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Drive train issue


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12 replies to this topic

#1 lichen

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Posted 30 August 2017 - 01:30 AM

Hey guys, thank you for all your helpful tips in the past. And now I have another question.

My '95 Legacy has a rear diff and drive shafts just like my '98 Outback, but it's only front-wheel drive. There is a fuse passenger side firewall that links a 'fwd' light in the instrument cluster. Light goes out when fuse is removed.

Outback has the same fusible link, but when I plug in a fuse, no 'fwd' light appears.

The Outback has some kind of binding issue in the drivetrain. The rear diff was ruined because I put too small a donut tire on driver side rear. I replaced rear diff, and it was fine for a week, then the passenger side rear axle slipped out while wife was driving. It slipped back in for me but when I drove it away, within 10 miles I knew I had another problem on my hands. Felt like a 4x4 truck locked in on dry pavement and turning tight circles, sort of..

2 things: I bought new tires for it, but they're different brands. 2 are the same, the other 2 are different from each other and from the two that are the same. I ran a tape round the circumference of each and discovered a 3/4" difference between smallest and largest. If my calcs are right, this amounts to roughly 1/2 of 1% of diameter difference. Might that have caused drive train gear damage?

I took the differential out of a standard-tranny '98 Outback to replace the differential in the auto-tranny 98' Outback. I checked the gear ratio with chalk marks on wheels and driveline.

The axles are the type that don't have spring pins to pin them in place. You seat them, and that's it. I do not understand how the one slipped out.

Main question: Is there a way to disable the AWD on this (automatic) Outback so only the front wheels are drivewheels? To essentially make it a fwd car rather than awd?

#2 Mike104

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Posted 30 August 2017 - 07:28 AM

According to Subaru all four tires must be within 1/4 inch of circumference.  All four tires should be same brand, same size.  

 

You likely damaged the clutch pack in the tail end of your transmission (auto) or Viscous Clutch (Manual transmission).  You have torque bind.

 

The fuse should not be in place in either car to get AWD.  In your owners manual it tells you that if you have to put on the small spare tire to put it on a rear wheel (move the removed wheel to the front if needed) and put the FWD fuse in the holder under the hood.  This energizes the Duty C solenoid to put your car in FWD.

 

The intent is that the FWD fuse be put in only when needed.



#3 1 Lucky Texan

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Posted 30 August 2017 - 08:23 AM

^^^ what he said

 

when Subaru AWD is abused, the weakest link suffers - that is usually the center differential function (actually, wet clutch pack in the automatic transmissions) not the rear diff (though, ANYTHING can break of course)

 

you need to start with all-same tires if possible, but, if you already KNOW you have torque bind, you can use the FWD fuse foreever if you want and use any size tires.

 

If you still experience torque bind with the fuse in place, there is either a mechanical problem in the tailshaft area of the trans, or possibily an electrical problem with the Duty C Solenoid or it's control wiring.



#4 Gloyale

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Posted 30 August 2017 - 10:24 AM

I'm confused.  Are we talking about 2 cars or 3 here.  first you say 95 legacy, then you talk about 2 different 98 outbacks.  none of them should have ruined anything by having a donut spare on the rear.  No limited slip in the rear.  Especially if you put the FWD fuse in.  Manual cars do not have the FWD fuse option.

 

You must have counted your chalk marks wrong.  If you put a Manual rear diff in the auto you've got mismatched gear ratios.

 

Manual 4.11, Auto 4.44

 

that will definately cause binding.



#5 lichen

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Posted 30 August 2017 - 04:20 PM

Thanks for the info, guys. You've already said a lot I didn't know.

 

I was using my smartphone to make that post, and it's tedious. Now I'm on a computer keyboard, so it's a lot better.

 

I was comparing the three cars because I'm just trying to figure things out.

 

Now: If the ratios are different between auto and manual in the rear differentials, then that's why I have gear binding. I don't know how much damage there might be in the transmission, but my main question is this: 

 

Is there a way I can permanently disable the rear differential and make it a front wheel drive car? For example, can I simply remove the rear drive shaft?

 

My secondary question is this:

 

Why is my 1995 L wagon fwd only when it features a rear differential?

 

Interesting side note: I replaced all the struts/springs on the '95 L (which came equipped with 13" wheels), with the suspension components off the Outback, so I could put 15" wheels on it. Everything bolted straight in, and it looks like an Outback now.



#6 Gloyale

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Posted 30 August 2017 - 09:52 PM

Why is my 1995 L wagon fwd only when it features a rear differential?

 

Because the fuse is in.  It's a fueture for using donut spare on rear to disable rear drive.  

 

Normal use, remove the fuse and it will be 4wd.



#7 lichen

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Posted 30 August 2017 - 10:12 PM

Is it okay to remove the rear driveline on the torque-bound Outback?

#8 Gloyale

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Posted 31 August 2017 - 02:02 PM

Is it okay to remove the rear driveline on the torque-bound Outback?

 

automatic yes.  (leave the front portion between trans and carrier, remove the rear half)

 

Manual no.  The center diff will spin......you might get a tiny bit of drive through the VLSD before it wears out.....but it's not gonna drive well or for long.



#9 lichen

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Posted 31 August 2017 - 02:06 PM

Took out rear driveline, seems to drive okay now. Thanks, guys!

#10 lichen

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Posted 10 September 2017 - 04:07 PM

Hi, guys, I am trying to find out if I can take the rear differential out of my 2000 Forester (auto) and install it in the 1997 Outback (also auto).



#11 lichen

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Posted 10 September 2017 - 04:51 PM

Bump



#12 Gloyale

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Posted 10 September 2017 - 06:46 PM

Hi, guys, I am trying to find out if I can take the rear differential out of my 2000 Forester (auto) and install it in the 1997 Outback (also auto).

yes but the input flange may be different. 2000 larger.

 

swap those and should work.



#13 lichen

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Posted 13 September 2017 - 05:14 PM

Thanks, got the swap done, and looks like everything is okay. Swap was easy, bolted right in. Took the covers off, counted the gear teeth, everything's a match.






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