Do transmission filters on a healthy transmission get clogged? - PeachParts Mercedes-Benz Forum

shertex · #1 10-18-2014, 04:39 PM

Just thought I'd solicit the input of some more knowledgeable types than I on the question as to why the filter on a healthy transmission needs to be changed. If the reasoning here is flawed, why is it flawed?

DO I need to change my transmission filter? | Expert Advice from leading Fast Lube suppliers

Transmission filter changing

Customers often ask if they should change the filter as well as the fluid.

In the past, automatic transmission fluid was changed by removing the pan, changing the filter and gasket and refilling with 1/3 the capacity of the transmission. This was the only method known to change the fluid so it was the acceptable method.

When transmission flushing equipment was introduced to the market, people started to ask, “what about the filter?” “we used to change it, why don’t we have to change it now?” The answer to this is, it was changed before because we already had the pan off so “we might as well” plus the filter company’s packaged the gaskets with filters and encouraged this practice.

An automatic transmission is a closed hydraulic devise with no foreign matter being introduced. Therefore, if the filter on a transmission should ever become plugged, it is plugged with transmission parts! This means the transmission is past the point of needing a fluid change. An engine on the other hand is constantly exposed to foreign matter (air and fuel) which brings in contaminants as well as the combustion that creates many other byproducts. The engine oil filter is designed to filter these products out.

Many transmission manufacturers use only a screen on the fluid pickup to filter out any casting flaws or debris that could be poured down the dipstick. Some manufacturers do not recommend changing the filter.

The fluid will break down and needs to be changed, the filters do not plug up on a healthy transmission.

bsmuwk · #2 10-18-2014, 05:07 PM

I've never had it happen, I seriously doubt a healthy transmission could clog a filter.

Usually when they get dirty enough to clog you've had some sort of failure internally.

pmckechnie · #3 10-18-2014, 05:15 PM

My opinion for what its worth.

Our transmissions were designed with a filter. It needs to be replaced when the oil is changed. The company you referenced sells transmission flush equipment. If you have to pay to have the flush done and the filter changed you would be better off doing it the old way, drain and change.
A good friend of mine has a transmission shop and he says the flush machines are the best thing that has ever happened for his business. He still services transmissions the old way but he also flushes the torque converter, similar to the way the flush machines do it.
So if it has a filter, change it when you change the trans fluid. Also change the oil filter, air filter, power steering filter, cabin filters and any other filters at the proscribed times. You car will love you for it and give you many years of service.

PaulM

vstech · #4 10-18-2014, 05:28 PM

Clutch material? Aluminum and steel worn surfaces...

If filters don't need to be changed, why put them in?

On the MB, the entire fluid capacity can be drained. The torque converter is equipped with a drain plug.

shertex · #5 10-18-2014, 05:34 PM

OK, so even healthy transmissions will produce wear particles which, in high enough quantity, could clog a filter.

Related question: what about trannies that don't have a filter? Are they sub-standards designs? And then there's our 02 Odyssey that apparently has a filter (very difficult to access) but Honda does NOT recommend replacing it.

shertex · #6 10-18-2014, 05:38 PM

Also...I know MB quickly backed away from their "sealed for life" approach on the 722.6....obviously fluid needs to be changed. But if they knew full well that even healthy transmissions produce some debris, why would they have asserted sealed for life in the first place? I suppose the answer could be that it was simply a marketing scam....but still.

shertex · #7 10-18-2014, 05:41 PM

Quote:

Originally Posted by vstech

If filters don't need to be changed, why put them in?

But that's precisely what MB did when they originally released the 722.6.

97 SL320 · #8 10-18-2014, 06:15 PM

A low to mid time transmission should not have any material in the pan / filter. However, mid to high time units that never had a filter change could start to clog with clutch material even though the trans is otherwise in good condition. There are more friction discs in a modern trans that in years past but filter size hasn't always increased.

The biggest issue is the filter does not have a bypass valve, as the filter gets restricted, cavitation sets in, pressure drops and an otherwise good trans starts to fail.

Now, if the trans is driven until it stops moving and a filter change revives it, I'd say that trans won't last much longer.

The only real way to tell if a filter is clogged is to look at suction pressure ( vacuum ) between the filter and pump,

w123fanman · #9 10-18-2014, 07:18 PM

With some auto transmissions, such as the ones in W123s, is it really worth not changing the filter? It's $14.25 for the Elring filter and gasket on Pelican. Seems like it doesn't make sense not to change it on those.

shertex · #10 10-18-2014, 07:23 PM

Interesting reading on Odyclub (a Honda Odyssey forum)...countless owners have asked the dealer about replacing the transmission filter. They are consistently told either (a) it doesn't have a filter (but they do from 2002 on) OR (b) that it doesn't need to be replaced.

Fairly difficult to access....MB piece of cake by comparison.

Really odd that there's no maintenance interval for that filter....mine's been in there 184k miles!

97 SL320 · #11 10-18-2014, 07:36 PM

Some Hondas just had a coarse screen on the suction side of the pump that was not accessible unless the trans was split. In that event, I'd add a spin on or inline filter ( looks like a fuel filter ) to the return side of the trans cooler. The inline filters are used by trans shops to prevent material from leaving the trans cooler post rebuild and causing problems.

Spin on filters are used in hydraulic systems / larger trucks / machinery.

mannys9130 · #12 10-18-2014, 11:26 PM

I highly doubt a tranny filter could clog completely to the point of impaired function. That's a LOT of crud we're talking about. I agree, a trans is a sealed hydraulic device. I would say for the first trans service at 30k miles or 60k miles, a pan-off filter change is a good idea. That replaces the OE filter which caught the debris created during initial break in. It also allows you to remove metal dust from the pan magnet and give it the best ability to catch shavings for the life of the transmission. After the trans has its 2nd filter installed and the OE fill has been replaced, I believe only fluid exchanges are all that's needed for proper maintaining of the trans. The transmission fluid is what oxidizes, shears, and depletes additives as well as suspend small particles of debris too small to stick in the filter media.

Automatic transmissions have much more "stuff" going on inside than a differential or manual transmission, but those 2 things don't have a filter. LSD diffs and transaxles have clutches inside them, and no filter to catch it. Synchros make brass shavings that are sloshed around by turbulance. Those shavings are big compared to clutch dust...

All I'm saying is, I agree with the literature posted in the OP. I think at the initial service, a pan-off filter R&R is good insurance, but no benefit will be seen after that. Change the fluid on time, keep it cool, and it'll last as long as it possibly can.

shertex · #13 10-19-2014, 08:40 AM

FWIW here's the opinion of the tech who does my oil analysis:

Absolutely true. This has been on-going in industrial applications for years in components where environment, temperature, humidity, no combustion are all stable. In the future, transmissions will be sealed for life as oils continue to get better and better. The filters in most cases only catch the large stuff and if that is present, failure is not far off anyway. Any filter is the most efficient when 80 percent clogged. In years past I have always used a Mityvac to extract all I can from the sump and if performed regularly the oil in its entirety is getting renewed.

EDBSO · #14 10-19-2014, 11:25 AM

Quote:

Originally Posted by vstech

If filters don't need to be changed, why put them in?

.

Nicely said +1

A study sponsored by Hershey found that chocolate did not cause acne.

Another study sponsored by Philip Morris found that cigarettes do not cause cancer (this is true, smoking them does!).

I would not trust a transmission flushing company's opinion on filters farther than I can pitch their equipment.

DeliveryValve · #15 10-19-2014, 03:38 PM

I have come to know that flushing without filter changes is an acceptable practice among reputable shops. Their theory if there are particles in the trans, you have bigger issues than a fluid change would fix. Some will change out the filter after 120k or so. But most part, they will not change a filter for the first 100k or so if the trans was flushed regularly.