Manual Transmission Options for the IS300

Every single day, this question comes up – “what transmission to use when manual swapping my IS300” or something to that effect.  There are quite a few options, which is great.  Unfortunately, there is a lot of confusion and misdirection.  I’m going to clear that up in a single page.

First off, I’m sticking with common manual trans swaps, I’m sure someone will chime in with some crazy manual swap, but again, going by what is commonly available and will bolt up without too much issue.

Here’s the short list: w55 (stock 5 speed IS300 manual), w58 (stock 5 speed mk4 Supra NA), r154 (stock 5 speed mk3 turbo and some jdm cars), ar5 (solstice/sky 5 speed- also in h3’s and colorado’s but lots more work to fit), cd009 (Nissan Z and Infiniti G 6 speed), V160 (stock mk4 Supra turbo), and the t56/magnum (dozens of OEM and aftermarket applications).

There are a few important things to take into consideration when selecting a transmission – fitment, gear ratios, strength and price (I’ll let you research price)

Fitment

  • w55/w58 – bolts up with all stock components
  • r154 – use 1jz bellhousing, custom driveshaft
  • ar5 – use 1jz bellhousing, Verossa shifter housing, custom driveshaft (06 model years is the best option to purchase)
  • cd009 – adapter plates, custom shifter and driveshaft
  • v160 – custom driveshaft
  • t56 – adapter plates, custom driveshaft

Strength/drivability/repair/upgradability (hp and figures are commonly stated, not based on “my brothers cousin made XXX hp on his”)

  • w55 – weak but drives well (300-350 whp max)
  • w58 – marginal improvement over w55, drives well (350-400 whp max)
  • r154 – varied success – older versions drive like a dump truck, newer versions shift better and tend to be stronger – reports of failure range between 500 and 900 whp; almost all internal components are upgradable
  • ar5 – essentially a newer r154 that shifts much better – claims of breakage around 500-600 whp are common, though some have pushed over 800; many parts appear to interchange with upgraded r154 parts
  • cd009 – drives great, stout transmission, 800-1000 whp handling appears to be relatively common; very expensive upgraded gearsets available
  • v160 – used in 1000+ whp Supras very often – drives great, considered one of the best OEM transmissions money can buy; parts are discontinued through Toyota, many parts are being duplicated in the aftermarket
  • t56 / tr6060 / magnum – many variants of this transmission lineup with torque ratings anywhere from 350 ft-lbs to 1000 ft lbs, from the factory; many upgrades available enabling sequential shifting and heavier duty gear sets, capable of handling upwards of 2000 whp; shifts great

Gear Ratios

This is where most people go wrong with transmissions.  They see 6 speed as automatically better than 5 speed, but in some cases, shown below, its actually worse.  There’s a lot of math, but I’ll try to explain.

First, a spreadsheet of all of the transmission gear ratios (asterisks are for the 1:1 gear ratio)

W55 w58 r154 ar5 cd009 v160 t56 close t56 wide
1st 3.625 3.285 3.25 3.75 3.784 3.827 2.66 2.97
2nd 2.043 1.894 1.955 2.26 2.324 2.36 1.78 2.1
3rd 1.394 1.275 1.31 1.51 1.624 1.685 1.3 1.46
4th 1.000 * 1.000 * 1.000 * 1.000 * 1.271 1.312 1.000 * 1.000 *
5th 0.85 0.783 0.753 0.73 1.000 * 1.000 * 0.8 0.74
6th n/a n/a n/a n/a 0.794 0.793 0.63 0.5

For all of the MPH calculations below, I’m going to use a stock 6200 rpm redline with 25″ diameter tires (stock IS300 is 24.6, but many change to slightly larger diameter).  For cruise RPM, it will be top gear at 70 mph.  There are two stock rear differential ratios for the IS300 – 3.91 came in auto cars and 3.73 came in manual cars.  Tacoma 3.55 gear sets can be installed in the OEM diff carrier.  These three gear ratios are what I will use for my tables.  If you want to explore others, I use Apex Garage as it is a very easy to understand calculator.  Lower numerical ratios are available by modifying the subframe for different diff carriers, or installing a heavy duty 8.8″ rear.

Here are all of the 5 speed transmissions:

W55 w58 r154 ar5
diff: 3.91 3.73 3.55 3.91 3.73 3.55 3.91 3.73 3.55 3.91 3.73 3.55
1st 33 34 36 36 38 40 36 38 40 31 33 35
2nd 58 61 64 62 65 69 60 63 67 52 55 57
3rd 85 89 93 92 97 102 90 94 99 78 82 86
4th 118 124 130 118 124 130 118 124 130 118 124 130
5th 139 145 153 151 158 166 157 164 173 162 169 178
6th n/a n/a n/a n/a
cruise rpm 3150 3000 2850 2900 2750 2600 2775 2650 2550 2700 2550 2450

and the 6 speed transmissions:

cd009 v160 t56 close t56 wide
diff: 3.91 3.73 3.55 3.91 3.73 3.55 3.91 3.73 3.55 3.91 3.73 3.55
1st 31 33 34 31 32 34 44 46 49 40 42 44
2nd 51 53 56 50 52 55 66 69 73 56 59 62
3rd 73 76 80 70 73 77 91 95 100 81 85 89
4th 93 97 102 90 94 99 118 124 130 118 124 130
5th 118 124 130 118 124 130 147 155 162 159 167 176
6th 149 156 164 149 156 164 187 196 206 236 247 260
cruise rpm 2925 2800 2650 2925 2800 2650 2325 2200 2100 1850 1750 1675

So, that’s obviously a LOT of data.  Some things really stick out when you start looking at it closely though.

First off, some common misconceptions – 6 speed transmissions always give better gas mileage because they have 6 gears instead of 5.  The cd009 and V160 are almost identical and commonly talked about.  Notice their cruise rpm in their top gear is actually just a little lower than a w55 but higher than the other 5 speeds listed.

Common rule of thumb with manual transmissions is that if you are competing in some sort of straight line racing, you want to go through the traps in whatever gear is 1:1 as the overdrives (less than .99 ratio) tend to be smaller gears and are weaker.  Lets look at a car that should trap around 110 mph, typical of a low boost turbo kit’d IS300.  At stock redline, all of the 5 speeds will get it done with any of the available gear ratios and require three shifts to get there.  Same goes for both t56 variants.  The CD009 and V160, however, require getting into 5th gear for  110 mph, so one extra shift.  When starting to make the sort of power to trap 110, 120, 130 and more, in a manual transmission, getting off the line can be the hardest part.  A longer first gear actually makes it easier to launch a higher powered car.

Looking at the charts above, gear ratio wise, the cd009 and V160 are actually pretty poor choices for a stock rear end IS300, as they gain strength but gear ratio wise are really only good for low powered cars.  Medium to high powered cars will have difficulty putting the power down in low gears and excessive shifting will be annoying.

Lets look real close at the cars they came in.  The V160 in the Supra was paired with a 3.13 gear ratio.  This is a very good gear ratio combo.  Our 110 trap example above lets you cross the traps in 4th and cruise in 6th is 2350 rpm.  The cd009 in the Z cars was paired with a 3.55 gear ratio, which works ok with their 300ish hp engines.  Many in the Z groups complain about the short gearing when making more power than stock.  In a Supra, the cd009 would be a much better candidate to swap, where the gear ratios are well suited to stock Supra rear diff gearing.

Differential considerations:

  • W55 – works ok at stock power levels with stock 3.73 rear, 3.55 would be a nice upgrade though, especially if making 300-350 whp
  • W58 – nice gear ratios, usable with all three above listed diffs with moderate power levels
  • R154 – if you need medium power handling levels, this is a good option gear ratio wise, would be real nice paired with the 3.55 rear end, 3.73 works ok
  • ar5 – 1st through 3rd are on the short side, 4th is standard 1:1 and 5th is a nice overdrive – pair with 3.55, or, if available 3.43
  • cd009 – if you’re going with this transmission, hopefully you’re making some power to warrant it, but you’ll want to change rear diffs to low 3.xx’s to make it really good.  3.55 is really just barely livable given you should be making over 600 whp to actually want to go this route as the R154/AR5 are much better options for the medium power levels with respect to gear ratios and fitment.  One other note – the Z cars have a larger diameter stock tire, so that changes effective gear ratio a little as well
  • v160 – same as cd009 but substitute fitment issues for cost – this is by far the most costly transmission
  • t56/magnum – works well with high 3.xx gear ratios, so no need to change your rear diff until you start breaking it – if I was going manual in my IS300, it would be the t56

I hope this clears up some widespread confusion regarding the different transmission options for the IS300.

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