Automatic Transmission Temperatures on a Mazda BT-50 / Ford Ranger


G’day guys and girls.

In this post we will be discussing how to lower automatic transmission temperatures, the principles and methods can apply to any car, but the products discusses will be for the Mazda BT-50 and Ford Ranger (from when they shared a design).

I will give a brief rundown on why you would want to lower your transmission temperatures and will be discussing it from the point of view of those who have a 6R80 transmission, built by Ford.

We will discuss why you would want to lower your automatic transmission temperatures, the three options readily available to you as an owner and the pros and cons of each.

At the end I will explain why I chose the method that I did as well as the results I have seen in lowering my automatic transmission temperatures through early testing.

So, how to lower your automatic transmission temperatures? Here’s the 3 main options available (affiliate links):

Just before we get into how to lower your automatic transmission temperatures we’ll discuss why we need to.



Why I wanted to know how to lower automatic transmission temperatures


I don’t tow, but the car I purchased did have a bull bar and a tow ball. This gives me the impression that maybe it was used to tow a caravan, as there were no liveability mods done on the car itself.

For me it all came down to wanting a clean slate with my transmission. I knew that the Ford Rangers and Mazda BT-50s transmission had reports of failure and I wanted to get on the front foot and avoid this. Preventative rather than reactive maintenance.

So as part of my 4WD build I made sure that this was one of the first things I did, along with installing an Ultragauge to monitor the temperatures before and after the install to ensure I got my moneys worth!

So that’s how I started looking at how to lower automatic transmission temperatures. All I want is reliability and perhaps comfort, reliability is key. If I spend thousands on a car then I want it to last, that’s basically what this was for me.

Transmission Oil Cooler Install Video


If you’d rather watch a video, this is not only an install video but also explains how to lower automatic transmission temperatures in video form using the three methods we will discuss in this post.


*Affiliates Disclosure

Affiliate links are present on this page. Through partnerships with, but not limited to: Amazon, eBay and Commission Factory, I will make a small commission through qualifying purchases. This comes at no extra cost to you and is just a way for me to try and support myself and the blog.  Thank you.

6R80 Transmission


I want to briefly explain the workings of the 6R80 transmission so we get an idea of who needs to lower their automatic transmission temperatures and why.

The 6R80 transmission is a 6 speed automatic transmission from Ford that is used in all sorts of cars, not just the Mazda BT-50 and the Ford Ranger, but also cars like the Ford Territory and F-150 “trucks”.

So it has a massive amount of field experience, with Ford having built it well enough, but not perfect by any means.

This post is not meant to scare anyone into thinking these transmissions are poor, they’re not. They have had reported issues though in certain conditions and that is why we want to know how to lower automatic transmission temperatures, to deal with those specific conditions.

The sheer amount of them on the road means that it’s inevitable for some issues to arise.

Where does it go wrong?


Where the transmission struggles is that as people load up their vehicles to go heavier and heavier, often exceeding GVM and/or towing right at the limit of GCM, the gearbox can fail in a number of ways.


Overheated transmission oil

The transmission oil is meant to operate at about 85-95°C (more on this in a bit). When temperatures exceed that then damage can occur to the internal components, solenoids, rubber seals etc.

It also degrades the oil, it might seem like a small difference from 95 degrees to 103 degrees but it doesn’t take much.

Given the sometimes ridiculous temperatures in Australia in the places that people like to tour, these temperatures can exceed 102-105°C without even towing anything.

When people are towing, the temperatures will approach or exceed 110°C.


Blocked thermal valve

Transmission oil operates at its best at a certain temperature, this is what this valve is for, to stop it from being cooled unit it reaches that temperature.

As people tow heavier and heavier loads, the transmission oil temperature rises and damages internal components, the parts then can introduce contaminents into the oil flow which can block the thermal valve.

This valve is what gets the temperature of the oil to the ideal range of 85-95°C. It stops the oil from going through the cooling system (a heat exchanger) until it reaches this temperature.

If this valve becomes blocked then the oil will not flow through the oil cooler at all, regardless of if the transmission has reached the ideal temperature or not.

This will cause the car to alarm and go into limp mode.


Coolant contamination

The 6R80 transmission does not have an oil cooler, optioning for a heat exhange unit instead.

What this does is use coolant, which is cooled by the radiator, to flow next to the transmission oil (once the valve opens) and transfer the heat.

An issue that had been reported is the breakdown of the dividing walls which allows coolant to enter the transmission and contaminate the oil, adding water to the mix and ruining the lubrication.

How to Lower Automatic Transmission Temperatures in the Mazda BT-50 / Ford Ranger


So we can see that the 6R80 has some potential shortcomings.

I would urge most people to take all of the above with a grain of salt, because the people who tell you these things are also those who wish to sell you stuff.

That isn’t to say they’re lying, just that these issues happen to a select bunch of people and are not going to affect every Mazda BT-50 or Ford Ranger using that transmission.

If you tow, or are approaching GVM, or run really large tyres, or tour in extremely hot environments, then you really need to look into how to lower automatic transmission temperatures, which I guess is why you’re reading this.

As briefly touched on in the intro there are 3 main options to lower your automatic transmission temperatures which we will go through here.

You can combine any of these 3 options, you can go for all 3 if you wish, but I think that it is mostly a waste of money going for any more than 2 of these options.

*Affiliates Disclosure

Affiliate links are present on this page. Through partnerships with, but not limited to: Amazon, eBay and Commission Factory, I will make a small commission through qualifying purchases. This comes at no extra cost to you and is just a way for me to try and support myself and the blog.  Thank you.

Option 1 – Transmission oil cooler kit


Check out the latest kit here (eBay).

The transmission oil cooler kit is the first thing that people think of when looking into how to lower automatic transmission temperatures. This is what I installed, my reasoning will be further down the post.

When you buy this kit, it comes with:

  • Oil cooler.
  • Hoses.
  • Mounting brackets.
  • Spacer (needed for some vehicles).
  • Hose clamps.

Outside of that, you will need to supply cable ties and there’s an option to add 1 litre of transmission fluid to the purchase for topping up the oil afterwards.

I personally recommend doing a complete flush of the transmission oil (draining it, not flushing the torque converter etc) after fitting an oil cooler so that you have a clean slate at the point the modification was made.

No point protecting bad oil, so I’d recommend not worrying about the 1L oil top up bottle and just having 6-9L worth of oil to do a full oil pan drain and refill after the oil cooler gets installed.



  • This kit will remove the heat exchanger from your cooling system, because this transmission oil cooler will take its place. This eliminates the heat exchanger as a point of failure.
  • This oil cooler is much better at cooling the oil down, way better than the heat exchanger.
  • Because the valve has not been removed, the transmission oil is still getting to its ideal temperature before being cooled which is good for shifting performance.



  • As the thermal valve is still in the system there is the slight chance that it may get blocked one day rendering the oil cooler useless.
  • Potential that it will clash with any aftermarket intercoolers that you might want to fit (not saying it will but there’s that possibility).
  • Patially blocks the intercooler, although I haven’t noticed any changes to how the car runs.
  • Won’t have any affect until the thermal valve opens, which might be too late if you’re towing massive loads (but I can’t say whether that is the case or not).


Who’s it for?

The transmission oil cooler can be used by anyone, I assume people will want it regardless of if they choose one of the following options on top of choosing this option.

It massively outperforms the heat exchanger and I installed it despite not towing, just to keep those temperatures at the absolute peak temperature and not let them go higher in summertime.

I think this is not just for those who tow, but those who put the engine through hard work semi regularly. At the end of the day it is a reliability modification and they’re my favourite types of modifications.

Option 2 – Constant Flow Thermal Valve


Check out the valve here (eBay).

The thermal bypass valve with constant flow is the second thing that people think of when looking into how to lower automatic transmission temperatures.

The way this works is that remains open all of the time, so it can not become faulty and ever get stuck closed.

The main benefit of this install though is that whether you stick with the heat exchanger or not, the transmission oil is being cooled straight away, as soon as you turn the key.

I actually purchased this valve in a service kit, but I did not install it which will be explained later on.



  • Cheapest of all the modifications you can do, so long as you install it yourself.
  • Cooling takes place immediately, and never stops until the car is switched off.
  • Eliminates the factory thermal bypass valve as a point of failure from the cooling system.



  • Transmission oil temperature is not being bought up to its ideal operating temperature.
  • Without pairing this with an oil cooler kit then you still have the heat exchanger as a possible failure point.
  • Heat exchanger may not provide adequate cooling over a long drive, despite the head start given to it by cooling instantly it might not be enough.


Who’s it for?

This valve is for people who are towing heavy loads.

I might not recommend this for those who live in Tasmania for example, but those touring the mainland I don’t think the cold starts will be too big of an issue.

If you’re towing and touring up north in the heat, this valve would be a great choice to keep the transmission in its prime, but I would still recommend that it was paired with option 1 for optimal performance.

If anyone has any experience using this valve in cold temperatures where the transmission oil no longer gets up to temperature then I would love to hear how/if you notice any differences.

Option 3 – Extra Capacity Transmission Oil Pan



This extra capacity transmission oil pan offers 3 litres of extra transmission oil, as well as including a handy drain hole for easier transmission oil servicing.

I must admit, the drain plug is a big bonus, but if you have your cooling sorted then you shouldn’t have to drain this very often.

The pan is made from aluminium, so it allegedly dissipates heat quicker, is stronger (but you should have bash plates) and the fins along the bottom aid cooling even more so.



  • Extra 3 litres capacity allows better cooling as there is more to circulate.
  • Drain plug on the bottom for much easier servicing in the future.
  • Extra 25% oil means more longevity from the oil (like a 5-way tyre rotation instead of a 4-way rotation).
  • Better cooling design due to aluminium housing and cooling fins.
  • Mechanically stronger than the factory pan.



  • If you don’t pair this with an oil cooler kit then the heat exchanger remains as a point of failure.
  • If you don’t pair this with the valve then the factory valve remains as a point of failure.
  • Might be a bit excessive to take this step if you have already chosen one of the first two options.


Who’s it for?

Extremely heavy towing, people who want all 3 options or perhaps those who don’t run a transmission bash plate and would like the extra strength?

Although it’s not going to take hits like a bash plate, it will provide more ground clearance than a bash plate, but I’d not recommend forsaking a transmission bash plate.

This is a fine option for those who still want to get their oil temperatures up to the ideal operating temperature but don’t want to fit an oil cooler that will be covering the radiator and intercooler up the front.

My Choices


So there are the three options, now I will discuss what I thought was the best combination when researching how to lower automatic transmission temperatures.

*Affiliates Disclosure

Affiliate links are present on this page. Through partnerships with, but not limited to: Amazon, eBay and Commission Factory, I will make a small commission through qualifying purchases. This comes at no extra cost to you and is just a way for me to try and support myself and the blog.  Thank you.

Why I installed a transmission oil cooler kit


As someone who had been monitoring their automatic transmission temperatures with an Ultragauge MX 1.4 (eBay) I knew that my temps were rising to 95-98°C here in the winter, albeit on long drives only.

In the summertime they had regularly been spotted at 100°C, the highest I had seen was 103°C from memory.

I decided to get the transmission oil cooler kit because I still wanted my temperatures to be at the best conditions for the oil and the shifting, but I wanted it to stop there.

Nobody was able to tell me accurately what temperature the factory valve would open, by installing the cooler I would be able to figure it out exactly with the Ultragauge.

The other benefit was of course removing the heat exchanger from the car which removes a point of failure.

This would also allow me to drain the oil and start afresh with the new cooler, knowing that from that point onwards the temperatures would be controlled and the oil should not need looking at for 100,000 kms or so.

Why I ordered the bypass valve but didn’t fit it


As stated above, I planned on doing a transmission drain and refill. The bypass valve can be purchased by itself, but also in kits. Since I was looking for a gasket and filter already, it made sense to just chuck on the valve by purchasing this kit here (eBay).

What this would allow me to do is monitor the temperatures with my transmission oil cooler operating, then if for some reason it was not keeping the temperature cool enough I would have the valve in the garage waiting to go.

If I do later find that I want to fit the valve, that means draining the oil again which means that it is effectively a newer mix getting added even more so than with just the one drain and refill.


Why I am not worried about the factory valve sticking

As someone who purchased a car with low kilometres (35k) and who has installed an oil cooler on at an early stage, I don’t think it is likely that my transmission has deterioration to the point that the valve will stick.

As I do the drain and refill, I will be changing out the filter as well as 60-70% of the oil for brand new oil, I will be able to check the magnet inside the transmission pan for signs of metal shavings.

On top of this, using the Ultragauge I have set a high alarm, so if my automatic transmission temperature goes over ~103°C (if forget exactly what temp I set it at), then the alarm will go off.

This alarm will alert me long before the car would send off an alarm, which is rumoured to be about 130°C, far too late if you ask me. This way I can nurse the car to safety and fit my bypass valve that is waiting in the garage at home.

Does the transmission oil cooler work?


It does, very well in fact.

After testing the car out trying to get it up to the previous temperatures, it would not budge past 85-86°C. The only time it climbed above that was as the car slowed for red lights as there was then no air flow over the cooler.

This tells me that the factory valve opens at 84°C in my vehicle, each valve might vary slightly but should be within a few degrees celcius of that.

This is in the winter mind you, but even in the summer, I can’t see it approaching that 96°C threshold that makes me nervous. If it consistently goes above that then I will add the valve to the mix.

At the moment, I see it as having the best of both worlds, I have the oil at the ideal temperature for shifting, but I also don’t have it going any higher than that.

At the time of testing the car was running 265/65/R17, it weighed 2400kg and the ambient temperature was 18°C. I took it through the hills and along freeways at 100 km/h for over 45 minutes and couldn’t get it to budge higher.

How to lower automatic transmission temperatures: summary


Ok that is it guys, hopefully that gives you some food for thought. Now you know how to lower automatic transmission temperatures and can begin the purchasing or continue researching.

Thos are the 3 options that I found when researching how to lower automatic transmission temperatures but if you know of any others then feel free to leave a comment.

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