Trans Cooler Towing

[rjstokes]

Hi all,

We've got a Fortuner which I believe have the same running gear as the new Hilux. Wondering if anyone has any comment on aftermarket trans coolers when they are used for towing. We'll be pulling a 2.5t ATM van with ours and I've always had a larger tranny cooler fitted. Given this car is new though, with warranty complications, figured I just leave it stock and if it goes bang - it'll be covered on warranty. Thoughts?

[Gulfstream8]

Hello rjstokes and welcome to the forum.

The old 4 speed auto in the previous Gen 7 Diesels (unlike the Gen 7 V6 with the far superior 5 speed A750) was an antique plagued with problems. Your new Fortuner gets a new far superior Auto to cope with higher torque and towing.

At 2.5 your well within the limits of its capabilities. If it were my money and I had any concerns I would purchase a Scan Gauge and check the Transmission temp while driving unloaded and loaded and then make a call.

2 Reasons
The A750 in my Lux from my experience has a critical operating temp range - and that's both cold and hot. What I can tell you is that it's amazing how stable that temp is and Toyota did that for a reason and running an external cooler could interfere with that.

The second is why spend money or fix something that's not broken.

Once again if it were my money I would service it and change the oil and oil strainer at 100k rather than an oil cooler as I find this more important. I'm unsure as it's such a new unit (your Fortuner) but Toyota was so confident of the A750 they made it a sealed unit. I'm unsure if Toyota has made the Gen 8 Autos a sealed unit but if so maybe implement a service at 100k.

[ktm300]

Excellent advice .

[HK1837]

I installed a transmission temperature gauge (from Wholesale Automatics) on my 2011 SR5 with A750F 5spd auto. Even towing an empty box trailer the gauge showed 100deg. I put a Wholesale Automatics cooler in series with the radiator cooler, even towing with my box trailer fully loaded (1540kg) it rarely sees 75deg. With the car trailer and a Monaro or Holden ute on it (2250kg) on a stinking hot day it barely sees 100deg.

I would never tow without an oil to air cooler, the lower the fluid temperature the better.

A750F isn't exactly sealed, you can change the oil with the right gear.

If I were you i'd talk to Rodney at Wholesale Automatics for best advice on a cooler for the newer Hilux auto.

[Gulfstream8]

Opps sorry HK1837 yes I should have been more clear the A750E and A750F are classed as a sealed unit by Toyota ie "oil and oil strainer for life of vehicle" but you are correct it most certainly is serviceable and as such I change both at 100K.

Question HK1837 - The A750 (like most engine radiator cooled Auto Trans) does not have an internal thermostat so it relies on the engine thermostat for temperature stabilization for correct oil viscosity to operate and lubricate correctly. Did your Auto Trans Cooler kit come with an inline and returnable thermostat or did you place the cooler on the outlet side of the Auto Trans than the outlet to the Cooler goes through the normal radiator for temperature stabilization ?

[HK1837]

Will check, I put it where Wholesale Automatics told me to. Will be easy to check as the sender for the temperature gauge is on the fluid outlet to the cooler (bottom outlet from memory).

[rjstokes]

Thanks for the advice. I found an article reviewing the towing abilities of the car and the writer specifically asked Toyota why the tow capacities are different for the auto and manual. The response was :

“Having conducted robust global and local evaluation during the development of the Fortuner, Toyota engineers determined that these capacities were optimal for each transmission and will ensure long-term durability, as well as day-in, day-out reliability here in our Australian operating conditions.”

That being the case I think it would be prudent to leave it alone and rely on the 'robust evaluation'! For now at least.

Cheers!

[Gulfstream8]

Below is the research I did a number of years ago (updated for new 6 speed Tacoma) when I was thinking of installing a trans cooler - if it helps anyone make a call its all good if not crack a beer and laugh at me doing research

Toyota Tacoma USA factory tow packages

Tacoma V6 with A750E and A750F and current Tacoma V6 with 6 Speed auto (I was unable to find if this is the same new Auto in the current Hilux and Fortuner but I'm betting it is) ---- the tow packages include an external transmission cooler but most importantly they also include an external thermostat controller. (FYI the tow packages were to make the Tacoma compete with the competition at around 3,000kg - otherwise normal cooling was through the Engine radiator and the Gross Towing capacity was 2,273 KG). edit 13/Jul/2016- I forgot to add that the USA Tacoma "tow package" also gets an engine oil cooler as well (all this is $600US) but interestingly the Aussie V6 Hilux gets the Engine Oil cooler as standard ---- for people interested it sits under the oil filter and is a Water/Oil coil cooler.

If I was to install a transmission cooler I would import this or at least copy what Toyota USA have done and install a thermostat - or at the very least place the outlet of the aftermarket cooler to go through the standard Toyota engine radiator the way Toyota intended ---- presumably for Auto Transmission oil temp stabilization.

WS Transmission oil - which is used in these new Transmissions

The WS oil or World Standard oil has its viscosity set to the same standard as engine oil at an optimum of 100 degrees. Setting this standard makes it easier for engineering around the world to design for example an engine (or transmission)to run correctly. So let's say an engine is designed to have a core engine oil viscosity of 30 we should use an oil that ends in 30 like for example 5w 30. This will ensure everything works correctly like VVT and lubricants like oil sprayers under Pistons - the thicker the oil the less it will spray the way the engineers designed it. Same applies to we should never remove an engine thermostat as the engineers designed the engine and lubrication system to work accordingly at that temp. If we take Mobil 1 at 5w 30 for example it has a viscosity of 11 at 100 degrees centigrade and other brands are similar at this temp therefore setting a standard to build an engine. For the record Mobil 1 5w 30 has a safe operation temp of -40 to 200 degrees centigrade.

Sorry I had to use engine oil as an example as I could not find a spec sheet on the WS oil - but what this means is that WS oil has no problems running at 100 degrees C. The Tacoma service manual does indicate that the WS oil works similar to a good Synthetic oil where at lower temps it remains thinner than standard ATF. The WS also maintains Viscosity at higher temps. In other words its much more stable than normal ATF providing better gear changes and maintaining consistent clutch pressure at a wider temperature range.

I did however find operation temps in the Tacoma A750 service manual and it said the transmission performance will operate normally with sump oil Temperature of 20 to 110 degrees centigrade - above 110 and some problems described in the manual are "hard and erratic gear changes" and below 20 degrees "Slow Gear changes and possible clutch slip or Transmission shudder", I have experienced this parking the Lux up at Thredbo for a week in the snow and when I went to drive away it shuddered a little until the engine warmed up. The temp warning light on the dash however will not trigger until 150 degrees centigrade this would make sense as most spec sheets on normal Engine oil show a safe operating temp up to 160 degrees Celsius (unlike Mobil 1 at 200c) and FKM-Viton, Fluro Silicon, PPS, Torlon seals should be able to handle 150 degrees centigrade for hours on end - "But please note that at 150 degree temps it shortens the seals service life of the seals". Also the Auto Trans part of the ECU measures the Temp in 2 places for correct ECU calculation performance - one in the Auto Trans sump where the oil will be cooler and one in the torque converter where the oil is hotter but operational temp should be measured in the sump and not in the torque converter which will be hotter and is usually the outlet to the cooler or vehicle radiator.

Just my 2 cents worth and Im not an Auto Trans Expert nor do I have access to Toyota Australia's R&D or "Hidden Service Bulletins" its just why I would be careful installing after market coolers to these modern transmissions - especially if Toyota USA only sells their Tow Packages with a Thermostat included with the cooler. Maybe its just for fuel economy to get the Auto up to temp faster or it could be more important and that is holding the Auto Trans oil at a consistent temp where it can provide the correct operating pressures to hold clutch packs correctly etc to prevent slip and damage -- I honestly dont know. Maybe it is ok as HK1837 has documented above his Towing temp is now 75 which is well within the oil A750 oprational temp of 20-110 degrees centigrade. For me I feel that servicing the Auto with new WS oil and a new strainer is more important for extended life.

[rjstokes]

Thanks heaps for the detailed info. Interesting reading. Presumably you are involved in Globals or something similar with plenty of cruising time to ponder these things. I'm on the Boeing myself with slightly shorter legs but still long enough to read plenty! Thanks again...

Cheers!

[HK1837]

I just spoke to Rodney from Wholesale Automatics. Rodney is an auto trans guru. I asked about the above stuff and here are the answers.

For Canada, Alaska etc or similar Arctic environments you may need help with warming the trans fluid initially, BUT the torque converter will heat the fluid through shear action much faster than engine water will.

The ideal operating temperature for transmission fluid is room temperature (about 22degC) as this is the temperature that the seals in the transmission are cured at.

For the A750F they run the transmission fluid through the radiator first then through the air to fluid cooler. I explained to Rodney that in normal driving in city traffic (where the torque converter is working more) it rarely exceeds 60degC, he said that was perfect and that the air to fluid cooler is doing its job. His comment on Hilux autos is they have to have an external cooler especially carrying a load or towing, otherwise you are lessening the life of your auto transmission.

Note also that for the HD auto conversions that Wholesale Autos sell for Landcruiser utes and also for ZF boxes in Ranger, BT50 and Falcon they bypass the water altogether to avoid the ZF milkshake.

This is my comment - every auto tow vehicle I've ever had has had an external cooler, whether that be a factory accessory or my own design:

WB 1-tonner 3.3l manual, changed to a VK EFI trimatic (heavier duty 6cyl Trimatic than normal), no radiator in the circuit as it was a manual - used a big B&M cooler off a XF Falcon with tow pack and LPG copper fuel line for transmission fluid lines.

MQ Patrol ute, was a 4.0L manual but I converted to 302 SBC and TH400. Again no radiator in the circuit as I used the 4.0L Patrol one, just used a big B&M cooler again and LPG copper fluid lines.

HZ Holden 1-tonner 308 TH400 Overlander, had one of those alloy finned coolers in series with the engine radiator.

VZ Cross 8 - 4L65E 4spd auto with factory accessory 2500kg tow pack, used a small auxiliary cooler in series with the radiator.

Never had an auto problem in any of these. Seen plenty of Trimatic, 4L60, 4L60E and 4L65E transmissions fail from overheated fluid with people trying to tow with them with no auxiliary fluid cooler.

[Gulfstream8]

Ha ha nooooooooooo your making it hard for me HK1837 I did all that research over a Tranny Cooler years ago and made my mind up then I had an 1,800 Kg Flightcraft ski boat with a nice little LT1 Chev that I towed.

Rodney from what I understand is respected in the industry I trust people with experience in a field and it makes it very difficult to say ----- but I'm going to have to trust the Toyota Engineers on this one so maybe he will see my money anyway in a rebuild - I hope not as fair is fair I will owe you beer for me getting it worng

In addition to the reasons above why I'm not going to stray too far away from what Toyota Engineered.
Yes they do get it wrong sometimes!

The fliud check level procedure requires the A750 to be at 46 to 56 degrees c in the sump via a scan gauge (directly to the sump sensor not at the Converter) or the Toyota check light procedure and that's just at idle. But you start this procedure at less than 30c topping up the sump. Once you have topped it up you heat it up to 46 to 56c and let excess oil drain out of the sump. This alone as an engineer myself points to the fact that 60c is what Toyota Engineers intended the Transmission temp to be in service.

40 to 60 degrees seems to be what people in the USA are getting in normal driving and 80c working the torque convertor hard and it's what I have got here. Please note this is at the sump again.

Even the A750's in the Candain sold Tacomas (which are equiped with a transmission heater via engine heat not torque convertor) return similar temps - modern convertors simply do not generate enough heat anymore like old TroubleMatics or Turbo 400's as they are programmed to lock up ASAP all the time; unlike a Turbo 400 which does not have a lock up convetor and is one of the reasons it generates so much heat plus compared to modern autos it wasted a lot of energy just to run it.

The hottest my A750 has gotten is almost 90 degrees - and that was not towing it was around town when the torque converter was actually working most and it was one of Sydney's hottest days with my cranky wife yelling at me because we were late ------ we were late because I was playing with a mates Scan Gauge I borrowed

80 Degrees Centigrade is normal for an engine and engine seals. The 1GR-FE V6 Thermostat is not fully open until I think 84 Degrees so it's not like the Seal Tech or Oil Tech is not available for the Transmissions.

So given the above that internal sump temperatures unloaded and loaded are the similar I would have to conclude the temp range above is what the Toyota Engineers intended and as I cannot disprove it Like Dyno testing a standard Toyota Air Box V's a TRD CAI I'm going to have to trust the Toyota Engineers on this.

I would though however respectfully disagree and I absolutely mean no offence about your experience with older transmissions, don't worry I have had my problems with them too - Modern Transmissions are light years ahead of the Turbo 400 which was first sold in the 1960's, both in terms of seals and how they operate.

The Turbo 400 had no lock up convertor and was put into vehicles by companies that did the least they had to do to sell vehicles and the coolers were never big enough. With no lock up convertor (and in my case) towing a boat it would get stinking hot because as you know the convertor would be slipping - no lock up. Couple this together with 1960's seal technology ----- remember Chev and Holden were still using rope seals YES rope seals around the crank and sump in the 1970,s ------ and low temp ATF (Auto Trans Fluid) plus old technology clutch material also would fall to bits with any high temps and there would be problem after problem if not kept cool.

Towing with an A750 - and possibly most modern Transmissions

I remember a member on here Hilux Maxx posting up a warning about towing with these years ago and he was 100% right. He basically said people when towing with one of these or any Auto forget the basic principles of towing. If you were in a 5 speed manual you would never labour the engine in 5th or the overdrive up a steep hill as it can damage the gear box and possibly the engine. He suggested pulling it down to 4th for steep hills because the Toyota ECU has its own mind made up and will always push to 5th for economy.

When I looked into this I found out other things - the A750 could be excused as a 6 Speed Auto. You may have noticed that it will uncouple its lock up convertor on the Hi-way in 5th to give you an artificial extra gear rather then changing down a gear. Now this is great and all but when your towing if the A750 stays in this unlocked mode that's when I see high towing temps.

So I can highly recommend Hiluxmaxx advice when towing heavy with the A750 chose wisely that 5th gear. That's what I have always done and never had a high temp in the Auto.

The last thing that may interest you as I know you have the 1GR-FE is that the TRD CAI that I installed that reduces the load that the ECU sees has also helped with Auto Temps as the Auto does not unlock as frequently or hunt gears (not that it was that bad anyway).

Anyway like I said I will have to trust the Toyota Engineers on this as I believe installing a cooler without a Thermostat to control temperature is not how it was designed by people much smarter than me. So lets agree to disagree.

Cheers

[HK1837]

My temperature gauge is installed on the "hot" outlet of the box, this is the oil leaving the gearbox workings I think before going through the cooler(s) and then returning to the sump. At this point the oil without an auxiliary cooler easily exceeds 100deg C in summer with simple no loaded driving.

The best thing you can do for auto trans fluid is keep it as cool as possible, not cold but cool.

My take on Automotive Engineers - they are no different to any other Engineer. I'm an Electrical Engineer. I always design with overkill. However Engineering Managers are nearly always Accountants in Engineer's garb and will always make you design for a "just fits" design, with no Engineered "fat" in the equation. In the auto industry everything is cut to the bone and as cheap as possible as the business is run by Accountants to make as much money as possible. If they can save 6c per car by using 3 less bolts they'll do it. The cooling ability of the transmission is no different to any other part of the car. Why do we all change suspension, shocks, tyres, brakes etc? Because the factory stuff is cr@p and only good enough to do a basic job and get through the warranty period. The same A750F in a 100 series has massive air to fluid transmission cooler. Why? Because it is heavier and can tow more. So when we load up out Hiluxes and tow with them wouldn't the A750F only be helped by additional transmission cooling?

My take on it, just like it is with most any other thing is overkill is better. It is the same reason I use 10W-40 oil. Owner's manual says if towing or operating at extreme (hot) conditions use 40 grade oil, or even 50. 30W is recommended only for ambient temperatures below about 34degC. Same reason I have bigger brakes now.

I'd trust Rodney over manufacturer's any day! These guys can make a known weak transmission like a 4L60E bulletproof. Why couldn't GM Powertrain Engineers do that? Because they are driven by cost far more than reliability or longevity. What is the secret to making any of those factory transmissions last longer in addition to better componentry? Keeping them cooler. BIG COOLERS!

I'll definitely be looking into the TRD CAI. I've noticed how well my SR5 goes on days when it is like 5-6degC ambient, until everything heats up then it is the same.

[Gulfstream8]

It's all good mate and I respect your view. When it comes to aftermarket parts we should all do research and come to our own conclusions as some can be expensive, dangerous or don't work.

As you can maybe tell I don't tend to sway too far past manufactures recommendations or factory parts with TRD Shocks, TRD CAI and 2009-2011 Tacoma Headers and FJ Cruiser wheels etc on my Lux. I believe Toyota and it's engineers get it right more often than other maufauctures and the day I jumped out of Holden V8 into my first Toyota (Supra) was a great day. God I miss that car

All the best

Cheers

[HK1837]

Send me a PM with your email address and i'll send you my dyno curves. Would be cool to overlay them or at least compare. I'll do another run with the CAI when I fit one.

[Gulfstream8]

Send me a PM with your email address and i'll send you my dyno curves. Would be cool to overlay them or at least compare. I'll do another run with the CAI when I fit one.

Sure I'm more than happy to help - but it's not ideal comparing Dynos to other Dynos. Usually you compare the gains made in a percentage if it's not possible to place the same vehicle on the same Dyno.

[Gulfstream8]

Thanks heaps for the detailed info. Interesting reading. Presumably you are involved in Globals or something similar with plenty of cruising time to ponder these things. I'm on the Boeing myself with slightly shorter legs but still long enough to read plenty! Thanks again...

Cheers!

"If it's not Boeing I'm not Going!!!"

Sorry rjstokes I almost forgot this was your first post after I got carried away Yes I use to swing spanners on planes but like the rest of us we become infected with that need to "we must find out the answer no matter what". So yes I tend to research a little too much, well mechanical anyway.

Mate I would love to hear your thoughts on the Fortuner - the Mrs has got her heart set on the CX5 but I would love the Fortuner.

[HK1837]

Send me a PM with your email address and i'll send you my dyno curves. Would be cool to overlay them or at least compare. I'll do another run with the CAI when I fit one.

Sure I'm more than happy to help - but it's not ideal comparing Dynos to other Dynos. Usually you compare the gains made in a percentage if it's not possible to place the same vehicle on the same Dyno.

Agree, but mine was run on the dyno as a standard vehicle and then run on the same dyno with the Beaudesert Exhausts and XEDE processor with two maps. I have dyno runs also for both XEDE maps running E10 and then 98. So will be good comparisons for % gains and also the % gain at specified rpm against other stuff. I'd put them up on this site but it doesn't accept pictures.

[Gulfstream8]

Send me a PM with your email address and i'll send you my dyno curves. Would be cool to overlay them or at least compare. I'll do another run with the CAI when I fit one.

Sure I'm more than happy to help - but it's not ideal comparing Dynos to other Dynos. Usually you compare the gains made in a percentage if it's not possible to place the same vehicle on the same Dyno.

Agree, but mine was run on the dyno as a standard vehicle and then run on the same dyno with the Beaudesert Exhausts and XEDE processor with two maps. I have dyno runs also for both XEDE maps running E10 and then 98. So will be good comparisons for % gains and also the % gain at specified rpm against other stuff. I'd put them up on this site but it doesn't accept pictures.

You will need to create a "Photo Bucket" account then copy and past the link of the photo into the thread your writting.

There is a how to somewhere here on New Hilux but I'm sure you will be able to work it out. Just be a little carful using Photo Bucket as I'm unsure about its security.

FYI - dont post it here as the moderators dont like us getting too far off topic

Cheers