Rear Differential!! how do i know is defective ?? - Subaru WRX Forum
 
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#1 Old 08-06-2009, 10:29 AM
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Rear Differential!! how do i know is defective ??

hey guys how can you tell if your rear differential is going bad or is bad already ?? also what year diffrentials bolt up to 2002 wrx with no modification ?? thanx tuners
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#2 Old 08-06-2009, 04:58 PM
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I suggest this..

Just up the rear of the car and support on Jack stands.
Pull off the skid plate that is located at the rear of drive shaft. Where it attached to the rear diff.
Pull out the (4) bolts that attach the drvie shaft to the rear diff.
Turn the yoke on the rear diff (where the drive shaft bolts up)
Watch tires. Make sure they both turn the same way. If one spins forward the other spins in revers your LSD is shot.

HOTE: Ron from Raw1perfromance.com informed me that in his experience a lot of 02 WRXs didn't come with rear LSD even some that were tagged as LSD were open diffs when we got them.. Could have been customers that swapped them or just not installed at factory, who knows..

There are plenty of diffs out there but make sure you match up the gear ratio. It's really not that hard to swapp the diff out yourself. Give Ron a call, he will hook you up with parts and help via phone.

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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#3 Old 08-06-2009, 09:22 PM
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Quote:
Originally Posted by LiL Shoaf View Post
I suggest this..

Just up the rear of the car and support on Jack stands.
Pull off the skid plate that is located at the rear of drive shaft. Where it attached to the rear diff.
Pull out the (4) bolts that attach the drvie shaft to the rear diff.
Turn the yoke on the rear diff (where the drive shaft bolts up)
Watch tires. Make sure they both turn the same way. If one spins forward the other spins in revers your LSD is shot.

HOTE: Ron from Raw1perfromance.com informed me that in his experience a lot of 02 WRXs didn't come with rear LSD even some that were tagged as LSD were open diffs when we got them.. Could have been customers that swapped them or just not installed at factory, who knows..

There are plenty of diffs out there but make sure you match up the gear ratio. It's really not that hard to swapp the diff out yourself. Give Ron a call, he will hook you up with parts and help via phone.

ok, i did something similar but i didnt take out any bolts.. the car was on a lift and while up there i turn one of the rear wheels, and the other one turn in the oppisite direction...what does that mean ??
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#4 Old 08-07-2009, 08:46 AM
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That boggles my mind. One tire spins forward, one spins backward, but the car still drives forward... wtf? I'd have to see how it works from the inside for my brain to fully comprehend the mechanical action.

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Last edited by man show; 08-07-2009 at 08:51 AM. Reason: ...and now I got it. Thank you Google video search.
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#5 Old 08-07-2009, 01:21 PM
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It means that your Rear diff is NOT an LSD.. If your car origionally came with an LSD rear differnetial (which if you remember earlier I stated that some didn't) it is bad.. The 2002 WRX came with a Vicious (SP?) rear LSD which works via pressure plates, or clutch disks depends on what you want to call them. The plates have friction between them and lock the rear wheels together until you over power that frictions.

Man show, any open diff will make one wheel spin forward and one back wards, it how the spider gears are configured to allow one wheel to spin faster then the other so the car will turn..

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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#6 Old 08-07-2009, 08:32 PM
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Quote:
Originally Posted by LiL Shoaf View Post
It means that your Rear diff is NOT an LSD.. If your car origionally came with an LSD rear differnetial (which if you remember earlier I stated that some didn't) it is bad.. The 2002 WRX came with a Vicious (SP?) rear LSD which works via pressure plates, or clutch disks depends on what you want to call them. The plates have friction between them and lock the rear wheels together until you over power that frictions.

Man show, any open diff will make one wheel spin forward and one back wards, it how the spider gears are configured to allow one wheel to spin faster then the other so the car will turn..
thank you very much dude !!! i guess i dont have lsd in the rear lol!
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#7 Old 08-09-2009, 07:53 AM
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I ran into the same thing, I blew out my OEM rear LSD and had to replace it. It cost me about $900 for a Kazza unit which is a little noisie (you hear it clunking when you turn) but it works fine.. PPG has a nice unit but it's a little more money, if your interested in that call Andrew at andrewtech automotive.. As for the install, Andrew can walk you through it as well. I did mine myself.. Just remember that the Ring gear bolts are LEFT Hand thread so it's not rightie - tightie / Leftie - Loosie. LOL.

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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#8 Old 08-09-2009, 02:59 PM
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Yeah, my rear LSD does that if i try to turn it hard while parking or if its on "lock" on my DCCD.
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#9 Old 08-09-2009, 07:35 PM
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The PPG setup is suposed to be quiet and strong. I can not atest to this as I only have the Front PPG LSD as the rear was not released in time for my build.. I would like to upgrade at some point however..

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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#10 Old 08-09-2009, 07:47 PM
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I'm bored so I figured I would "Share" a little about differentials..

http://i111.photobucket.com/albums/n...0Junk/Open.jpg

Above is an "OPEN" differential. You can see in the left side of the picture the "Ring Gear" and "Spider Gears". This type of differential creates the famous "One wheel Peal" as the spider gears allow the axels to spin at different RPMS. the spider gears rotate themselves and the entire assembly rotates inside the housing.. It's hard for me to explain how this works with out showing it physically.. Hopefull someone else can expand on it better then I..

http://i111.photobucket.com/albums/n...aton20Posi.jpg


above is "Form" of LSD. There are several types of LSD units. The factory 02 style LSD is a friction plate style. (NOT illustrated). Inside the ceter section instead of spider gears there are several friction plates that press against each other. These plates lock the axles together but will slip on each other when the resistance on the wheels over powers the friction between the plates. This is IMPORTANT becuase it allows the outside wheel to spin faster around bends allowing the car to turn sharper. When both wheels are fully locked together (Like if you welded the spider gears like the old timers do) both wheels always spin at the same rpm which will make one wheel litterally skip and lose traction when turning sharply thus increasing the cars turning radius..

The pictured LSD uses a clutch system which is very similar in theory...

below are what our LSDs look like..
http://i111.photobucket.com/albums/n...0diff20002.jpg
http://i111.photobucket.com/albums/n...0diff20001.jpg

As you can see in this picture the Front Differential in the 02 is an OPEN style.
http://i111.photobucket.com/albums/n...u/P7140428.jpg

Ohh yea, once you fix it you can do this..
http://i111.photobucket.com/albums/n...76_76_full.jpg

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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