96 Legacy Outback 4eat Trans Noise. Need Advice!

[steamin53]

96 Legacy Outback 4eat Trans Noise. Need Advice!
I'm hoping for a response from someone really knowledgeable about the 1996 version 4EAT transmission and/or torque converters.

Our 96 Legacy Outback has 250,500 miles on it. The transmission in our car is one that I obtained at about 200,000 from a donor vehicle with 70,000 miles on it in replacement of the original which had a torque bind issue only. (I figured at 200,000 miles I should go ahead and replace it).

We recently had a front transmission seal fail in the donor tranny due to a worn bushing on the transmission input shaft. The transmission fluid contained a very fine brass powder like gold dust which the transmission shop felt was not a problem. After replacement of the bushing and seal the seal still leaked. Removal of the torque converter the second time indicated that the shaft was worn sufficiently to cause the new seal to also fail. We also replaced the bushing a second time as a preventive measure and replaced the torque converter in the donor transmission with the converter from our original transmission which I had kept for parts.

Once installed, the transmission would produce a slight high frequency (not pitch) ratching sound in 4th gear only when accelerating and coming out of lock-up which would stop as soon as the torque converter locked up again. The transmission did not make any noise with the original converter. The sound was almost so subtle that one could not hear it and actually sounded like an air leak on a faulty window seal. No other performance issues existed.

The transmission now produces the ratching sound at shift from 2nd to 3rd just at the shift point and then the noise stops. It still present in 4rd gear at all speeds when under load (i.e. not when coasting). It still stops completely once the torque converter locks up in 4th and returns once the converter is unlocked as in passing a vehicle. It is never present in 1st or 2nd gear. The noise is increasing in volume as well.

I stored the donor torque converter now in the transmission installed in my original tranny and tarped on a pallet out of doors. Prior to installation in my current transmission I drained it to ensure no moisture had accumulated in it and no moisture or particulate was found.

There are no fault indicator lights and OBDII scan shows no codes.

Ok, now for the questions.

Could storing the convertor installed in the old tranny have compromised some bearing inside it? Of course was not coupled to an engine to bear it's own weight.

I guess I'm wondering what is your take on the noise as described might be... could it be the torque converter? I'm thinking maby so since the noise always stops when the converter locks up in 4th gear. I took the vehicle to a Mr. Transmission shop that offered to trouble shoot it for free and they conclude that it can not be the converter stating that if it were it would make the noise in all gears regardless of lock-up. I did notice when driving to them at highway speeds that I felt a "seat of the pants" vibration in the drive train I don't recall being there before but I don't drive this car regularly as it is the wife's ride.

I read somewhere that the converter is locked in all gears but I don't think so as once at highway speed in 4th gear I can feel it lock and the RPM decrease about 100-200 RPM. What differs internally in the torque converter between lock-up and non-lock modes of operation? Is there a bearing not bearing weight or torque or is there some component that stops turning internally when the converter is locked?

I really need some comfort here because it's getting pricey to keep pulling this thing out and I don't want to buy a new (reman) converter only to thrown my money down the rat hole.

Steve

[plain OM]

What differs internally in the torque converter between lock-up and non-lock modes of operation?

The attached paper from Toyota is one of the best explanations I've seen of torque converter function, including lock-up. It's probably generic enough to apply to Subaru.

[steamin53]

Good write-up. Thanks. I wonder if there's such a thing as a partial lock in 4th prior to full lock up? That might explain the noise in 4th that goes away when the converter fully locks.

[plain OM]

I don't think there's an intentional partial lock, although the lock up isn't instantaneous -- it takes a bit of time for the pressure to build up on one side of the lock up clutch and to drain off from the other side.

The major difference between locked and not locked is that in the locked position the turbines of the TC are not actually functioning -- the input and output are mechanically connected and the various turbines are just turning along with everything else. When the TC unlocks, the power is transferred through the pressure of the ATF on the turbines. also, when shifting, the engine control module reduces engine torque momentarily, to take pressure off the transmission, so the TC is not under as much pressure -- I wonder if there could be something loose in the TC that "rattles" under these conditions.

Incidentally, was the donor transmission the same year (96)? There was a change in the TC in 97, and the 96 TC might not fit quite right.

[steamin53]

Plain OM you may be on to something. As I recall the donor trans may have been a 97 model which is at this time installed with the OEM 96 converter. However all the interchange data I find shows the converters for the 2.5L model Legacy Outback step roof to be the same from June 95 forward.

Can you detail the changes you refer to?

I agree it does act like something is loose in the converter causing noise when not locked up; but why not in 1st through 3rd gear? As I stated, except when shifting into 3rd as the torque load changes at the moment of the up-shift, the noise is only in 4th gear unlocked converter state.

One suggestion I've been give is that the band for the 4th gear is possible loose or the piston that actuates it may not be working correctly but it would seem that once the converter locks it would still make noise if that were the case.

[plain OM]

See attached. It's possible that the change between 96 and 97 applied only to certain models/versions, but I thought I'd mention it just in case.

[steamin53]

Well that's a simple thing to check. I doubt that I could have a mismatch because the torque converter would not seat if the splines were a mismatch.

The statement about the system replaced by the 97 change however would lead one to believe that the clutch in the converter could be the problem if indeed it is a mechanical lock up. However all the data I've seen about the transmission indicates that there are two servo controlled pistons in the valve body (I think) that control lock-up.

I'm still leaning toward the converter as the problem.

It is the simple and most basic logic as the converter is the variable in the current configuration versus the pre-repair configuration.

Geeze I wish I could find someone who could say yeah that sounds just like mine and here's what fixed it.

Stee

[nipper]

Lockup is either on or off. there is no inbetween. When the TC locks up there is no slip anywhere in the driveline from the engine to the tires.
Lockup is basically the TC having a giant clutch inside it.

Usually when a TC goes bad, it is the one way clutch that fails.
There really is no bad way to store a TC.

God I hate agreeing with a Transmission shop.

Riddle me this ...

(Humor me)

Shift the car manually on the next drive and listen for the noise..

When you hear the sound put the car into D3 and see if it goeas away.

With the usual warning "unless it is in my driveway I cant really tell" it sounds like your tranny is going. The seals in these never go bad unless there is another reason, and I think the bushing was the other reason. That bushing keeps other stuff aligned and can be the issue.

KUDOS to the tranny shops that did not try to sell you trannies, especially anything called Mr Transmission.

[steamin53]

Nipper thanks for coming to my rescue... AGAIN!

I know the answer to your question. The noise is present when in drive and the trans shifts into 3rd then is stops immediately until the trans shifts into 4th. In 4th the noise is constant until the converter locks at which time is immediately stops.

I will drive it starting in D3 position and post the results.

Do know if the converter only locks in 4th gear?

I must restate that with the donor converter in the trans after the bushing was replaced no noise was present. With the OEM converter installed the noise began. Many shops have said that the bushings tend to walk forward in these transaxles. That was the "presumed cause" of the bushing wear.

As a matter of fact it was a Mr. Transmission franchise that did the "2nd opinion". They offered that it could not be the converter because it didn't make the noise all the time and suggested perhaps loose band in the 4th gear range.

The local builder that replaced the bushing seems to disagree and thinks it may be the converter.

Steve

[nipper]

Converter locks anytim it feels like over i think 34mph. D3 keeps the car from going into 4th and lovking up the converter.

Of course they would balme the TC they can sell i big part and labor.

I generally think transmission shops are more evil then then Satan himself.

You know you can try a sooby dealer, as they really do not like doing transmission replacements as they don't usually stock them nor rebuild them. They also do not like giving customers heart attacks.