4EAT slips above 2500rpm

[Mystery Meat]

Hi everybody,

 

I just got my first Subaru, a 1991 Legacy L wagon AWD, and Im having troubles with the automatic transmission in it.  I knew it had trans problems when I bought it, but the previous owner was not very mechanically inclined, and couldn't describe the problem very well.

 

So, after I got it home, and checked it all out, I have come up with this so far:

 

PO had the trans fluid changed, and fluid looks brand new.

 

Trans fluid was a wee bit over full when checked correctly.  (operating temp, shifted through gears, level ground)

 

The car will shift through all the gears with no hesitation, including overdrive (and hold them).  But it will only stay in gear up to an average 2500rpm.  Above that, rpms sky rocket like it was shifted into neutral.  

 

It will shift into the next gear when rpms come back down.

 

I say average, because when the trans is cold, it will hold a gear nearly to 3000rpm, and when hot, it only holds to a little above 2000rpm.

 

Hoping to avoid a full rebuild for now.  Any ideas?  Thank you for your help.

 

 

[ivans imports]

Try addjusting band but probly to late forward clutch pack or band

[Fairtax4me]

Just Find a low mileage junkyard trans and swap it out.

[1 Lucky Texan]

long shot but, what if PO used wrong fluid?

[idosubaru]

i believe these early 90 and 91 legacy auto's had an issue with the transmission cooler or lines close to the radiator getting clogged up with debris.  i think Subaru even made a kit for repairing it and/or installing a filter to keep them from clogging.

 

as a temporary test you can simply buy a piece of hose and install one end on the outlet side of the transmission fluid line and then the other line on the inlet side of the transmission fluid line - making one big loop and bypassing all filters, radiator, lines, hoses, etc.  if the transmission then shifts fine then you know that's the issue and it only costs a few bucks in ATF hose which is easily used down the road anyway.

 

might be other ways to test but i'd highly suspect this clogging issue since it's a 90/91 thing.

[NorthWet]

No solution, but similar issue with my 92 SVX.  Pretty much as OP posted:  The issue seems to be running above that engine speed (mine is around 2900rpm).  As a get-around, I readjusted my TPS to convince my TCU to upshift at a lower RPM, then just drove the car very conservatively.  With 230HP easier to loaf the engine than with a Ej22...

 

It has been a couple years since I pulled tranny codes on this one, but I think that the only code was for a duty-A solenoid.  Perhaps the main line pressure was exceeding a limit and the tranny was protecting itself.  Pure speculation.