All posts by Cody Graham

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)


  • 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.

Checking your Steering and Suspension Components – Lexus IS and GS specific

First off, the terminology I will use.  Some of these parts have different names, depending on who you ask or where you go.  I’ll try to be as generic as possible.

Ball Joint – a ball and stud joint that usually has a wide range of motion.  Usually used to connect control arms to steering knuckles

Control Arm – hinged link that connects the hub or knuckle to the chassis.  (Some parts have other names but also fall under the control arm definition)

Tie Rod – a ball and socket joint like a ball joint, co nnects the steering gearbox or rack and pinion to the steering knuckle for directional control.

Bushing – rubber, polyurethane or metal that is the interface between a control arm and the chassis – allows for flex and rotation


In the above picture, we have in blue the lower control arm, some refer to as LCA #1.  In Red, another lower control arm, LCA #2, also known as a caster arm or radius arm.  Orange is the lower ball joint, green is the upper control arm with integral ball joint, and in purple, the steering knuckle.  If they were pictured, the outer tie rod end attaches to the lower ball joint.

How to check it all.  All we need to check this stuff is a pry bar or similar substitute about 2-3′ long and a jack.  A friend to help is nice but not required, but most importantly, we’re going to need some common sense.

Ball Joints:  With the car flat on the ground, place a jack underneath the forward lower control arm, LCA 1.  Raise the jack until the tire is approximately 3-4″ off of the ground.  Now, using your pry bar, situate it underneath the tire and try to pry the wheel and tire straight up.  Here is where having a friend helps.  You need to see if there is any up or down movement in the lower ball joint as you are prying up.  Any movement at all calls for immediate replacement.  You can visually see movement, or, I like to put my hand on the joint to feel for movement.  While we have it jacked up this way, grab the wheel and tire at the 12 and 6 o’clock positions and shake it back and forth.  Look and feel for movement in the upper and lower ball joints.  Same goes here as earlier, any movement, replace it now.

Tie Rod Ends:  With the car jacked up as before, or from the frame, either way, grab the tire and wheel at 3 and 9 and rock it back and forth.  Feel the inner and outer tie rod ends for a light clunk.  An extremely small amount of play is acceptable, but if in doubt, change it out.  Movement here, any at all, will cause the vehicle to be out of alignment.  Even if the alignment machine says it is aligned, as soon as you drive the vehicle, the numbers mean nothing.

Control Arm Bushings:  The forward lower control arm is pretty reliable, but shake the wheel/tire at 12 and 6 with the car jacked up from the chassis (not the control arm as before) and look for movement.  The rear lower control arm is more difficult to test and you should just be looking for visually worn or torn bushings.  These are a common failure though they will never come apart completely, they just cause dynamic toe changes as you drive which causes an otherwise good alignment to exhibit bad tire wear.  Upper bushings, look for movement the same was as you did the forward lower control arm.


Here’s an example of a lower ball joint on an 1IS/2GS front suspension. The two holes on either side of the ball stud are where it mounts to the steering knuckle, the hole far left is for the tie rod end.

Lets Talk About Ball Joints on the IS and GS chassis – a quick rant

I see it all the time.  Someone posts a picture of one of their front wheels all laid back with the front fender dented in from it.  It usually has a caption that reads something like “What a POS, I was just driving along and my ball joint broke.

To be completely truthful, the way I read that is “I forgot to do some basic maintenance and inspections on my car, I want someone to feel bad for me.

Ok, so, ball joints.  Pretty amazing little piece.  They are responsible for supporting the steering knuckle (that the wheel bearing and ultimately the wheel itself) are bolted to, while it is turning, accelerating, braking.  It is undergoing all sorts of vertical, lateral and twisting loads.  Add to that, the suspension is designed for it to have one specific angle at rest, and then we lower our cars, which changes that angle.  This puts even more stress on the part.

Owners manuals.  Who reads those things?  Who on Earth would care to read the maintenance suggestions?  I’m here to tell you that there is some great information in there.  As much as I know about cars and I still sat down to read mine cover to cover for the GS I just bought.  The best part, I think, is where it says the car should be inspected, like, really inspected from time to time.  Every 30k miles or more frequently, actually.  Ball joints (and the rest of the steering/suspension components are listed, as well as pretty much every other mechanical item on the car.)

The good news is that these parts are relatively easy to change and even easier to test properly.  I will run down how to check the front end of a vehicle that anyone with a prybar and a jack can do.   That’s the next installment though, for now, here are some pictures of other cars that have had some ball joint issues.

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Making an A650 Transmission Survive on the Cheap – Part 3

Alright, so, we’ve talked about it and the theories behind how it works.  Now for some show and tell.


When you first remove the transmission pan, this is the first parts you see.  The grey thing in the middle is the screen.  Used to call it a filter, but it really doesn’t work that way anymore.  Circled in yellow is the pressure setting.  In this picture, it is turned up all the way.  It is normally in the middle setting.  To adjust, simply push in and turn.



Just a view without the filter or wiring in place.





This ball and the plastic piece / spring that comes with it is pretty important.  Make sure it goes back in.



Just a shot of the accumulators.




Here is a shot of all of the springs and accumulators and where they go.  Also pictured are my home made shims.

For the hard data, here is what you need to know.  I personally shimmed mine 12mm – yellow, 12mm – red, 15mm – green and 15mm – blue.  These shims were acceptable for daily driving with much firmer than stock shifts but not clunking in to gear.  Now that I’ve learned a lot more about these transmissions recently, I might have some ideas to make them more reliable still.  Also, it is very important to install the shims inside the aluminum pistons, not in the cylinder itself – doing this would block the fluid holes in the bottom.


Update: 5/12/2018, a couple local friends have documented this on video with some clarification as well:

RaceCar and Chill

IS300 Turbo Build


Dyno’ing your Automatic IS300 – the right way.

Dyno’ing a manual transmission car is easy.  For those with no experience on a dyno, the general idea is to get the tires rolling, slowly shifting up through the gears until you get to the gear that is closest to 1:1.  Most cars, this is 4th in a manual transmission.  Once rolling in 4th at about 2000-2500 rpm, you press start on the dyno and floor it.  Once you get to terminal engine speed (whatever you have chosen as max RPM), you let off, and the dyno slows down.

If you try flooring an auto trans car at 2000-2500 rpm, the car will downshift, no matter what gear you have selected.  Many dyno shops will simply floor it and let it run through the gears.  The problem with this is that you don’t get a good idea of the hp/tq curve below about 5000 rpm.  You will get peak HP and depending on turbo / engine setup, maybe peak TQ as well, but, like everything else we do on this website, there is a better way.

Our a650e automatics are 5 speed transmissions as well.  That in mind, the 4th gear is the gear we want to be in to dyno.  It is exactly 1:1, which is ideal.  So, follow these steps to get the most accurate dyno possible.  Select manual mode and downshift as far as possible using the steering wheel buttons – you will be limited to 2nd gear.  Put the car in snow mode.  Power mode will make no difference on the dyno.  Get the tires rolling, up to about 20 mph and upshift to 3rd using the steering wheel buttons.  You should feel it shift.  Slowly accelerate more to about 3000 rpm in 3rd.  Shift to 4th, you should feel it shift and the decrease in RPM.  Now that we are confirmed in 4th gear, slowly accelerate to 3200 rpm.  The dyno operator should hit the start run button at this point.  Floor it.  RPM will climb – be ready though, at 4000 rpm, you will want to turn off snow mode.  This is when the fun really starts.  Obviously, let off when you reach the maximum RPM you wish to achieve.

Why does this work, and why snow mode?  Simple – snow mode prevents downshifts except at very low RPM.  Even as low as 3000 RPM.  The downside to snow mode, and the reason we have to turn it off at 4000 RPM is that is also limits throttle open percentage to approximately 60%.  Won’t make much power that way.

So, now you know the best way to dyno your automatic IS300.

This also works on the road when using software to interpolate horsepower and torque, such as Virtual Dyno.

Fixing a jacked up car, AKA – the right way to wire a standalone, Part 1

This will be a multi part series as I just received the car yesterday and I am sure I will have more surprises along the way.

The enthusiast that dropped it off to me complained of poor drivability, inability to stay running when warm, excessively hard shifts, as well as just a lack of trust in the shop that performed the work initially.

Before I even got to drive the car, I started a basic inspection.  First thing I wanted to see was how the standalone (an AEM V1) was wired to the stock ECU.


2015-04-04 16.04.27

In all fairness, those are disconnected because I started trying to straighten up the wiring.  Before, it was a mess, no zip ties on common bunches, etc.  I decided after I first started that I needed to start documenting everything I found

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Yes, that is electrical tape insulating the connections to the stock +12v supply.

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Here, we have a resistor just kind of hanging out.  It is supplying resistance to the crank sensor, but I’ve never had to do that when running a standalone in conjunction with the stock ECU – in fact, the resistors need removed from the standalone in order to make it work right.  Further inspection is required.  Either way, the resistor is not insulated and is just chillin.

Ok, so, you’re thinking, this isn’t all too bad.  Well, the shop did not wire in intake air temp whatsoever.  Who knows why, but I knew that one of the first things I would need to do would be to add intake air temp.  The enthusiast who owns the car had already purchased and started to install, but became overwhelmed with the wiring.  Just when I’m thinking this isn’t all that bad, I decide to snip the ziptie holding the AEM in place under the drivers side of the dash.

2015-04-04 16.04.07

At this exact moment, my heart skipped a beat.  What I thought was initially going to be a quick and easy fix just became a mini-nightmare.  I decide I’m in it this far, lets inspect a little further.

I detached the mainboard from the case via the 3 screws underneath.  Yes, I said 3.  One was missing, as there is clearly supposed to be 4.

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Ok, so, this is scary, but what comes next almost made me cry.

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Speechless.  I had to sit down for a solid 5 minutes and decide which way to attack this.  I don’t like spending other peoples money, but this is so not right, on a ridiculous level.

Alright, so, first thing I had to do was to order the correct ECU plugs. This is an EVO9 plug n play AEM V1 30-1320.  For those that don’t understand that part in an IS300, well, we can use pretty much any AEM (I personally used to use the 30-6101 Supra box).  To make this right, I ordered the correct ECU plugs and pins from a cool EVO-centric website  I even ordered more pins than I would need, but you can see the order below.

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Just $48 (plus shipping) to avoid wiring this the worst way possible.

Just a quick list of other things I found that need to be changed:

1) MAF clamp – since the stock MAF is kept in the loop on these dual ECU setups, it needs to be clamped.  I’ve had good luck with a simple 4.2v diode.  This could be the explanation for the hard shifts, as the stock ECU uses MAF signal for part of its shift algorithm.

2) Intake air temp – this will be added.  I’m not sure how anyone expected a speed density setup to work without a proper air temp sensor wired in.

3) He was told it was running 18 psi, but it appears the wastegate spring is 12 psi.  There is a connection for a boost control solenoid, but there isn’t one installed anywhere on the car.

4) The GM MAP sensor appears to be a knockoff.  I’ve experienced these and haven’t had good luck with them at all.  Will require further inspection.

There may be more and I will update this as time comes.

Part 2 will be published once I’ve started cleaning up the AEM to be installed correctly.




Making the A650e transmission survive on the cheap.  Part 2

One of the most common misconceptions about the IS300 (and other cars that share the 5 speed Lexus automatic) is its ability to handle some real power.  In this article, I will outline what it takes to make it handle some power on the cheap, mods that almost anyone can do.  Everyones mileage will vary, no doubt, and part of its longevity rests with you, the driver, but this will be the best thing you can do without spending a ton of money.

There are a few theories on how to make automatic transmissions last.  I knew, going in, that my stock transmission might not last too long, so I was prepared to do some experimenting.  What I have ended up with is a transmission that was amazing at a 560 whp level (over 500 ft lb of torque also), and today, is still holding up to 650 whp, once in 3rd gear and above.  I have not modified the valve body in any way and the transmissions guts have never been removed.  The transmission pan and valve body will need to be removed, but that is it really.  How, you say?  Well, I did a bunch of research and found that it is a delicate balancing act to make these transmissions work right with some real power behind them.

The first problem I ran into was hitting the rev limiter under power.  Stock rev limiter is around 6200-6300 and the transmission starts its shift around 6100.  Doesn’t really give much time to do its thing, but it works just fine at the rather anemic stock power level.  There are two ways around this – raise the rev limiter or make it shift faster.

The best way without a full transmission build, and even without a valve body replacement is to modify the accumulators.  Accumulators are the small piston like devices that allow fluid to accumulate, in order to dampen shifts.  The springs need to be stiffer to make the shifts firmer, but they still need to be in place to maintain a little bit of shift damping.  There is no need to be chirping tires for a quarter throttle 2-3 shift.  I was never able to find good information on stock spring rate, or even find a good source for stiffer springs that would fit properly.  Instead, I simply shortened the space the spring could travel.  Unfortunately, I do not have measurements, as I simply did not take them when I was performing this mod 3 years ago.  Some day, I will pull her apart and get exact measurements.  To shorten the travel, I simply made bushings for the springs.  Anything metal that fits inside the accumulator will work.  I shimmed all 4 of mine approximately 15 mm.  That was attempt #2.  Attempt #1 was about half of that and though it helped, shimming more helped more, but is still not harsh.  There are small holes inside the accumulators that you do not want to block, but the a650 design prevents that to an extent.  One more quick mod related to this is to simply turn line pressure up.  On the side of the valve body, there is a pressure control – simply use a straight edge screwdriver to push in and rotate to the next detent.


here are the accumulators in an a340 circled – the a650 is extremely similar

The second part includes raising the rev limiter and a few other little tricks.  Even with the above listed modifications, getting the trans to shift too quickly will not be good.  At the power levels required for these types of modifications, hopefully you are running some sort of standalone already.  The 2jz is very capable of spinning higher than the stock 6300 rpm redline.  That redline is put there because the stock cams and naturally aspirated motor just simply don’t make much power past that.  We can safely spin a stock head / cams / valvetrain car past 7500 rpm, and probably higher than that if necessary.  I have my redline set up through the AEM Infinity I run at 7300 rpm.  One other thing I do is retard timing during the shift.  Since no standalone will control the auto trans, what I’ve done is drop timing to 0 at the shift point.  This reduces power just slightly (low timing keeps the turbo spooled though) until the lower RPM after the shift point is realized and the timing is obviously much higher there.  These mods are enough to allow my transmission to survive at 650 whp / 610 ft lb.  It doesn’t do so well in 1st and 2nd, mainly because the power comes on so strong, but once in 3rd, it holds together extremely well, all the way to redline in 5th.

Bad ideas – One of the most popular “mods” to these transmissions is the rods that go in the accumulators.  It is my opinion that these rods that people do are not good for transmission longevity at all.  The fact is, they make the transmission slam into gear pretty much every single shift.  This is not good on the internal components of the transmission.  Things like this are what causes the infamous sprag gears to roll over.  An instantaneous hit of power is much harder on the sprag than applying the power smoothly.  (Drop a hammer on a piece of glass versus lay a hammer on a piece of glass).

Good ideas – Don’t let the transmission slam into gear.  Use the transmission selector buttons to maintain the gear you want.  Prevent the transmission from downshifting if at all possible under full throttle.  If the engine is below 4000 RPM, applying full throttle will invoke a downshift, no matter what gear you have selected.  There is one way around this – the snow button.  If you have snow mode activated, you can go full throttle as low as 3000 rpm, but will be limited to 60% throttle until snow mode is turned off.

Making the A650e transmission survive on the cheap.  Part 1 – Cooling

One of the most common misconceptions about the IS300 (and other cars that share the 5 speed Lexus automatic) is its ability to handle some real power.  In this article, I will outline what it takes to make it handle good power on the cheap, mods that almost anyone can do.  Everyone’s mileage will vary, no doubt, and part of its longevity rests with you, the driver, but this will be the best thing you can do without spending a ton of money.

Part 1:  Transmission coolers – Keeping transmission fluid cool is one of the most important keys to transmission longevity.

The stock cooling system for the transmission lives in the lower portion of the factory radiator.  Fluid is simply pumped out of the transmission, through the radiator (you’ll notice two 5/16” hoses along the lower edge) and back into the transmission.  There is very little fluid pressure here – the return essentially falls into the transmission pan.  There is a factory temperature sender on the outlet of the transmission.  This can be monitored by obd2 scan tools with live data ability.


A wide variety of external transmission coolers exist on the market place.  You can’t have one too large, with regards to cooling, however, there isn’t a whole lot of space for large coolers without some ingenuity.  Many will simply attach to the front of the condenser, behind the intercooler (on a forced induction car).  Behind the drivers rear tire, there is some room for auxiliary coolers as well.  Some have fans as part of their design, some will add external fans.  No matter which you choose, it is a good idea to plumb the cooling system in such a way so that the fluid flows through the radiator based cooler first, then through the additional coolers.  This provides for the best chance for the fluid to cool before returning to the transmission pan.


My personal setup has transmission fluid routed through the radiator, then to the rear of the car.  Behind the drivers side rear tire, there is an unused space, away from anything else that produces heat.  Here, I have two transmission coolers stacked, with an 8” cooling fan on them.  Ideal transmission fluid temps are 175-225 degrees.  I monitor transmission output temp through the AEM Infinity, and when transmission temps reach 175 degrees F, 80 degrees C, the auxiliary cooling fan is turned on.  Sustained operation above 225 degrees will shorten transmission life, and any operation above 240 degrees is extremely detrimental, as the fluid itself begins breaking down.

20140901_211627(excuse the poor picture and dirty shield)  

A few key things that everyone needs to know with regards to this.  First off, make sure any fluid lines used are rated for transmission fluid.  More commonly available at parts stores is fuel injection hose, which will break down over time when used with transmission fluid.  It is a good practice to use high quality fuel injection hose clamps instead of the more traditional worm gear clamps.  I can’t say this is all I’ve ever used, but these are stronger, provide more consistent clamping pressure and once you use them, you will understand why I advocate for them.  Next on the list is fluid type.  Toyota T-IV fluid is the only transmission fluid to be used in most Toyota transmissions.  It is relatively inexpensive at the dealer and it works great.  Many manufacturers do make generic import transmission fluids that will work, but in general, they are the same price or even more expensive than the genuine fluid.  Last but not least, no amount of cooling will help if you are are hard on the transmission and do high powered pulls and races back to back.  Monitor temperature and allow the fluid to cool if it is getting unnecessarily high.