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96 Legacy Outback 4eat Trans Noise. Need Advice!


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8 replies to this topic

#1 steamin53

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Posted 28 January 2011 - 10:17 PM

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 torque converter seal fail in the donor tranny due to a worn bushing on the transmission input shaft. After replacement of the bushing and seal the seal still leaked. Removal of the torque converter again 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 I 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 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.

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.

Ok, now for the question. I'm uncertain as to whether storing the convertor installed in the old tranny may have compromised some bearing inside it. 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 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 RPM.

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

#2 grossgary

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Posted 29 January 2011 - 07:24 AM

sounds like it's possibly the teeth in one of the interlocking shafts between the trans/torque converter. something like this: the bad bushing caused some slop of some sort. it was enough to wear the seal which leaked, so seems possible that it could also have had enough slop to cause wear on a set of teeth engaging somewhere - in the torque converter or one of the shafts that engages it.

did you replace just the torque converter or any of the shafts with it?

you're originally talking about that bushing that slides around the mid-way point of the shaft going into the trans right? it's a circular graphite looking piece that's cut so it'll go around the shaft? if that's the one you're talking about - did you ever find the old one or is it's remnants somewhere in the trans?

obviously too late but for something as simple as torque bind, i would have just fixed the original trans. easy to fix and you don't even have to pull the trans to do it.

at this point i'd probably rather install the one known good trans you have. swap the rear extension housing and Duty C off the current trans into the old one to fix the torque bind and you got a good transmission. i would probably replace whatever the "new" trans needs though - rather than borrow anything torque converter related off the trans int he car. though i can understand not wanting a 200k trans in there but if it's in good shape?

#3 steamin53

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Posted 29 January 2011 - 09:47 AM

Thanks for your reply grossgary; it's all good advice.

The bushing that failed is the brass bushing in the front of the transaxle. I have considered installing the original trans and swapping the rear sections but of course there is uncertainty in it too as that tranny has been stored on a pallet out doors for a couple of years now.

I'm praying that it's a bearing in the torque converter and attempting to logically isolate to the converter. That would be my best case scenario.

What do you make of the fact that the noise stops once the converter locks?

Am I correct in my understanding of lock-up occuring in 4th gear only?

It seems to me that if that is the case then at lock-up converter bearings would be inactive and explain the noise stopping. I'm speculating, but it seems that a change in torque loading at 2nd to 3rd shift might also make the bearing talk. What's your take on these theories?

Steve

Edited by steamin53, 29 January 2011 - 09:59 AM.


#4 grossgary

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Posted 29 January 2011 - 03:32 PM

I found an older first generation 4EAT write up that says lock up does not occur in 1st, N, R, and P, but this is not a legacy.

brass bushing, i'm not familiar with what that is. can you describe where it was located?
i attached an exploded view from the FSM of the torque converter area if that helps.

did you replace the oil pump input shaft - the skinnier shaft that slides into the trans first that the TC slides over top of? i'm wondering if there's play between those two? granted it would seem like that should happen all the time unless it's jheavily related to load?

i skimmed the 96 factory service manual and found nothing. the troubleshooting section has all sorts of scenarios and their likely causes - but nothing about noises incurred with or without TC lock up.

Attached Files


Edited by grossgary, 29 January 2011 - 04:02 PM.


#5 steamin53

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Posted 29 January 2011 - 05:46 PM

The bushing that was replaced lies immediately behind the wiper seal for the torque converter shaft. It is referred to in one parts list at the CONVERTER HOUSING BUSHING and in another list as the BELL HOUSING TO CONVERTER HUB BUSHING. The bushing in the illustration you attached would lie immediately behind the seal which is called out as item 15.



I too find no reference anywhere to noise that goes away when the converter locks up.

Am I correct in the presumtion that the converter only locks in 4th gear?

Steve

Edited by steamin53, 29 January 2011 - 05:49 PM.


#6 steamin53

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Posted 29 January 2011 - 05:48 PM

Deleted as double post of same message/

#7 grossgary

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Posted 29 January 2011 - 09:36 PM

try some google searches maybe? i'm on dial up so i can't see what's out there.

but here's some later model 4EAT info as an example...again I couldn't down load it because of dial up:
http://www.spooledupracing.com/download/Manuals/FSM/Subaru/Impreza%2006/1-Training%20&%20General%20Tech.%20Ref.%20Books/4EAT%20(Automatic%20Transmissions).pdf

4EAT's haven't changed much in 20 years although around 98 or so they did have some changes. anything 88-97 4EAT related should be nearly identical in overview. even the newer models won't differ too much.

#8 steamin53

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Posted 29 January 2011 - 11:22 PM

Thanks for the information grossgary. I've read the information at that link previously. Unfortunately it just doesn't answer the questions. Are you aware that the first link you provided is of the transaxle and not the torque converter? I'm hoping to see what bearings might exist inside the torque converter.

Steve

#9 steamin53

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Posted 02 March 2011 - 09:15 PM

Problem Solved!

Just to close this as I hate threads that have no ending... happy or otherwise.

As it turns out two of the flex plate to converter bolts were not completely torqued down by the shop that did the trans R&R.

I torqued them down and presto noise and vibration gone.

(Mom always said "keep it simple stupid"!)

Steve




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