap out to the SC400 3.92 differential for the increase mpg.

xspsi6

iTrader: (31)

It will liven up the gear box and make it more fun but yea mpg's would go down but if you can live with that I say go for it.

GS FONZy

iTrader: (6)

You will gain nothing by doing this. The SC does not have enough power to make a noticeable difference. First gear is alredy short and powerless, imagine how much shorter it will be now.

KahnBB6

iTrader: (5)

Thanks guys. For gas mileage it seems like it's going to be an extremely small decrease. I feel like the stock 5-speed non-turbo drivetrain would suffer in the fun department if I were to go with a 3.92 or 3.77 gearset. Getting the RPMs down would be good if I had boost but I don't and may not ever go that route.

I didn't know the automatic SC300's came with 4.27's. That makes picking up an entire diff for an LSD swap very easy.

In playing with the gear ratios for an R154 transmission it seems on paper like I'd gain most of the the top speed and lower rpms back when using the 4.27 ratio.

account2x

iTrader: (5)

You believe that going to a 4.27 would increase the fun. It will not. The engine is too weak for a differential swap to give a noticeable increase in power but enough to give a noticeable decrease in mileage.

KahnBB6

iTrader: (5)

I used this calculator:

http://www.240edge.com/performance/top-speed-calc.html

and these wiki's to obtain W58 and R154 gear ratios:

http://en.wikipedia.org/wiki/Toyota_W_transmission
http://en.wikipedia.org/wiki/Toyota_R_transmission

It seems like the difference in first gear is 1-2mph. I would imagine it would feel even shorter from a seat of the pants perspective. My 5th Gen Prelude's first gear was so short it was useless if the car was at anything other than a dead stop. I'm used to that.

Even if the performance benefits are negligible I see the main benefit being that (since I am not going turbo) I can obtain a whole Auto differential very easily and drop it off to a professional shop to install an LSD and set proper backlash (which I am not set up to do).

That makes swapping an LSD diff into my daily driver much easier since there will be minimal downtime.

All said, I'm not expecting blistering performance with a 4.27:1 ratio, just a small increase in acceleration and going through the gears faster. If I had an SC400 with their MUCH milder ratios I'd never consider a 4.27.

KahnBB6

iTrader: (5)

Changing gear ratios doesn't increase or decrease power but it does change the delivery of the engine's powerband.

Based on the figures I'm seeing, the RPM vs MPH changes aren't going to be that drastic. These cars already get terrible gas mileage most of the time anyway and a 1-2mph difference with a slightly shorter rear end doesn't sound like it will take anywhere near 5 mpg more in mixed driving. Maybe 1-2mpg at most?

Even so, with the gearing being shorter I'd think I could get out of gears 1-3 *only slightly* sooner and spend less time lumbering up to 45mph before working my way to 5th gear.

This is a 3400lb long wheelbase car with a 225hp engine that doesn't begin to come to life until 4000rpm mated to a slightly lazy 5-speed manual transmission. I'm not expecting miracles.

account2x

iTrader: (5)

You flooring at every stop light to beat out that other 3500lb 180hp car by a few inches? Once in 5th you will be using more gas for nothing. With the 3.92 you might get 1-2mpg more and that could be close to 10% with how bad the mpg is already.


I did these quick calculations.

4.273
4.083
3.916

215/60-15

40mph lowest in 5th.
1788
1709
1639

65mph highway speed
2906
2777
2663

80mph speeding
3576
3417
3277

8% drop in gearing with the sc400 gearing over the sc300 auto gearing. The car isn't going to be fast without a turbo. Why not optimize for better cruising?

KahnBB6

iTrader: (5)

I don't floor it at every stoplight and I do not race other cars. I just enjoy driving the car and occasionally take it on mountain roads. With a 3.92 the car will feel even slower than it does already and will take even longer to go through the powerband despite gaining a tiny bit of gas mileage. How is that an improvement?

I can completely understand the logic of NA-T, 1JZGTE and 2JZGTE guys swapping to 3.92 or 3.77 ratios for 5-speeds or 3.26 ratios for 6-speeds but there you can fine tune the engine's output to make up for longer gearing that would otherwise allow for better gas mileage off-boost.

I'm not in the boost boat, however.

I am not currently running a 4.27 gearset. I am running the stock 4.08 gearset that came with my car since it's an original 5-speed. Also, although my car is a daily I did not buy it to just cruise around and never push it for my own enjoyment. With the 0-60 performance of the car being what it is to begin with, why would I want to diminish it further by going to a 3.92?

Gaining 1-2mpg and having slower acceleration with a 3.92 seems about the same tradeoff as losing 1-2mpg and having *slightly* faster acceleration with a 4.27.

I'm already in the middle of those two choices with a 4.08.

xspsi6

iTrader: (31)

I did this first hand about 3-4 years ago in my 5spd sc300 and the car was much more fun to drive as it was as if you were driving a close ratio gear box but I ended up taking out the diff because I was driving on long trips and wanted the mpg's but it for sure makes the car fun around town from stoplight to stoplight!

lev00221

iTrader: (28)

I originally had an SC300 NA-T with the Boostlogic Auto. I had a W58 swapped in and left the original 4.27 rear end in place. Great off the line but I couldn't stay in boost for very long before hitting the redline. Also, cruising at 70 mph at 3000 rpm wasn't much fun.

Nonetheless, the rear end swap is so easy and so inexpensive that I think that you should try it and see what you think. If you hate it, switch it back.

Incidentally, about a month after getting the W58 I changed to a v161 and 3.26 rear end. It now feels like a totally different car.

Good luck!

KahnBB6

iTrader: (5)

Thank you for your response! I understand that if I choose to use a 4.27 I will be trading off a little fuel economy but I am glad to hear that there actually is a seat of the pants difference in normal driving. That's all I'm looking for!

Well, that and an LSD swap at the same time.

Thank you! Boost changes my entire reason for creating this thread and renders the 4.27 and possibly even 4.08 stocker moot. I'd love to play that game and I'm sure it's worth it in the end but now isn't the time for me. I'd never boost with the W58 anyway.

I was used to cruising at around 3,000rpm in 5th gear at 70mph in my last car. It's not ideal for fuel economy but I knew this car would have poor gas mileage when I bought it.

And I absolutely can swap back to stock should I choose to. I plan to keep the 4.08 as long as I have the car.

Out of curiosity, can you describe the feeling of the V161 and 3.26 versus the old 5-speed?

BAD954BOI

iTrader: (5)

Sorry not trying to thread jack just want to make sure i have the right mind set

I have a sc3 with a r154 conversion with the stock 4.27 rear end and i'm not going to lie the gears are SHORT!!! i'm looking to swap out the diff with a lower gear ratio at the moment i have a 4.08 at my boys shop waiting to be opened and counted for reinsurance but when i do the math in my head i dont think it's going to be that big of a difference plus it's still not lsd... so i started looking into the mk3 supra turbo lsd diff that is i think a 3.90 which i would swap into my auto diff since the 4.08 is in higher demand.

(does this make perfect sense or is the sc400 diff lsd and a 100% drop in with out mods making it the easiest route?)

-thank you

KahnBB6

iTrader: (5)

No worry about the thread. I have to ask: if you've got an R154 does that mean you've got a GTE swap or NA-T kit on your SC3?

From what I do know:

-- Soarer 2.5GT 5-speed manuals came with a 4.08 LSD rear axle against the R154 trans. Using the gearset you have waiting would technically get the car closer to the way Toyota built them overseas, however as many in this thread have mentioned if you are running boost it's a popular choice to get an even lower ratio to help with gas mileage as well as gearing. My original questions in this thread assumed a 2JZ-GE stock engine with NO boost, hence the 4.27 argument.

-- To my knowledge, MKIII Supra rear ratios and LSD's do not fit SC300/400 10-bolt pumpkins. Your LSD options are: 93-98 Supra Twin Turbo Automatic Torsen LSD (only an option on 97-98 TT Autos), or any LSD made for 93-98 Supra TT Automatic cars because the rear carrier is 10-bolt just the same as the SC300/400.

-- No SC300's or SC400's ever came with factory LSD's standard or as an option. JDM Soarer 2.5GT's had them as options. Unless you swap in a Supra TT Auto LSD rear pumpkin (3.769:1 rear ratio) you must have an LSD installed into your 10-bolt pumpkin of choice.

Hope this helps and anyone please feel free to correct any misinformation on my part.