AW55-50SN woes-easy to repair? Topic is solved

[pierrox]

Unearthing this long thread (long time reader but it's my first post!) as I think my auto-trans is suffering from this filter clogging.

Short presentation: I bought my first modern car a couple of months ago, a Saab 9-3 with the AW55-51SN auto-trans. It has 260000km on the clock (about 150k miles I guess). It's new to me to have a car that's less than 20 years old (other rides are a 1986 VW Vanagon, a 1976 Bay Window camper and a 1988 K75 BMW motorbike.

Bought the Saab knowing it had an issue with its auto-trans (clonk from 3-2 and 2-1 when warm/hot), and went through all the steps: flushing the ATF several times (did nothing), swapping the valve body with a good one from a known donor. It worked for a couple of months, that solved 99% of the issues. It still had one specific problem, it would skip out of torque-converter-lock (is this a word?) when torque accelerating on the highway (when you're doing 70-80mph and you want to get to 90-95 and you put the pedal only half way to the floor). I guess it was what you'd call "mini flares". Obviously I was aware of it so would avoid. Then I installed an external filter, having read about the benefits of it, also the idea was that it would be a first step to add an external cooler too. Following this, I did another flush.

But soon after, it started to do some serious flares on 1-2 and 2-3. To the point that I have to drive off grandpa style, and once in 3rd it's fine. Sometimes, on first start of the day, it stays stuck in N (whether I'm in D or R), and if I restart the engine it works.

I think the trans is close to its death, probably didn't see much love during its life. I'd like to give it a few more miles so I can decide to have someone redo it, or swap it. Talking to an auto trans expert, he mentioned the clogged filter (I knew there was one that you can't access) and that one effect was what I'm describing. In short, he told me the problem is that there isn't enough pressure in there to hold the clutch(es) down. Thinking about it, he could be right, and me adding an external filter probably reduced the ATF flow even more, bringing the pressure below the required level. I will by-pass the external filter to see if the theory holds.

So with this new info, Google brought me here. I'm very tempted to give this "added-hole" a shot, at this point my trans is probably beyond repair. Having read the 23 previous pages, I get the idea quite precisely: drill a hole, pierce holes through the filter to unclog it. But having done more research on this idea, I came across this PDF (haven't managed to find the original thread unfortunately) where the guy inserts a bottle cleaning brush through the added hole to clean the filter:
https://www.swedespeed.com/attachments/ ... df.144887/

Anyone here has tried this approach?

Also, I'm going to take the valve body out for further inspection, can I access the filter from there? At least to poke holes into it more comfortably than from underneath?

Thanks for helping those (now) old cars on the road!

[dikidera]

The takeout from the pdf is that it isn't worth it as even that guy eventually rebuilt it(under 400 miles since cleaning), if the filter is clogged, the clutch packs are gone as per his own words. Probably more evident from your swap of a valve body doing nothing permanently, though you didn't say if you cleared the adaptations.

For the record, I now believe a drain and fill is for preventative measure rather than cure-all, in my opinion if any refresh of the fluid does nothing, then the issue is mechanical, whether valve body and/or clutch packs(or other things).

Probably need a new trans. If you have money to spare, just buy a working one, have it refurbished entirely with new clutch packs and valve body and then just swap the two transmissions.

[pierrox]

Thanks!
Yep I did a reset/readapt after the valve body swap and recently when it started to do this.

You're right. My thinking is that if I can get a few couple of hundred miles out of it whilst I get the spare transmission refurbished, it would be worth spending some time drilling underneath. It seems a relatively painless operation, for sure less involved than swapping the entire transmission, which I only want to do once.

[jonesg]

volvo diesel clutch job but you get the general idea. no drama.

[precopster]

After doing the drill hole and piercing of the trans I got a further 30k kilometres out of it before solenoid 2 totally failed (unrelated to the piercing). I ran a Magnefine filter inline with one of the trans cooler hoses and it was great.

Then the heater core failed, then the ABS system was totalled so it was time to get out.

Good luck with the repair of your Saab!!

[pierrox]

Thanks!
I forgot: you had an external filter, correct?
I have a feeling that at the moment my external filter plays a part in the problem. My theory is the internal is clogged, so pressure is reduced. And then, the external filter adds another drop to the pressure - especially as I placed it where I could, which is on the other side of the engine bay, adding probably about 1.5/2 meters of hose. I'm going to bypass it to verify my theory.
But if I drill and pierce, I will have to have the external, correct? Otherwise, all the crap sitting against the internal filter will float around, doing worse things, right?

[precopster]

Interestingly when the trans stopped working I could blow air backwards down one of the cooler lines and manage to get the screen unblocked; it would last until I drove around the block until it blocked again.

What type of external filter are you using? If the internal filter is blocked the trans is toast unless you pierce the casing or remove the trans and disassemble it fully to access the filter, then replace it (you might as well do a full rebuild while you are in there).

You do need some type of filter.

[vtl]

Thanks!
I forgot: you had an external filter, correct?
I have a feeling that at the moment my external filter plays a part in the problem. My theory is the internal is clogged, so pressure is reduced. And then, the external filter adds another drop to the pressure - especially as I placed it where I could, which is on the other side of the engine bay, adding probably about 1.5/2 meters of hose. I'm going to bypass it to verify my theory.
But if I drill and pierce, I will have to have the external, correct? Otherwise, all the crap sitting against the internal filter will float around, doing worse things, right?

Valve body divert only a part of fluid to the cooler. Cooler plays no role in line pressure.