new (to me) tranny having problems

[Stoney712]

I have a 2002 Outback I bought in '06 with about 75k miles.  It now has 222k miles and the engine still runs strong (no head gasket problems yet, at least no oil and coolant mixing).  I recently purchased a used transmission from a website willing to warranty it.  Subsequent to its installation I drove away from the shop happy it was over.  Apparently, the mechanic did not test drive it at highway speeds, only on in town roads.  When I first got to about 70 mph a terrible noise and "shudder" started and would not stop until I came to a complete stop.  There was some kind of resistance like almost like the rotor was warped, but this possibility was fairly quickly eliminated.  It really felt like the whole car was going to fly apart.  We determined the problem was the U-joints in the prop shaft (even from a second opinion, damned non-serviceable u-joints!).  I obtained a new prop shaft (couldn't get a used one quickly enough and for a price that justified going used) and had it installed.  The same thing still occurred, only it took longer now to show up.  I didn't go straight back to the mechanic's because it was closing time.  I drove the car more that evening at lower speeds where the problem doesn't rear its head, however; when I made a pit stop and parked on a hill the problem "changed".  The hill was enough of a grade that I didn't put the car into reverse to back out of my parking space, I just pushed the clutch in to coast backward.  The car moved maybe 3 feet and stopped like it was in a forward gear; I put it into reverse expecting to hear some terrible clunk like I was ripping some part of tranny out in doing so, but nothing...the car seemed to move on to the next moment as if nothing out of the ordinary occurred.  As I drove a little more this was not the case either.  I began to hear a noise, I believe from the tranny, similar to what you might hear if you ever put a playing card in the spokes of your bicycle as a kid.  It's a cross between that and the sound a bad heater blower fan might make.  This new noise happens in gears 2 - 5 and occurs when accelerating (what I call positive torque) and when I make the engine turn just fast enough to match the spin of the transmission resulting from the velocity I am travelling (what I would call neutral torque).  It does not happen in a "negative torque" condition (the force of decelerating by simply leaving the car in gear and letting off the accelerator, producing torque in the opposite direction of that for accelerating).  My old tranny made a similar noise in the negative torque condition for a long time, and I think was the ultimate cause for the need of a new one.  In dealing with the transmission seller, we have gone through a litany of possible problems, each eliminated one by one.  Their last (or at least most recent) suggestion is that the carrier bearing might be bad.  Any thoughts or additional suggestions?  I think it is still something in the tranny (no idea what internal part) or maaaayybe some issue with the aftermarket clutch installed at the same time.  Oh, one additional note, the high speed shudder went away when the new noise showed up.  Now only a slight shimmy between 68 & 73 mph; feels more like a bad motor mount now but I know that won't cause the new noise.  I don't think the original shudder and noise is motor mount related either because I think it would go away if I slow down.  Additionally I think it would happen in a certain rpm range if it was motor mount related...not at a certain speed.

Sorry for the long narrative, but I think it in needed since responders can't test drive it.

[Fairtax4me]

Manual trans or automatic? Did you compare and match the trans ID numbers before buying the new trans? It's on a white sticker on the bellhousing.

 

It sounds to me like the "new" trans has the wrong final drive ratio. This causes immediate binding of the drivetrain because the front and rear differentials are being turned at different speeds. The center differential is put under incredible stress and has likely failed, which is why the symptoms have changed.

 

If the "new" trans came from a Legacy 2.5i model instead of an Outback it has the wrong final drive ratio.

[ivans imports]

6 broken awds in five speeds in one month sounds like got a bad trans unit the rear berrings go and tears the awd apart check for meatal in the oil or any tiny bitts. the ujionts are replacabble. pn    1-0430 neapco ujiont. Anyway of the 6 i dd 5 were 01-04 outbacks all bad awd seems more commen on outbacks as they are heavyer cars. Also i put 4.5 L of oil in them keeps the awd in oil all the time and makes trans less likly to fail. Have determined that they die from long downhills all the oil ends up in front of trans and backend runs dry overheating the awd unit untill it pops the snapring and eats itself

[Stoney712]

Fairtax| I need to verify, but I think the "new" trans came from an Impreza.  The seller claims they are the same gear ratio...that was the first thought I had after I changed the prop shaft.  I couldn't find anything on either trans denoting anything at all, but I will certainly look again now that I know better what I am looking for.  BTW, it's a manual.  Additionally, is the "middle" differential in the prop shaft or at the back end of the transmission, in the transfer case, if you can call it that on a suby.

ivans| thanks for the input.  Question: with the u-joints welded on, how do I replace them?  Are you confident enough with a mig welder to do that kind of work?  I had heard of some way to replace them but to be honest, the technical labor aspect described by this particular source caused me to glaze over once it seemed obvious, by their description anyway, that it's likely more trouble than it's worth.

Thanks for the leads for completing more homework assignments to resolve this issue.

Edited November 25, 2013 by Stoney712

[Fairtax4me]

Impreza usually had a 3.90:1 final drive manual.

Outback would be 4.11:1 if a manual trans.

They may have same 1-5 ratios, but the FDR is the really important one.

 

Trans ID number is usually on the upper left hand(drivers side) corner of the trans bellhousing right in front of the starter. Either on top or on the side facing the strut tower.

 

Center diff is in the extension housing of the trans. The section between the tail housing and the main case. Often referred to as the "transfer housing" since it also contains the rear transfer gear shafts.

[ivans imports]

the ujionts are peened in i push them past the peen and the new ujiont has internal clips that hold it in is no problem takes me 20 min to change it have done many of them. +1 impreza 3.90 outback 4.11 tooth count time. Ask supplyer for the matched impreza rear diff