I notice a few members recommending or installing additional transmission coolers.
I'm just struggling to understand if thats necessary on the AWD 5 speeds?
I can see the logic if towing or racing, but not for normal street driving?

(By street driving I mean no towing, and just regular suburban/city driving within the speed limits).

The only tangible benefit I've been able to identify so far for normal street driving is longer ATF life; but if I'm replacing the ATF more frequently then is that applicable?

Can anyone explain what the key benefits are and why extra cooling is worthwhile?

peace of mind.....heat is the killer of these boxes

Not just recommended, but considered essential especially on the 5 speed.

I installed a transmission cooler on mine with a bypass valve that as the name suggests bypasses the cooler if the fluid isn't too hot.
After installation I would often touch the cooler to see if and when the ATF gets too hot.
To my surprise it really does not take much at all for it to exceed the ideal temperature.

My best advice is to install it on the passenger side as that is where the A/C fan switches on + the first fan that goes on when the engine temps rise

Not just recommended, but considered essential especially on the 5 speed.
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After installation I would often touch the cooler to see if and when the ATF gets too hot.
To my surprise it really does not take much at all for it to exceed the ideal temperature.
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If I understand, you mean that you have a thermostat set to open at a certain temp?
Couple more questions then; what is the ideal operating temp and how do we know that?
Second, how far above the optimal temp is the thermostat set so it doesn't open too early?

Yes you understood correct.

My understanding is that it is never really completely closed, but is full open at 87 degrees or so which is ideal.
The thermostat is specifically designed for this purpose.
Your ATF fluid is likely hotter than ideal most of the time I would say

Yes you understood correct.

My understanding is that it is never really completely closed, but is full open at 87 degrees or so which is ideal.
The thermostat is specifically designed for this purpose.
Your ATF fluid is likely hotter than ideal most of the time I would say
Well if its the type that doesn't fully close then it will always feel warm to the touch due to the flow of ATF through it, so I dont see how that says anything about your ATF being too hot at any given moment.

I'd also like to know what the operating temp and what the min and max temps should be, if anyone has that info.

I'm pretty convinced about the value of an additional cooler thats regulated by a thermostat having a benefit *IF* the ATF exceeds max temp; but I still havent heard any evidence that these transmissions typically overheat under normal conditions?

Even though it doesn't fully close, when the ATF is not too hot the flow is minimal.
There are times that I touch the cooler and it is warm on the inflow side and cool on the outflow side. Obviously this is a minimal flow time.

Most of the time (especially now in warmer months) the cooler is too hot to touch, and this is on the outflow side.

In the end, your transmission will run fine at 10 degrees hotter than ideal, but the longevity is already suffering.
I read somewhere once (not sure how credible this is) but if your transmission is 11 degrees hotter than ideal through it's whole life, it will essentially halve the life expectancy.

The only tangible benefit I've been able to identify so far for normal street driving is longer ATF life.
No, that isn't the benefit; the benefit is longer transmission life. I certainly wouldn't recommend extending ATF changes just because a cooler is installed.

My understanding is that it is never really completely closed, but is full open at 87 degrees or so which is ideal.

Even though it doesn't fully close, when the ATF is not too hot the flow is minimal.
If you used the kind of bypass thermostat I use (which is what we discussed off-line), I does fully close when the ATF is below optimum temperature. In that state, the bypass thermostat simply returns the ATF to the transmission.

IMHO, these setups are not required for the kind of use KWAWD describes (towing, and just regular suburban/city driving within the speed limits) but, at all of $100-150 fully installed (DIY ain't exactly hard), it's cheap long-term insurance.

Macropod, yes I am talking about the same bypass valve you have. I read somewhere that it never fully closes though not sure how accurate that is.

The thermostat was $50 delivered.
My opinion is that it's better to have a thermostat and larger than necessary ATF cooler.

No, that isn't the benefit; the benefit is longer transmission life. I certainly wouldn't recommend extending ATF changes just because a cooler is installed.
So does that mean that transmissions are failing earlier than they should and, if so, why dont i see many posts along the lines of "another dead tranny", or "my tranny just died", etc ?
I see posts here about wave spring failures and subsequent damage, but otherwise not much about failed transmissions? No more than any other car?
In the list of common faults i dont see "overheating transmissions"?


IMHO, these setups are not required for the kind of use KWAWD describes (towing, and just regular suburban/city driving within the speed limits) but, at all of $100-150 fully installed (DIY ain't exactly hard), it's cheap long-term insurance.
If nothings broken then why pay $ to fix it? Actually it introduces risks IMO.

So does that mean that transmissions are failing earlier than they should and, if so, why dont i see many posts along the lines of "another dead tranny", or "my tranny just died", etc ?
The only time you're likely to see clear evidence of a shortened life is when the car has been used for towing without one. IIRC, there have been posts here about exactly that happening.

If nothings broken then why pay $ to fix it? Actually it introduces risks IMO.
You're entitled to that opinion, of course, but it's not one I share.

Guys, if theres no objective evidence of these transmissions usually overheating and the current arguments are based on intuition about AWD's being "harder" on the transmission than FWD's then its pretty difficult to accept that an additional cooler is warranted.

I would like to install a temperature guage somewhere so that I could monitor the ATF under different conditions. But I'd also need to know what the normal operating temp is as well as what the maximum temp is. I note that unlike engine oil the original engineers didnt think a guage was even necessary, which seems to be typical for ATF, so it must be a low rsk issue.

I think replacing the wave spring makes a lot more sense to me right now.

I remember Mal mentioning that he has installed a temp gauge to a 3rd gen and the ATF temps spiked especially in traffic.

As for the ideal temp, I believe it is close to engine oil. You can do a search on google for ideal oil temps.

I urge anyone with a 5 speed (FWD or AWD) to do a preemptive wave spring replacement. I have (as did someone else I know) and both our wave springs came out in pieces.

the current arguments are based on intuition about AWD's being "harder" on the transmission than FWD's
From what I can see, you're the first to suggest any such argument - in this thread, at least.

I note that unlike engine oil the original engineers didnt think a guage was even necessary
The oil gauges were pressure gauges, not temperature gauges. You generally won't find an oil pressure gauge on any modern vehicle - or even a water temperature gauge on some current models.

... which seems to be typical for ATF, so it must be a low rsk issue.
For the kind of driving you've described, certainly. Just don't try towing a boat or van without one.

I think replacing the wave spring makes a lot more sense to me right now.
For L models & earlier, you may well be right. I've not seen any reports of wave spring issues with W models.

I remember Mal mentioning that he has installed a temp gauge to a 3rd gen and the ATF temps spiked especially in traffic.Thats interesting, is there a thread anywhere here on his findingd?


I urge anyone with a 5 speed (FWD or AWD) to do a preemptive wave spring replacement. I have (as did someone else I know) and both our wave springs came out in pieces.Yes, I'm currently thinking along those lines. Too many reports here of spring related issues to ignore.

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For the kind of driving you've described, certainly. Just don't try towing a boat or van without one.

Yes, I think thats a different scenario and I can see the logic in that. Towing must put a dramatic load on the system, far beyond "normal" operation.

The AWD is heavier and has higher driveline losses, I believe it's logical to assume it is harsher on the transmision/ATF but may be a relatively negligible amount.

As for where Mal mentioned it, it would be in one of the many, many ATF cooler threads on the forums.

For an indication of the effects of heat on auto transmission life, see: http://myautomatictransmission.com/temperature-chart.htm

The AWD is heavier and has higher driveline losses, I believe it's logical to assume it is harsher on the transmision/ATF but may be a relatively negligible amount.
A "relatively negligible amount" sounds like almost nothing to me...

For an indication of the effects of heat on auto transmission life, see: http://myautomatictransmission.com/temperature-chart.htm
.
That site states that overheating causes oxidisation of the ATF which in turn results in inefficient lubrication. They say that:

approximately 90% of all automatic transmission failures are due to fluid (ATF) breakdown caused by excessive heat.
I think this is why we should ensure the ATF is regularly replaced and before its too oxidised. I'm currently monitoring the ATF monthly and replacing at 20,000 k's instead of 45,000. Overkill? Maybe, but small price compared to a damaged transmission.
I've made myself familiar with how the ATF looks when new and watching for the signs of dirtiness due to oxidisation.

I am lead to believe that the AWD transmission is in effect the same as the FWD for the most part.
The ratios are identical

Ive had my ralliart for a few months now. I had changed oil etc and decided to put it in last week for a transmission service. The car has been driving fine but just wanted to get it done for piece of mind. I asked the transmission guy what he thought about replacing the wave spring while he had it. I had already bought a spring just in case. Anyway he said unless I was going to tow something or go on a long drive to qld then he wouldn't worry about it for now and hope I never need to use the wave spring. Guess what. When he pulled things apart, just like many other people, he found a piece of the wave spring. Needless to say sometime later and many dollars later the new spring was fitted and transmission serviced. He wants it back in 1000 ks to check on things and wll be putting in an additional cooler.

I've got a large inline cooler fitted on the passenger side of mine. The reason being, greater transmission life by keeping trans temperatures in check. I also run an external trans filter & flush every 25,000 kms with genuine Mitsubishi transmission fluid. AWD INVECSII trannys are expensive to rebuild & no guarantee that a second hand swap will be much better.
I've also had the wavespring washer replaced a few years back with the better unit after the tranny specialist found bits of it stuck to the magnetic oil drain plug.

For the sake of say $150 (DIY) this is the best insurance you can get for your car. Heat is an automatic transmission killer and as we all know the Magna autoboxes are not a strong point. Whilst you fit the cooler you can flush the transmission at the same time for piece of mind. Go one step further and put an in line filter in like a magnefine.

For the sake of say $150 (DIY) this is the best insurance you can get for your car. Heat is an automatic transmission killer and as we all know the Magna autoboxes are not a strong point. Whilst you fit the cooler you can flush the transmission at the same time for piece of mind. Go one step further and put an in line filter in like a magnefine.
I'm not convinced. I think monitoring the ATF regularly and replacing it when it's starting to become oxidised is the answer. I'm currently using a baseline of 20k change but would do it even earlier if it started to look too dark.
As far as the Magna transmissions go, I believe they're extremely reliable when maintained. The only issue is the wave spring.

I'm not convinced. ... I'm currently using a baseline of 20k change.
Considering MMAL's recommended 45000km ATF change frequency on an AWD, guess how many km you'll have done before you've thrown away more $ than a cooler would cost by unnecessarily frequent ATF changes instead of installing a cooler and keeping to the recommended change frequency?

Considering MMAL's recommended 45000km ATF change frequency on an AWD, guess how many km you'll have done before you've thrown away more $ than a cooler would cost by unnecessarily frequent ATF changes instead of installing a cooler and keeping to the recommended change frequency?
My choice of the 20k figure is an arbitrary starting point and is yet to be tested. It may turn out to be much better than that, (although nowhere near 45 I'm sure).

An additional cooler *may* reduce the rate of oxidisation but I dont believe that it would be enough to support the 45k interval.
Lets just for aguments sake say the additional cooler provides a 20% benefit, which I suspect is way too generous, but just for argument lets go with that.
Lets also for the sake of the argument assume my 20k baseline figure turns out to be correct, (without an additional cooler).
That means the additional cooler results in service intervals at 24k instead of 20.
Weigh that up against installing and maintaining the cooler, (which btw is adding complexity to the system).

What I'm saying is lets simply monitor the ATF and detect when it needs changing and then, at that point, change it - whether thats 20,25,30 or whatever interval, rather than waiting for some pre-determined date to change it (with or without a cooler).
After a couple of cycles I should be able to say what the typical service interval for my car is.

Lets just for aguments sake say the additional cooler provides a 20% benefit, which I suspect is way too generous, but just for argument lets go with that.
Lets also for the sake of the argument assume my 20k baseline figure turns out to be correct, (without an additional cooler).
I see no basis for either assumption, especially the 20% for the cooler you say you're not going to install... What makes you think that, with a cooler installed, the ATF isn't good for 60000km or more, all due to the lower operating temperature (not that I'm proposing to extend the ATF change frequency)? After all, FWD Magna autos have an MMAL-recommended ATF change frequency of 105000km.

ATF change frequency is 45,000km according to the service manual.
From what I have read though that is way too much, and should be changed around 20,000km.
With an ATF cooler supposedly closer to 45,000 is possible though personally I would not go that much.

Keeping in mind that the damage to the transmission is not done only when the ATF is too hot. Once the ATF overheats it loses its qualities and no longer protects the transmission as it should.

I've read a technical report suggesting that ATF fluid at 11 degrees C hotter than ideal will halve the life of a transmission.

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I've read a technical report suggesting that ATF fluid at 11 degrees C hotter than ideal will halve the life of a transmission.
This is the other thing I want to do; monitor the ATF temp. But I havent been able to find out what our "ideal" temp is.
I'm open to the idea that if the ATF is running consistently above optimal temp then that may reduce its effectiveness, but cant find any info on the min/max/optimal temps for our cars or the ATF.

This is the other thing I want to do; monitor the ATF temp. But I havent been able to find out what our "ideal" temp is.
I posted a link discussing just that earlier in this thread...

ATF change frequency is 45,000km according to the service manual.
From what I have read though that is way too much, and should be changed around 20,000km.
Yes, you'll read a lot of uninformed opinions and anecdotes to that effect but, when it comes to research published in any recognised journal, you'll be hard pressed to find anything relevant. I'm far more inclined to rely on MMAL's (conservative) recommendations, which one can be assured of being based on their own testing, than anyone else's unsubstantiated claims.

I posted a link discussing just that earlier in this thread...
That links to some generalised info with tables showing temperature ranges and mileage. Nothing specific to our transmissions and they dont provide any source for what they're saying anyway.

I expect our transmissions have a minimum operating temp to ensure correct operation of the ATF as well as an optimum temp and a maximum temp. I assume that those parameters might vary from car to car, ATF to ATF...
Cant find anything on that so far.

That links to some generalised info with tables showing temperature ranges and mileage. Nothing specific to our transmissions and they dont provide any source for what they're saying anyway.
You're extremely unlikely to find anything specifically for a Mistusbishi Magna/Verada AWD transmission. That said, ATF in general reacts in fairly consistent ways to heat, and that's what the link I posted deals with. A few degrees one way or the other in what a given ATF's optimum temperatures are isn't going to make a huge difference when you start dealing with temperatures tens of degrees and more over the optimum. As noted on that site, who's advice appears to come from the Automatic Transmission Rebuilders Association, "The general rule of thumb is that for each 20 to 25 degree increase in temperature the transmission's life expectancy is cut in half" (note that temperatures there are in Fahrenheit, not Celsius). If you want more definitive reference 'sources', you're welcome to do your own searching.

In regards to the MMAL service schedule, a big part of selling new cars is ongoing ownership costs such as servicing, so I think it's not unreasonable to suggest that MMAL may have embellished the service intervals. The engine oil was at 15,000km intervals and at the time they were likely using mineral oil, which seems overly optimistic.
With fully synthetic oil that wouldn't be an issue of course, but I didn't read anywhere in the manual that only fully synthetic oil is to be used.

KWAWD, the ideal temperature is about 87 degrees, with 80-90 being very good.

KWAWD, You are correct, for the reasons you gave in the OP, you don't NEED to add an additional transmission cooler. For the very same reasons you also gave, is why I have added an additional transmission cooler. Cheers, Bill.

I'm not convinced. I think monitoring the ATF regularly and replacing it when it's starting to become oxidised is the answer. I'm currently using a baseline of 20k change but would do it even earlier if it started to look too dark.
As far as the Magna transmissions go, I believe they're extremely reliable when maintained. The only issue is the wave spring.

Save yourself some money and put the cooler in and change the oil at 45k instead of 20k (the cost of the cooler is about 1 oil change). Mitsi gearbox oil is about $50 for 5 litres. I have a cooler & a magnefine inline filter. I checked my TL magna after 25k only a few weeks ago (changed last November/ December) the oil is still like new.