Welcome to the North American Subaru Impreza Owners Club Sunday November 23, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC General > Motorsports

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 01-06-2006, 05:33 PM   #1
makofoto
Scooby Guru
 
Member#: 25243
Join Date: Sep 2002
Chapter/Region: SCIC
Location: South Pasadena, CA
Vehicle:
2006 Legacy Outback
Blue

Default Rear Dif Out? How to Tell?

I was going to finally pick up my WRX after Steve @ Suby Specialties rebuilt my 5 spd and pulled my SM mods so I could run STX.

When he test drove it, the front inside wheel spun very easily, now that I don't have a front LSD. But he said it spun way to easily ... as if my oem rear LSD was gone. It's like I now have a 290 hp FWD car.

I believe him. It's not like the busiest Suby Mechanic around is trying to drum up more business. I bring him a lot of new business and he gives me discounts.

But HOW does one know the rear dif is gone?

Since we are allowed to have a rear LSD in STX ... can one replace it with a mechanical LSD or must one stay with the oem viscious coupling version?
* Registered users of the site do not see these ads.
makofoto is offline   Reply With Quote
Old 01-06-2006, 05:44 PM   #2
javid
Scooby Specialist
 
Member#: 54304
Join Date: Feb 2004
Chapter/Region: South East
Location: Atlanta
Vehicle:
04 STi
TopSpeed-dAng!

Default

Couldn't the problem also be the center diff?

Sorry, I have no potential solutions. Well, except in my STi when you try to exit too hard or too quickly the rear end makes all kind of racket. I assume this is the rear diff and wheel hop due to the inside wheel being unloaded.
javid is offline   Reply With Quote
Old 01-06-2006, 05:50 PM   #3
tacomaprime
Scooby Specialist
 
Member#: 70572
Join Date: Sep 2004
Chapter/Region: MWSOC
Location: Cybertron
Vehicle:
2005 Tacoma
Blue

Default

put the car up on a lift, turn it on, press slightly on gas, see if rear wheels spin?
tacomaprime is offline   Reply With Quote
Old 01-06-2006, 05:51 PM   #4
afpdl
Scooby Guru
 
Member#: 26361
Join Date: Oct 2002
Chapter/Region: TXIC
Location: Sugar Land (Houston), Tx
Vehicle:
My shenanigans are
cheeky and fun

Default

How does the inside front wheel spin relate to a broken rear diff?
afpdl is offline   Reply With Quote
Old 01-06-2006, 06:21 PM   #5
javid
Scooby Specialist
 
Member#: 54304
Join Date: Feb 2004
Chapter/Region: South East
Location: Atlanta
Vehicle:
04 STi
TopSpeed-dAng!

Default

with an open center if your rear diff is completely shot (no shaft torque gets to either axles) then all power goes to the front, aka twice as much as normal and so it would be twice as easy to spin the inside front....
javid is offline   Reply With Quote
Old 01-06-2006, 06:27 PM   #6
javid
Scooby Specialist
 
Member#: 54304
Join Date: Feb 2004
Chapter/Region: South East
Location: Atlanta
Vehicle:
04 STi
TopSpeed-dAng!

Default

Quote:
Originally Posted by ADIDAS
put the car up on a lift, turn it on, press slightly on gas, see if rear wheels spin?

Maybe use some e-brake action during this test too? You can adjust the pressure of the shoes on the right and left differently, which may explain a little more.
javid is offline   Reply With Quote
Old 01-06-2006, 07:43 PM   #7
skuttledude
Scooby Specialist
 
Member#: 738
Join Date: Jan 2000
Chapter/Region: MWSOC
Location: Southern Ohio USA
Vehicle:
2008 Lexus IS-F
Ducati Monster 800

Default

rev to 6,000rpm's, drop clutch, see which tires spin

seriously, I like the put the car on lift idea
skuttledude is offline   Reply With Quote
Old 01-06-2006, 10:25 PM   #8
Warp3
NASIOC Supporter
 
Member#: 161
Join Date: Aug 1999
Chapter/Region: South East
Location: WNC
Vehicle:
06 WRX TR (SGM)
89 MR2 (Ice Blue)

Default

Quote:
Originally Posted by makofoto
Since we are allowed to have a rear LSD in STX ... can one replace it with a mechanical LSD or must one stay with the oem viscious coupling version?
AWD cars have to use the factory diffs in Street Touring unless they came from the factory with NO LSDs (including the center diff) then they can add one. So, sorry...factory viscous only for the WRX.

Shane
Warp3 is offline   Reply With Quote
Old 01-06-2006, 10:32 PM   #9
cowapult
Scooby Specialist
 
Member#: 25324
Join Date: Sep 2002
Chapter/Region: MAIC
Location: London, UK (formerly Wash DC)
Vehicle:
00 2.5RSwhite-sold
91 Legacy Turbo Red

Default

a) I don't see how this could have anything to do with the viscous rear coupling. He must have said (or meant) center diff. If anything, a shot rear vicous would do the opposite of what you're describing. Javid does point out one way that a rear diff would cause this problem, if it had completely grenaded and lost all its teeth, but I think you would notice if your rear diff had detonated that bad.

b) A blown viscous center diff would cause these symptoms, but it's not nearly as bad as having a FWD car. With an open diff, you will still get exactly 50% of the torque to the rear. You'll tend to spin the front a bit sooner than the back because they have less weight on them. That is, unless "bad diff" means you're actually missing teeth in the center. That's a whole different story.

c) I think Javid pointed out the only way to test it. Put the car on a lift, put it in first and let it idle. See if all the wheels turn. If all 4 spin, then none of your diffs grenaded. If just the front spins, then something is completely busted and disconnected in your rear diff or drive shaft

Assuming all 4 spin, then get the engine going faster and apply the e-brake. Your rear wheels should obviously slow down. Listen if the engine slows at all, watch if the front wheels slow at all. If the engine keeps going the same speed and front wheels speed up - that means your center diff is working but it's open, not viscous. By contrast, if the front wheels and the engine slow, then your center diff is doing its viscous job and all this fuss is just you noticing that you took out your front LSD.

Last edited by cowapult; 01-06-2006 at 10:42 PM.
cowapult is offline   Reply With Quote
Old 01-07-2006, 02:17 AM   #10
makofoto
Scooby Guru
 
Member#: 25243
Join Date: Sep 2002
Chapter/Region: SCIC
Location: South Pasadena, CA
Vehicle:
2006 Legacy Outback
Blue

Default

I haven't had a chance to drive or see the car myself, and won't be able to until next week now. Steve is a MASTER Suby Mechanic with his own garage ... that gets rave reviews.

The Center Dif is BRAND new. The "old" one was blown open when I stripped 2nd gear.

The Center Dif and Rear Dif are viscous coupling ... no teeth.

Found a brand new oem rear dif for $200.
makofoto is offline   Reply With Quote
Old 01-07-2006, 04:21 PM   #11
cowapult
Scooby Specialist
 
Member#: 25324
Join Date: Sep 2002
Chapter/Region: MAIC
Location: London, UK (formerly Wash DC)
Vehicle:
00 2.5RSwhite-sold
91 Legacy Turbo Red

Default

Oh, they have teeth alright
cowapult is offline   Reply With Quote
Old 01-07-2006, 06:34 PM   #12
RebelINS
Scooby Specialist
 
Member#: 2953
Join Date: Nov 2000
Chapter/Region: MWSOC
Location: Rochester, MI, USA
Vehicle:
2000 Impreza 2.5RS
2005 Impreza WRX STi

Default

I believe cowapult is talking about ring and pinion teeth.

-Wes
RebelINS is offline   Reply With Quote
Old 01-09-2006, 11:08 AM   #13
ratt_finkel
Scooby Specialist
 
Member#: 46218
Join Date: Oct 2003
Chapter/Region: TXIC
Location: Dallas, Tejas
Vehicle:
06 EVO 9
Silver

Default

Quote:
Originally Posted by makofoto
IWhen he test drove it, the front inside wheel spun very easily, now that I don't have a front LSD. But he said it spun way to easily ... as if my oem rear LSD was gone. It's like I now have a 290 hp FWD car.
How do you think us Evo owners feel?
ratt_finkel is offline   Reply With Quote
Old 01-09-2006, 11:32 AM   #14
leecea
Scooby Guru
 
Member#: 37359
Join Date: May 2003
Vehicle:
2003 WRX

Default

You probably have a big front sway bar - I think that will help make the inside front spin.
leecea is offline   Reply With Quote
Old 01-09-2006, 11:39 AM   #15
ratt_finkel
Scooby Specialist
 
Member#: 46218
Join Date: Oct 2003
Chapter/Region: TXIC
Location: Dallas, Tejas
Vehicle:
06 EVO 9
Silver

Default

Quote:
Originally Posted by leecea
You probably have a big front sway bar - I think that will help make the inside front spin.
Indeed it will. Something I noticed after slapping the FSB on my Suby.
ratt_finkel is offline   Reply With Quote
Old 01-09-2006, 01:29 PM   #16
makofoto
Scooby Guru
 
Member#: 25243
Join Date: Sep 2002
Chapter/Region: SCIC
Location: South Pasadena, CA
Vehicle:
2006 Legacy Outback
Blue

Default



Doesn't have a big front sway bar, only a Hotchkis hollow = 22 mm
makofoto is offline   Reply With Quote
Old 01-09-2006, 03:08 PM   #17
solo-x
Scooby Specialist
 
Member#: 37624
Join Date: May 2003
Chapter/Region: NESIC
Location: Doesn't drive a scooby....
Default

jack up the rear of the car. put the tranny in gear, then while someone holds one wheel, try to turn the other. there will be nearly no resistance at all if the diff is "blown".

to blow up a viscous diff it would take a LOT of work.

fyi, there is a lot of misunderstanding/misinformation of how diffs work being tossed around in here. i'd try to help straighten it out, but it's such a mess already it would be difficult to clarify everything without a page long post. i'm pretty confident that the rear diff in mako's car is fine. i'd be looking at center diff possibly. if the rear diff was blown, the inside rear would spin to high heaven. you KNOW it was blown. saying the rear diff is blown and causing massive inside front wheelspin is suspect.

nate
solo-x is offline   Reply With Quote
Old 01-11-2006, 11:40 PM   #18
makofoto
Scooby Guru
 
Member#: 25243
Join Date: Sep 2002
Chapter/Region: SCIC
Location: South Pasadena, CA
Vehicle:
2006 Legacy Outback
Blue

Default

You're correct ... mine is OK.

There are three tests according to Subaru:

If the fluid is really burnt ... it should vent through a "blow" hole at the top of the differential.

Second, with the rear wheels off of the ground turn one wheel by hand while holding the other one stationary. It will turn fairly easy at first, but after a couple of seconds it should noticeable stiffen. Apparently it takes a couple of moments for the fluid to start being forced through some apertures.

Third, with the drive shaft locked in position, turning one rear wheel should make the other wheel turn in the same direction if the rear LSD is OK. If the rear LSD is really out, the other wheel will either not turn or turn in the other direction. I think I got that right.
makofoto is offline   Reply With Quote
Old 01-12-2006, 12:25 AM   #19
kcscoob
Scooby Specialist
 
Member#: 31222
Join Date: Dec 2002
Chapter/Region: MWSOC
Location: Overland Park, KS
Vehicle:
2005 Legacy GT wagon
6 speed, BNR 18G, E85

Default Axle shaft?

This is likely not the issue but I had an axle shaft come out of the rear end of my WRX and my car acted like it was a front wheel drive for a while and then it would barely go at all because of all the slippage.It was a while before it was diagnosed because the shaft was only out about 3/8 of an inch and everything looked normal from first glance. The center diff needs resistance from both the front and rear diffs to work. You might check to see if both shafts are completely in before you tear things apart.
kcscoob is offline   Reply With Quote
Old 01-12-2006, 01:17 AM   #20
Student Driver
Scooby Specialist
 
Member#: 65161
Join Date: Jun 2004
Chapter/Region: SWIC
Location: AZ
Vehicle:
2002 2.5RS, AW
I can taste teh suck

Default

Honestly, it seems like there's a longer delay between front wheel spin and rear diff lock than I would think. Ever since I went Cobb Stg 1, I would get a little front spin during certain turns on my way to work (if I felt a little punchy anyway ). Now, at Stg 2 with a 22mm front bar, I can get that front inside wheel to light up briefly (less than half a second I think) and then "wooshhhh" when the rear hooks up. On the RS, both the inside wheels would just spin in similar situations (albeit a little wet so it could actually turn the wheels).
Student Driver is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
how to tell if i have rear lsd yeos Transmission (AT/MT) & Driveline 4 02-23-2009 03:25 AM
R180 rear diff: How to tell if its plated Ben v5 Transmission (AT/MT) & Driveline 2 05-04-2008 07:44 AM
How to tell size of rear sway bar Tom MY03 Brakes, Steering & Suspension 4 05-11-2005 07:52 PM
How to tell Stock Front Springs from Rears? MY99 2.5GT Brakes, Steering & Suspension 7 04-19-2002 09:54 AM
How to tell how much brakes left? Penphoe Brakes, Steering & Suspension 3 06-19-2001 03:08 AM


All times are GMT -4. The time now is 09:18 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.