Aisin TF-80 / AM6 oil, cooler and filter modification project.

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EDC5
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Aisin TF-80 / AM6 oil, cooler and filter modification project.

Post by EDC5 »

Actual Project begins page 4


Not sure if this is the correct place to start a project thread but since the AM6 is fitted to Peugeot and Citroen models it didn't make sense to confine the post to one of those sub forums.

So, those of us with the AM6 gearbox are familiar with the requirement to change the oil semi-regularly in order to preserve the bores in the aluminium valve block. If left, the contaminated oil will allow the bores to be worn wider leading to harsh gear changes and increased wear.

Changing of the oil in these gearboxes (like many others) is an incomplete affair with much of the contaminated oil remaining in the box; therefore a few consecutive oil changes are required to get the oil clean again. I have done the oil change 3 times now and whilst the oil that is left in the box is a lot 'redder' than the black filth that I drained out, its not exactly pristine so a fair bit of the crud is, I'm afraid, still in the gearbox.

Apparently there is an oil filter for the gearbox however it is inside the gearbox and cannot be changed without the removal of the entire thing.

So, my idea is to fit an external transmission oil filter to the gearbox, this way the level of crud in the oil can be more easily controlled without throwing gallons of new expensive oil down the drain à la the current oil change method.

The first issue is that the AM6 on PSA vehicles is not fitted with an external oil cooler that other manufacturers (volvo, GM) use. Instead an oil/water heat exchanger is used like this:
377502e3eaa801bec47b7a460ed75710.png
Whilst this doesn't give the best cooling capacity to the gearbox it does allow for rapid warm up as the gearbox can be warmed by engine water and reach it's operating temp quicker; this is a feature I want to retain with any solution.

I have found a possible solution, a sandwich plate:

Image

Apparently this sits in-between the current oil heat exchanger and intercepts the oil on it's journey back to the gearbox. My plan would be to fit an inline oil filter fed from this sandwich plate.

Here is a diagram of the sandwich plate in situ:

Image

Instead of an external cooler I would be fitting an inline oil filter.

If anyone has any suggestions I'd be grateful to hear them.
Last edited by EDC5 on 20 Jun 2020, 13:09, edited 3 times in total.

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white exec
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Re: Aisin AM6 oil, cooler and filter modification project.

Post by white exec »

I did something very similar on our 2.5 XM, for different reasons. One, then another, of the OE (Valeo) oil-water heat exchangers (sandwiched under the engine oil filter) perforated and failed, filling the cooling system with engine oil. After the second failure, decided enough was enough, and so fitted a take-off sandwich plate, and a Setrab radiator-type oil cooler. The sandwich take-offs were available with or without incorporated thermostats. All has worked perfectly since, the job done around eight years ago.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by EDC5 »

white exec wrote:
11 Feb 2018, 20:02
I did something very similar on our 2.5 XM, for different reasons. One, then another, of the OE (Valeo) oil-water heat exchangers (sandwiched under the engine oil filter) perforated and failed, filling the cooling system with engine oil. After the second failure, decided enough was enough, and so fitted a take-off sandwich plate, and a Setrab radiator-type oil cooler. The sandwich take-offs were available with or without incorporated thermostats. All has worked perfectly since, the job done around eight years ago.


Very interesting. hopefully engine oil / water heat exchengers fitted today are a bit more robust.

In this case I only want to use the oil take-off for filtration purposes as to my knowledge there aren't any overheating concerns with the transmission fluid with the AM6.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by white exec »

It should work. If you're going to use an engine-type oil filter, it might be worth just checking what sort of pressure that transmission is knocking out at the existing heat exchanger. Just thinking that engine oil filters are designed to operate with something like 3-4bar behind them, and unsure what sort of flow they'd manage should the pressure be a much lower figure. Maybe there are external filters specifically for transmissions?

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by EDC5 »

That was my initial plan, use an external oil filter housing, something like this:
RFH4_XL[1].jpg
it can be used with the FRAM HP-1 filter which filters to 18 microns.

I'm going to have to do some research as to the optimum filter size, but 18 microns is better than nothing surely.
white exec wrote:
11 Feb 2018, 22:42
If you're going to use an engine-type oil filter, it might be worth just checking what sort of pressure that transmission is knocking out at the existing heat exchanger. Just thinking that engine oil filters are designed to operate with something like 3-4bar behind them, and unsure what sort of flow they'd manage should the pressure be a much lower figure. Maybe there are external filters specifically for transmissions?


I'm assuming the flow at least would be a lot lower on a gearbox however the pressure might be as high, yet again more research needed I think.
Last edited by EDC5 on 20 Jun 2020, 13:21, edited 1 time in total.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by EDC5 »

After a bit more research I have found that others do indeed fit an external gearbox oil and that it's not a completely daft thing to want to do :rofl2:

It seems more popular with American pickup owners and some kits are available. (http://www.dieselsite.com/dieselsitetra ... mTFIK.aspx)
Interesting excerpts from that link:
Automatic transmissions have internal filters designed to capture only large particles. These filters are designed as a pickup to keep large particles from flowing through the transmission.

The fluid will have clutch dust and other impurities which are all normal in any automatic transmission. This dirty fluid would be recirculated back to the pan.

With our kit you can catch dirty fluid BEFORE it makes it back to the pan. Keeping the fluid clean, keeps your valve body clean which keeps your transmission shift quality at its highest.
My main issue was choosing an appropriate filter for the application. Filter housing I want to use (the FRAM one) takes FRAM HP-1 oil filters, this particular filter is good however the internal bypass pressure seemed a bit high. Ideally I want as small a restriction as possible should the filter become blocked.
I found this excellent website that allows you to cross reference oil filter fitment: http://www.oilfilter-crossreference.com ... t/Fram/HP1

There appeared to be hundreds to choose from but in the end I settled on a K&N Ps-3001 (https://www.knfilters.co.uk/search/prod ... od=ps-3001)
This is a "performance" oil filter so whilst its filtration isn't the best, the flow characteristics are very good, exactly what I need first off.

If this endeavour is successful I may consider changing the filter at a later date with a more effective one, but first off I'd like to have the minimum oil restriction whilst the bulk of the crud is collected in the filter.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by xantia_v6 »

EDC5 wrote:
14 Feb 2018, 09:48
Automatic transmissions have internal filters designed to capture only large particles. These filters are designed as a pickup to keep large particles from flowing through the transmission.

That might be true of American designed transmissions (it certainly is of the older ones), but I don't think that it is true of modern European and Japanese designed transmissions, which do have proper filters.

I believe this to be an image of an AM6 filter, which is certainly not a coarse screen: Image

I am not sure if you know (I did not notice you mention it) that the transmission cooler is (as far as I know, in every transmission) fitted after the pressure relief valve in the line returning surplus oil to the sump. This means that the oil cooler does not see any significant pressure, and that line would not be particularly sensitive to a bit of extra back-pressure.

Another think to think about, (if the transmission already has a proper filter) is that any debris generated in the transmission is going to end up in the transmission sump before it sees any filter, and then next time around, it is going to go see the OEM filter before it has a chance to get to the retrofit, so if the OEM filter is doing its job, there won't me much to catch in the retrofit.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by EDC5 »

Very interesting, I should have given the Japanese more credit when designing the filtration system on these gearboxes then :lol: . If only they had fitted an external filter so that it could be replaced without complete disassembly :(

I understand your point and agree that the oil is sucked into the pump via the filter and then pumped around the gearbox and that all the crud should stay in the sump.

My main issue is that I've flushed the oil twice now and there is still a high content of 'black' in it (initially it was as black as used engine oil). Either it is because there is loads of clutch material still suspended in the fluid or the oil is overheating (or has done in the past) and gone black.

Either I'd like to fit an external oil cooler (like Volvo do with the same gearbox on their cars) to reduce the temperatures and prevent burning of the oil, or, experiment with an inline filter for a few hundred miles and see if anything becomes trapped in it.

One final thought, since I kept hold of the old gearbox oil I might try pumping that through an oil filter just to see if it's effective without messing with the car first off.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by Hell Razor5543 »

I think your last thought is probably the best first action, so that you can see how things work, and what is the best way to proceed.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by white exec »

Although it will certainly trap particles of any size, I'm not sure that an (external) filter will do much to lessen the blackness of the fluid. On a car engine, blackened oil enters the filter, and leaves it just as black.
The blackening of ATF must be either burning or friction-material debris - on a manual box, the oil can run for years and remain the same colour it went in.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by EDC5 »

white exec wrote:
15 Feb 2018, 15:58
Although it will certainly trap particles of any size, I'm not sure that an (external) filter will do much to lessen the blackness of the fluid. On a car engine, blackened oil enters the filter, and leaves it just as black.
The blackening of ATF must be either burning or friction-material debris - on a manual box, the oil can run for years and remain the same colour it went in.


That's true, although the black in engine oil is soot particles if I’m not mistaken, probably less than a micron. What I don't know is if the black in the ATF is overheated oil (inadequate cooling) or from worn clutch plates. The car has only done 63,000 miles so I doubt if the clutches are too worn.

If the colour is from overheated oil then it can’t be filtered but if it's from clutch material then a filter should help somewhat, even if only a small fraction of the crud gets passed the first filter.

Another big advantage i can see with fitting the sandwich plate is that it allows me to exchange the oil, old for new, using the two hoses (which is the procedure Volvo use) instead of flushing endless amounts of new oil through it.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by xantia_v6 »

You can tell if the colour of the fluid is due to burning or micro-particles by dipping a paper towel in some. The fluid will wick up the paper, carrying burnt colour, but larger particles won't move far up the wick.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by xantia_v6 »

I also believe that the transmission will throw an over-tempersture fault well before the bulk temperature of the oil gets to burning point. Burnt oil is usually a by-product of overheating in a slipping clutch, due to abuse or another fault.

I agree that a replaceable filter would have been a very sensible design choice.

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by EDC5 »

xantia_v6 wrote:
15 Feb 2018, 18:15
I also believe that the transmission will throw an over-tempersture fault well before the bulk temperature of the oil gets to burning point. Burnt oil is usually a by-product of overheating in a slipping clutch, due to abuse or another fault.

I agree that a replaceable filter would have been a very sensible design choice.


This is what I've always suspected, I can't imagine with my engine that the oil has ever got hot enough to 'burn'. I always thought that modern Autos with a lock up clutch didn't produce too much heat anyway.

One advantage of having an external filter or remote mounted oil radiator is the increased oil capacity causing the crud to be much more diluted.

There's a good blog here which details a front mounted oil cooler mod with the same gearbox on a Alfa 159, very interesting reading.

https://jabawoki.com/2016/01/27/alfa-15 ... ification/

I must admit, a few parts have already been ordered and I'll update the thread when they arrive :)

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Re: Aisin AM6 oil, cooler and filter modification project.

Post by NewcastleFalcon »

Reading the thread with interest. I have just ticked over to 190,000miles on my Vectra with the same Aisin 6 speed auto box. Thats 130,000 miles on the same transmission oil since a rebuild at 60,000 miles and an external oil cooler fitted. Touch wood the transmission is working as it should no complaints.

I have considered doing a transmission oil change, but I have an underlying irrational fear that the introduction of new fluid, to the 130,000 mile fluid from the communal vat unknown parentage put in at rebuild time is going to precipitate an unnecessary failure of the box, and effectively scrap the car.

Regards Neil