The filter protects more than one part of the transmission - But the point I'm trying to make in the context of this thread (and possibly failing with you?) is that the filter in the transmission is performing a different function than the filter in the engine.

The filter in the engine behaves like an automotive liver - all of the oil (or very nearly all of the oil - some might get trapped) is actively passed through the oil filter in a circuit. The engine oil gets "cleaned" by this filter.

I don't think that the filter in the transmission is performing the same function. The filter here is behaving more like a condom than a liver. Whilst the front pump sucks oil through the filter and pushes it through the valve body the "flow" through the filter is minimal when you compare it with the flow through an engine oil filter. The filter is therefore there to stop the nasties from getting in; much like a condom.

Same is true for the transmission. All fluid going to the pump goes through the filter first. The pump is solely responsible for moving fluid to the working, regulating, lubricating and cooling circuits.

Your theories about splash lubrication and partial filtration are highly imaginary. And misleading. The ATF filter is just as much "full flow" as the typical engine filter.

The physical location of the filter is highly irrelevant. What matters is its position as it relates to fluid flow. It is almost impossible to get a handle on fluid flow by looking at the transmission itself. It's a lot lot looking at a circuit board and saying "I don't see any electrons moving."

I think it is more like looking at a circuit board and saying oh look there's a big fat resistor...

But anyway it looks like we'll have to agree to disagree on this one.

wait a minute, before you just agree to disagree...

please expound on your thoughts of why it's different from engine oil filter?

do you mean to say that since the oil pan is in contact with the bottom of the transmission, that oil is not being filtered due to splash from the pan?
the pump pulls oil from the pan, and pumps it throughout the transmission, and filtered oil falls due to gravity back to the pan.

I do see that the transmission is different from a DIESEL oil filter, due to the lack of a bypass soot filter, but the transmission has no soot, so that's not needed... aside from that, I don't see a difference... I'd like to understand what you see different.
thanks.

John, those filters you've seen torn....how long had they been in there?

Unlike the foam filters used on some applications, the filter for the 722.3/4 transmission is very well constructed and not reasonably subject to tearing or "pulling apart."

OK John seeing as you asked!
 

No!

Right John – I'll try and explain what I think is happening.


(Boy am I pissed off with ATSG that they don't have a proper explanation of operation chapter in either the 722.1 or 722.3/4 manual. I don't have access to the paper FSM version that has a chapter on automatic transmissions so I can't check to see if there is a description there.)


The purpose of the front pump is to provide hydraulic pressure.


The output from the front pump is connected to the valve body.


Springs and pistons in the valve body react to the pressure produced by the front pump.

EDIT:- The governor that is attached to the output shaft of the transmission controls when shifting should occur

For example, at a certain input shaft speed – somewhere in the valve body - a spring and piston reaction force will be overcome by a force due to the pressure created by the front pump. So a spring and piston will move at a certain speed...


...this spring and piston will be connected “hydraulically” to an actuator that will move either a brake band or a clutch. Gripping hold of parts or releasing parts of the sun and planet gears in the transmission is what changes the gearing – in other words the relationship between the input shaft rotational speed and the output shaft rotational speed.


The motion – the distances travelled – by the pistons and springs in the valve body are small. (Have a look at the pictures I posted in this thread http://www.peachparts.com/shopforum/diesel-discussion/304903-722-118-automatic-transmission-rebuild-monster-diy.html) The volume of fluid pushed out of the valve body (due to movement of the springs and pistons within) is correspondingly small. I think that this type of movement of fluid through the valve body or “flow” is the only way in which fluid leaves the pressurised side of the front pump.


This type of “flow” is not equivalent to that of the “cleansing” situation of an engine oil pump (be it a diesel engine or not). This type of flow / movement of fluid through the valve body only occurs when it is time to change gear.


As the transmission filter is only connected to the input of the front pump it therefore does not perform a task that is similar to the “cleansing” process in an engine. It is behaving like a condom – it is just protecting the parts that are upstream; where the valve body is arguably the most crucial part. It is not behaving like a liver where all of the fluid (in the transmission) gets the treatment.




Phew! Deep breath – tea break.




Now you could argue that pressure is tapped off from the front pump and used to make sure that the moving parts in the gear set are nicely lubricated. My problem with that line of thought is that in the 722.118 transmission that I rebuilt and in the 722.120 transmission (that's also in bits) in my garage I can't see any evidence that the front pump does this job. The valve body only connects to the actuators. It doesn't have an oil supply line that goes to the bearings for example.


Besides why do you need this type of system in a gear box? Manual gear boxes and differentials don't need a pressurised fluid system to keep them lubricated.


You could also argue that the flow through the filter and the front pump is much greater – that the filter filters all of the oil in the transmission much like the lubrication system in an engine. Again, I have a problem with this line of thought, as I don't see an output from the “front pump system of plumbing” that would enable that kind of flow. I would expect to see an orifice of similar size to the input (shown in the pictures posted previously in this thread). If the front pump was for filtering and filtering alone you'd want to pump through as much fluid as possible – the exit hole would be obvious – you wouldn't mess about with piddly little passageways like the ones in the valve body.


From my observations of the piddly little passageways in the valve body I have reached the conclusion that the front pump is only used for one purpose – to represent input shaft speed as a function of hydraulic pressure. I don't think it is there for anything else.


(In desperation I will repeat that) The valve body uses the pressure produced by the front pump to move actuators that clamp onto the sun and planet cog systems in the gear set so that the transmission can change gear. The motion of the valves within the valve body are small and displace a small amount of fluid – which is why I think the transmission filter is performing the job of condom rather than liver.


I'll try and make it as clear as I possibly can (before I just give up and agree to disagree):-


I think the front pump is there to produce hydraulic pressure – it is not there to pull fluid through the filter.


@everyone:- Whether you agree with or not is my text clear and understandable?

Certainly, the main function of the pump is not to pull fluid through a filter. (The same could be said for the engine oil pump.) But that doesn't change the fact that all fluid pulled out of the sump is pulled through the filter.

Additionally, your theory of "almost no flow" is quite flawed. The operations manual for the 722.3/4 transmission identifies a total of eleven hydraulic circuits by pressure. Each one of those circuits is regulated by a relief valve. That regulation results in significant flow, even in a steady-state condition. Additionally, flow through the torque converter and to the cooler is continuous.

What do you believe is the source of said hydraulic pressure?

I disagree with this for the case of a 722.1/3/4 transmission. I see no evidence that that happens.

A hydraulic system without relief valve(s) would be very poorly designed.

A hydraulic system that would allow flow to the extent you suggest would also be poorly designed. High flow rates through restricted pathways is something to avoid in hydraulic design - hydraulic design engineers want to avoid cavitation.

A relief valve is not designed to be always open.

I see no evidence that the cooler is connected to the torque converter.

You see no evidence that the pump draws fluid through the filter? The 722.3/4 Operating Manual shows plenty of such evidence. You should look at it.


Same could be said for a system without good filtration.


They are not designed to never open, either. Consider that ten of the regulated pressures in the 722.3/4 transmission are reductions of working pressure, as supplied by the pump.

Take a closer look at the lubricating pressure system. Fluid leaves the torque converter then goes to the cooler before being returned to the transmission in a cooled condition.

That's not what I said - I see no evidence that ALL the fluid gets pulled through the filter.

The filter that is connected to the front pump isn't designed to perform a cleaning function for all of the oil in the transmission.

Of course they aren't designed never to open - that would be silly. Then it wouldn't be a valve would it?

Relief valves are designed to open at a predefined pressure. They are there to protect systems and stop damage.

No it doesn't. The oil cooler is only connected to the front pump.

Nothing like being an advocate for something you haven't seen!!!


That might be why you are so confused.


Here is a direct quote from the Operations Manual:

The lube oil flows from the flow-off edge of control valve-working pressure to torque converter, from there to the oil cooler and back again to the transmission.

Army and TangoFox007, you guys are making this almost as fun as an oil thread! ;)

Army is so convinced that the transmission filter is just a decoration, I am waiting for him to recommend that it be removed and polished every six weeks.

What do you mean? This is an oil thread!