Slushbox problem - it's doing "power shifts" now.

The autotragic transmission in my mom's bugeye Impreza has started doing this thing in the last couple of days, where if you're on the gas when it changes gears, the revs fly up between gears and re-engagement is violent - like a "power shift." I also notice that if you keep it floored up to the redline in 1st it will bounce off the limiter for a half-second before changing gears, and it didn't before. Fluid is at the correct level and looks clean. Any ideas? Right now I think the best idea is to keep trying to drive it as long as it'll go and then get a used slushbox.

That would be called shift 'flare' although the harsh reengagement and the bouncing off limiter in first sort of makes it sound like something is applying 'late' vs applying 'slowly'. I'll look for an apply chart for the holding elements and see if anything pops out at me. Does it happen on every gear shift or only certain ones?

Other than low fluid level, that kind of shifting is done when the trans is overheating- if it's a detected fault.

But it sounds like the pressure control is on the fritz.  It has fluid, but isn't able to use it correctly.

Seems like it's happening on every shift as long as I'm on the gas. May be slightly worse when the powertrain is cold. This car does have an AT overheat indicator and it hasn't come on.

Apply chart

pdf describing operation

So if it happens 1-2 and 3-4 but not 2-3 I'm going to guess it's a problem in the band servo hydraulic circuit. 

If it's happening in every upshift I would say it's electronic controls related. 

OK I'll give this thing a run up through all the gears tonight and carefully note which shifts are "flaring."

Edit: Oh one other problem this slushbox has that might be helpful to note: When it's put into reverse for the first time after it's been sitting a while, the engine just freewheels for a few seconds before it gets moving. Giving it some revs gets it going faster, but then it picks up violently so I avoid it.

Enough clutch material in the filter that the pump is not able to keep up with requirements?

Streetwiseguy said:

Enough clutch material in the filter that the pump is not able to keep up with requirements?

Would this cause the fluid to darken? Fluid looks new.

Edit: Oh one other problem this slushbox has that might be helpful to note: When it's put into reverse for the first time after it's been sitting a while, the engine just freewheels for a few seconds before it gets moving. Giving it some revs gets it going faster, but then it picks up violently so I avoid it.

That is probably relevant, and if it happens in both directions (drive and reverse) it may allude to a line pressure problem being the cause of everything.  If the car is always parked in the same spot that always has to be reversed out of you may only notice it in reverse because that's the only place its ever parked long enough to find out (overnight etc). If it truly does only happen when shifting to reverse then both the apply chart and the pdf point to that being a problem in either the reverse clutch pack or the low/reverse 'brake' which is also a clutch pack. In that case it would probably be a separate issue from the flare.

So yeah, if its been parked overnight see if it has a long/delayed engagement into drive, and then see if the flare happens in every gear. If both those things are true it's probably a main line pressure issue. Then you decide whether it's worth trying to fix that.  

No it definitely doesn't have the same problem going into drive.

Sounds like you probably have more than one issue, then. Usually slow/delayed engagement into gear is mechanical issues that require pulling it out and apart. If you don't plan to actually rebuild what's there I would just baby it until replacement with a used unit. You could try throwing some snake oil in it and see what happens. 

I've seen this happen more than once with the 4 speed.

Usually, we send it to our trans guy  and he applies his arcane dark arts and it works correctly.

I have also seen axles break from people just living with it.

So it seems that the problem gets worse as the gears get higher.

First to second is more like a delay than a flare, the revs don't fly up.

Second to third has a bit of a flare.

Third to fourth is really bad.

And all of these problems shifting through forward gears started at the same time.

Got some time to look back at this, so it looks like the shift flares are caused by a "FWD/C" problem and the preexisting reverse problem is caused by a "REV/C" problem.

I've just been lifting off the gas during shifts to smooth them out.

If The Filter Can Be Changed DO so. Any  car will act this way with a clogged Filter. at that Time you can also look for wear, Heat will Darken Fluid and so far you have not seen That.

Start with filter change and cooler flush. Yes it might look clean on the stick but get a few inches worth in a clear hose it might look darker then you think.

OK, so from what I can find there's a spin-on filter plus a filter screen that's much harder to find. Is it important to change the screen or is the spin-on filter enough?

I'd change both, personally.  A blocked up screen will cause pump suction problems.  

Update: Changed the spin-on filter, cleaned the screen and filled it with fresh semi-synth ATF. All the problems are somewhat lessened but still very much there. The mechanic says that it'll need a rebuild/replacement to fix but some fixes in a bottle may be worth a try to help limp it along. He had a car with the same problems and one day it simply stopped going into reverse.

The mechanic recommended this stuff in particular:

https://lucasoil.com/products/transmission-products/lucas-transmission-fix

I’ve had lucas help gimp along a slipping transmission for another year

Update: The problem has disappeared just as suddenly and almost as mysteriously as it appeared. The delay when going into reverse is also gone. So...yay?

Just joining this late.

You dodged a huge bullet, friend.  I think the only thing that saved you was that the flare was accompanied with a hard engagement.  If you get shift flare with partial clutch engagement, it sometimes takes one time to destroy clutches.  It sounds like you got lucky and it was either fully disengaged or fully engaged.

Seriously... lucky beyond words.

I would say that if it happens again, immediately stop, turn it off, have it towed.  I agree that it sounds like a sticking solenoid or servo, or possibly an intermittent wire short.  That can mean instant death depending on how it is actually applying pressure.  Fixing a solenoid or a servo (depending on the year) can be a $100 fix.  Rebuilding the whole thing is more like $2500.  With slushboxes, the cheapest fix is always right now.  If you keep driving it, it gets expensive VERY quickly.

Wow that's scary...the more I learn about slushboxes, the less I like them!

I'm leaning more toward replacement than rebuilding if this transmission becomes unusable. There are only two shops in the country that do rebuilds on slushboxes, and one of them is the total E36 M3bird of a mechanic who wasted years working on my Corolla at a snail's pace while he took on more lucrative jobs.

There are plenty of good shops that will do a 4EAT rebuild just fine.  All 13 of the shops I ran could do them.  It's not like building a TH400.  The Suby transmissions are basically modified Jatcos and they more or less suck to rebuild.  They're finnicky... hard to get them just right, but any good shop can build them.

I'm just thinking that a $100-200 fix right now might prevent you from having to do all the labor of an R&R on a transmission that might be a used time bomb.  Keep in mind that Suby transmissions are not just a quick replacement.  With the transfer case and tight packaging, you're looking at 8-10 book hours... which means $1000 at a shop, or a very long weekend in your driveway.