4eat tail section rebuild without removing transmission - Subaru Outback - Subaru Outback Forums
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post #1 of 26 (permalink) Old 09-18-2010, 09:45 AM Thread Starter
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4eat tail section rebuild without removing transmission

So i broke something, lost rear wheel power and wasn't convinced it was a speed sensor. I picked up a bad but FREE used transmission that should still have a good extention/tail housing, clutch pack and solenoids.

1) First get the vehicle as high as possible, you will be under it the whole time. I have ramps in my garage that i drive up onto and lifts whole car the about 18 inches under the tires. 24 would have been nicer.



2) while my exhaust cooled done i drained the transmission fluid, and disconnected 02 sensors.

3) drop the exhaust, mine is all one big welded piece so i unbolt it at the heads, undo the rubber mounts and the entire system slides out of the way.

4) time to situate the rear driveshaft, I unbolted the center carrier bearing, and removed the rear u-joint shield hoping to get enough drop to pull driveshaft out of transmission without unbolting the u-joints, no such luck, it had to wait untill i removed transmission cross member.



5) i removed the 4 nuts holding transmission mounts to cross member, i then slid a heavy board from ramp to ramp to place a jack on to support transmission while i unbolt the cross member.

6) now with the cross member out of the way i used the jack to lower the transmission just enough to slide the drive shaft the rest of the way out and the used a bungee to hold it out of the way, then removed the transmission mount from cover mostly just for more room



7) remove the 10mm bolt holding in the speed sensor, place sensor out of way and remove rear cover and find your surprise. mine was that the stamped gear that drives the clutch pack had broken off the output shaft.




8) replace necessary parts clean all the gasket surfaces and prepare to reassemble.
when recombining the clutch pack and basket i found it easiest to carefully slide basket into the clutches, it took a while and was pretty frustrating trying to get all those clutch discs lined up so it all went back together, but with some pressure and twisting motions it all fell in place.

I got all my parts out of this donor transmission



9) i put output shaft and clutch pack back into transmission as one piece and then slid cover back over it, careful to tuck the solenoid plug into the transmission. i didn't and crushed my plug when i put cover back on and that sucked to fix.




10) finish reassembly.

The most time consuming part was cleaning gaskets and then another half hour replacing solenoid plug so in all it took me about 3 hours, I used about 6 quarts of dex III but have to do i final level check yet, but 6 came out so i put six back in. the fluid change seemed to help the shifting, the clutches grab sooner than my old worn out set so it all seems to have gone pretty well.
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post #2 of 26 (permalink) Old 09-19-2010, 09:10 AM
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Thanks for posting this DIY thread. In the past there have been requests for "instructions" on dropping the tail section. The excellent pics showing the interior with the clutch pack and duty solenoid, along with the notes, will be a great help.

Quote:
the stamped gear that drives the clutch pack had broken off the output shaft
Was the hub (the "stamped gear") originally welded to the reduction gear (photo above) or was it only pressed on?

Sort of suggests that if the transfer clutch locks up, then in addition to the common wheel hop/skip and hesitation symptoms of "torque bind", the transfer clutch hubs might be vulnerable. Or, perhaps the hub was breaking loose and that caused the binding, at least until the hub broke free.

Ref: my awd just quit....i think )
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post #3 of 26 (permalink) Old 09-20-2010, 03:45 PM Thread Starter
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The metal on the stamped gear itself tore away where it was weakest at the three indents. As far as being one with the reduction gear or a seperate piece, I will have check and photo later.

edit:

it turns out the hub/stamped gear and reduction gear are supposed one piece. the reduction gear is cast and the hub is steel but they are welded together and share the same cast splines. they are held onto the output shaft by a c-clip. the hub could be replaced with the reduction gear as easy as replacing the duty c by removing the clip and pulling the gear off the shaft. a couple good smacks on a hard surface and the gears and bearing came off the shaft.




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post #4 of 26 (permalink) Old 09-20-2010, 07:55 PM
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The photos of the hub, especially the second-to-last above, show deep grooves where the driven clutch plates bear against the outer "teeth" of the hub. Those grooves can cause the plates to bind by not allowing them to move forward and backwards along the teeth.

That hub is what transfers the tranny output shaft power to the driven clutch plates, and through the clutch to the rear propeller shaft and wheels. The welded joint between the hub and reduction gear can therefore be subjected to a lot of stress, all the more so if the clutch plates are binding.

This is a great thread. Again, my personal thanks for posting this.

Edit: How many miles on the transmission?

Last edited by plain OM; 09-20-2010 at 08:00 PM. Reason: add mileage question
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post #5 of 26 (permalink) Old 09-20-2010, 08:19 PM Thread Starter
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i thought i felt something in the drivetrain acting up the last couple months. this transmission has 162k miles and saw a lot of offroad use and a lot of heavy loads, some of those loads close to 2000 pounds in the cargo area. i used this vehicle primary to retrieve rocks and boulders from out of the woods for building ponds and other landscaping. the car has paid for itself 10 times over

http://picasaweb.google.com/11663887...eat=directlink
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post #6 of 26 (permalink) Old 09-21-2010, 08:59 AM
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That is some pretty gnarly grooving.

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post #7 of 26 (permalink) Old 09-21-2010, 09:00 AM
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I just looked at what you do with that poor subie- you're a very very bad man!


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post #8 of 26 (permalink) Old 11-02-2010, 08:04 PM Thread Starter
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i've been better to subie lately, getting some new 215/75/15 firestone destinations a/t's for her next week. the 08 12k mile forester suspension has been a real nice addition
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post #9 of 26 (permalink) Old 11-19-2011, 02:24 PM
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To kick a dead thread...

Quote:
Originally Posted by no694terry View Post
...what surprises me is the difference in the depth of this super deep indentations: This suggests difference of clutch plates loading!
In similar motorcycle clutches I have never seen this.
Ideas?
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post #10 of 26 (permalink) Old 11-19-2011, 06:26 PM
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Thanks for reviving this thread.
I have not yet seen a hub with such deep grooves.

My take on the differences in groove depth:
Looks like a slight hydraulic pressure drop across the plates.
The rear plates are able to grab quicker and have less of a chance to "slam" into the hub.
But* front plates receive the power first from the transmission, & the pressure from engagement comes from the rear.
Looks like the deepest groove takes the most shock & power from engagement.
It probably exacerbates itself once a small groove has developed.

Didn't see a photo, but were there grooves in the outer basket as well?

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