Keeping your ZF cool

There is much discussion on the internet regarding the cooling side of the ZF gearbox on a falcon. The OEM setup is a heat exchanger on the side of the block using coolant to cool the gearbox fluid.

The alternative is to bypass this setup and run a air/oil cooler, which sits in front of the condenser.

The reason for the many discussions around the place is the fact that the Ford OEM setup has been known to fail in a number of cars. Various polls put the failure rate somewhere around 10%. Personally i think that is an absolute worst case scenario given it hasn't made its way in to any mainstream news over the years, like the focus powershift or territory ball joints. This failure seems fairly random, with a broad range of falcons and territories being affected, however reports have become more scarce in later years. This could be due to the problem being fixed, or just the fact that the volume of cars sold was less. At this stage i haven't heard of any failures in SZ territory or later, or FGX falcon.

Given the cost of the ZF gearbox, which is rendered useless if coolant gets in it, many people have opted to bypass the factory setup in favour of an air cooled setup, thus eliminating any chance that a 'milkshake' can ever occur.

So this is basically the 2 trains of thought. bypass it and eliminate the risk, and assume that the gearbox will still operate fine, or 'run the gauntlet' as some would put it, and stick with the OEM setup.

For those who like to keep their car factory, there some steps you can take to reduce the risk. A member on another forum has suggested the failures are caused by residual casting sand in the block, finding its way into the heat exchanger and causing corrosion. I've had this confirmed by another good source also. To help with this, it is recommended to give your coolant system a good flush, fit a new heat exchanger and refill with Ford coolant at the correct concentrate level.

i priced a new heat exchanger recently and from my dealer it $477 fitted. This doesn't include a flush. They actually drain your system and re use the same coolant. You need to specify if you want a flush as well. My car has had 2 full flushes in its life, so i'm happy for them to do this with mine, knowing any casting sand would be long gone by now.

This i'm told will go a long way to making a failure 'not probable'.

Other reports suggest failures are also caused by the actual unit failing, or from electrolysis.

I believe this problem isn't as bad as what it appears due to the 'small community' that forums are. This can often make problems seem a lot worse.

Thanks mate. Just out of interest, what sort of life are people getting from their ZF Boxes? I know of one that is at 180,000 KMs, and has just started towing a small (3.5m) boat - my first thought was to tell them to service their 'box. This is on a BFII Fairmont Ghia.

The reason i have started looking a bit more in to this is the fact that my circumstances have changed and my car looks like it will have to last me many more years. not really a problem as its a great car and does its job well (family chariot).

Currently i have 160000km on the clock and its pretty much as it left the factory. No signs of any issues with the operation of the trans. ZF recommend 100000km service intervals, and i've been meaning to get it done, but life just keeps getting in the way.

The discussion also came up in the OEM price thread, and i didn't want that one to get derailed too much so i started a specific thread and Norm said he would move any relevant discussion over.

After some investigation i'm told the cooler issue was caused by residual casting sand in some blocks (low number) wearing away the inside of the heat exchanger over time, a good engine cooling system flush as recommended per service intervals will eliminate this abrasive material if it was present.

Rob, it wont be anywhere near 10%... probably closer to 1%...

As we well know, noise on Forums, especially 1 in particular, can tend to magnify "issues"..

Rob, good info thanks mate.
I had seen it on another site but tobh I couldn't be bothered reading it all. Yours is a good summary overall.
Thankfully I don't need to have concerns for my FGX being manual but got to say I think for such a modern day box even though no longer in production if I recall right is pretty lame if having to do preventative maintenance such as having read. Sure I can understand changing tranny oil to by pass the OE design so to speak in view of reducing future issues astounds me.
Residual casting sand - my god.
Using the same oil upon having it serviced but to advise if wishing fresh new oil if desired.
Again my god.
As you say it sounds like its not as bad as prior or blown out of proportion possibly but it really highlights back in the ol days the KISS principle sure made life easier in servicing and longevity - all in the name of progress and yes I am impressed of seamless shifts and countless gearing matched by/to the black box.
It reminds me that we were told long ago computers were the answer to worlds problems.
Very interesting must say.

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Originally Posted by 4Vman

After some investigation i'm told the cooler issue was caused by residual casting sand in some blocks (low number) wearing away the inside of the heat exchanger over time, a good engine cooling system flush as recommended per service intervals will eliminate this abrasive material if it was present.

Rob, it wont be anywhere near 10%... probably closer to 1%...

As we well know, noise on Forums, especially 1 in particular, can tend to magnify "issues"...

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I agree, which is what i said in the last line of my opening post.

The problem is, the cause of failure, by some reports, isn't restricted to that sole cause. Whether or not the other 'causes' are from poor quality product (heat exchanger) or lack of maintenance or incorrect percentage of coolant, or stray current causing elctolysis, is very hard to determine with any sort of accuracy. The point is, because the gearbox is such an expensive item, many people aren't prepared to take the chance.

Some cars have failed very early on (less than 10000km), while others have failed much later in life. Even a coolant flush by itself won't solve the problem if the problem has already started to affect the heat exchanger. This is why the best bet, if you want to keep it factory, is to replace the heat exchanger as well as do a flush.

Quote:

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Originally Posted by prydey

I agree, which is what i said in the last line of my opening post.

The problem is, the cause of failure, by some reports, isn't restricted to that sole cause. Whether or not the other 'causes' are from poor quality product (heat exchanger) or lack of maintenance or incorrect percentage of coolant, or stray current causing elctolysis, is very hard to determine with any sort of accuracy. The point is, because the gearbox is such an expensive item, many people aren't prepared to take the chance.

Some cars have failed very early on (less than 10000km), while others have failed much later in life. Even a coolant flush by itself won't solve the problem if the problem has already started to affect the heat exchanger. This is why the best bet, if you want to keep it factory, is to replace the heat exchanger as well as do a flush.

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Yep.

Like everything that "fails early" of the total number of failures a % will be a component defect issue, a % will be as a result of misuse/poor maintenance and a % will be secondary causes (residual casting sand in some blocks).

Its probably very difficult to know how that is broken up, but depending on how you want to present the information its easy to paint a worse picture than it really is..

Again, i really have only heard of isolated issues with this.

I started a new poll on AFF to try to determine whether or not the problem was still present in later years, and part of the poll was to determine if you had had a failure, whether the cooling system was serviced. However, it didn't take off that well, with me largely being laughed at and told, by the same few, to just bypass the whole shebang and that ford are useless etc etc. Its hard to have an adult discussion sometimes over there, although i do admit, for many it would seem like the same discussion that had been had many times before.

One thing that sticks in my mind, is the fact that no manufacturer that i'm aware of use an air/oil cooler to cool trans fluid. There has to be a reason for this.

Two reasons that I can think of are

Faster warm up times for the oil, when controlled via coolant. We all know cold oil is thicker and takes longer to circulate, so having it warmed as quick as possible is beneficial. An air/oil cooler will take much longer, and some people have reported their ZF misbehaving on cold mornings until it warms up.

Another reason is much more stable temperature of the oil, given its being controlled by a cooling system with a thermostat. Stable temps are much better for these fussy gearboxes.
An air/oil cooler will keep the 'box cool enough, and by some reports it operates a lot cooler than the factory setup, but it is also at the mercy of the ambient temp, so oil temps, while probably not massive, do fluctuate more than if controlled via coolant. I can't say if this has any long term effect on the 'box. People have been running air/oil coolers for many years with no reports of issues, so one would assume in most cases, it is fine.

An air/oil cooler also sits in front of the condenser and partially blocks airflow. This is also pretty minor, but depending on where you drive, could have an impact.

These are some reasons I've come across to keep the factory setup.

Temperature stability and control Rob, as you pointed out.

Tossing cold trans fluid back into a hot trans may shock load components and impact its opperation, everyone thinks they know better than the manufacturers, there will be very good reasons for doing it that way.

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Originally Posted by 4Vman

Again, i really have only heard of isolated issues with this.

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You're on the wrong forum:)

Nevertheless, it does happen. when i first bought my car i was aware of it, but still had warranty so wasn't bothered. The dealers at the time denied it was an issue and claimed it was fixed with the heat exchanger on the block. At least now most dealers are acknowledging the problem does exist and that they have seen examples of it. My dealer still tried to claim it was only early FG's, but failures have been reported well in to FG2.