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So I've had a rear main shaft bearing failure on my 2004 Impreza TS with 5MT.

I knew one of the main shaft bearings failed because the car sounded like a rally car in the first 4 gears, mind you not that loud, but gear whine was present.

 

I picked up a used tranny out of an older car to hold me over while I fix this one and keep it as a backup (Unknown mileage on used tranny, not the first car it was in either, was CHEAP)

 

Now, I've got my tranny torn apart, I need at MINIMUM a rear main shaft bearing 806225170.

I've noticed the parts diagrams list one for turbo and one for non-turbo.

The turbo one appears to be a dual tapered roller setup.

 

Can that setup fit in my cases? Is it an outer race that can retro-fit? Is it an upgrade?

Also, the secondary shaft, how often do those massive bearings fail? Should I definitely replace those ones too? That shaft looks like a real pain in the rump roast to replace those bearings.

I have 280k KM on this tranny, and want to replace both main shaft bearings, and any of the needle bearings the gears run on if they're looking bad. As well as the front diff bearings (They look well used).

 

Should I replace the centre diff bearings too? Or leave them if they're not making any noise?

 

And obviously will be replacing all the seals in the case while it's open.

 

Good news is, all the synchro's and gears look perfect, once the noise started, the car had only about another 100km on it and it was getting progressively worse over that time.

 

The bearing with my thumb on it is the one in question, it's cooked, wobbly, loud, crunchy, 3mm play lengthwise...

post-66974-0-14861300-1495730292_thumb.jpg

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Like GD said. Replace the center diff while you have it apart. I would also replace any bearings on the transfer shafts that feel worn or make excessive noise.

 

Haven't ever seen or heard of any bearings on the secondary going bad unless the trans has damage elsewhere. Those can be left alone as well as the needle bearings on the input shaft.

 

Pretty sure the STI bearing won't fit, but I'm not 100% on that. The STI 6 speed trans uses a pressure lubrication system with a pump that's driven by the main shaft so pretty much everything is different on those.

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I think he means the 5 speed turbo trans tapered roller bearings. I'm fairly sure you could swap them in, yes. I have not done it. It's usually unnecessary because by the time the trans fails for a second time the car would have so many miles on it that it wouldn't be worth the investment. Usually those transfer section bearings only fail when the center diff grenades into them.

 

GD 

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If the center diff has lasted 280k KM, why would I replace the entire unit? I mean if they fail "regularly" and mine lasted this long....? I've seen the bearings fail (external to the unit) and be replaced without further issue.

 

This isn't a show car, it's a "family" car... it doesn't get driven hard, and it's all stock aside from the radio which is only because the OEM one died.

We bought the car for $2500... 3 years ago... put a rad in it ($15 from Wreckers), starter ($160), mystery tranny from a 99-01 Impreza ($200 came with a rear diff, didn't install), brakes were done once.. so far it's been a pretty cheap car to own.

 

Is it worth mentioning that the "thrust plate" is completely mint? Shows no marks on it at all, I see no reason to replace it, it holds the race in the case perfectly as is.

 

This tranny is hilariously simple looking inside, makes some of the dirt bike motors I've been in look complex in comparison. Though I'm sure some of the "Enthusiast" type guys would be minorly jealous of a bike transmission which is a small sequential dog box :)

 

Thanks for the help guys.

 

EDIT: Did some reading, looks like the C Clip comes off the centre diffs... does mine look like the new version or old one?

 

 

post-66974-0-27646700-1495760886_thumb.jpg

Edited by Borgschulze
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The center diffs do not go bad in a way which renders the car undrivable. It creates a torque bind situation where it starts to feel like a 4x4 in tight turns, and the 5spd viscous centers will ALL do it eventually. Yours almost certianly does but you probably don't notice it. Likely has been bad for a while

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I would look into just getting a complete JDM transmission. There are several Canadian importers online that have complete transmissions with 40-50k miles for less than the cost of a new center diff. I got a dual-range even shipped from Canada to South Carolina for about 700, and the shipping was as much as the cost of the trans!

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The center diffs do not go bad in a way which renders the car undrivable. It creates a torque bind situation where it starts to feel like a 4x4 in tight turns, and the 5spd viscous centers will ALL do it eventually. Yours almost certianly does but you probably don't notice it. Likely has been bad for a while

My center diff does not torque bind, I can basically idle at full lock and it doesn't make any noise, neither does the one in the used mystery tranny I bought.

 

I did test it before pulling the tranny, because at first I suspected center diff was bad.

 

 

I would look into just getting a complete JDM transmission. There are several Canadian importers online that have complete transmissions with 40-50k miles for less than the cost of a new center diff. I got a dual-range even shipped from Canada to South Carolina for about 700, and the shipping was as much as the cost of the trans!

 

Can you name some places? Had I found a place with a $350 JDM tranny with low KMs, I would have bought that over mystery $200 tranny for sure.

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The center diffs do fail. They have a tendency for the pinion gears to seize up or their thrust washers to disintegrate and end up being sucked into the transfer gear train.

 

They can cause binding, OR they can strip some spines from some of the plates in the VC and end up not being able to turn the front wheels at all. Seen both failures many times.

 

GD

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