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Old 02-06-2003, 11:10 PM   #1
rexmobbin'
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Default rear diff oil change?

when should the oil in the rear differential be changed? how to do, and what kinda oil? thanks. its a 2003WRX if that matters
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Old 02-06-2003, 11:48 PM   #2
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change it when ever your feel like it. I changed mine at 10,000 with redling 75W 90. The regular stuff with the friction modifiers not he NS.
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Old 02-06-2003, 11:51 PM   #3
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With the friction modifiers? I dont think that is correct. The rear LSD is a sealed viscous unit right? If so then you should use the type without the friction modifiers.
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Old 02-07-2003, 01:12 AM   #4
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You don't have to change it until about 30-60K, but I chose to do it at 10K (after suffiecient break-in time) and changes to Redline 75w90 (not the 75w90NS which has friction modifiers). Really easy to do, and it'll cost you about $10 if you buy good fluid.

Rich
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Old 02-07-2003, 03:18 AM   #5
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Redline 75w90NS is the stuff to use. It does not have the friction modifiers. This is also what you want to use in the gearbox (5mt anyway).

The 75w90 HAS friction modifiers for limited slip units. We do NOT need these because Subaru LSDs are sealed. The STi mechanical LSD will probably require 75w90 with the modifiers.
Quote:
from www.redlineoil.com
75W90 GEAR OIL - recommended for most street driven and racing differentials. Excellent performance in conventional and limited-slip units. Also for limited-slip manual transaxles which require a 90 WT oil. Contains limited-slip friction modifiers.

75W90NS - recommended for manual transmissions and non-limited-slip transaxles that recommend 90 WT oils. Can be used in racing limited-slip units to increase lockup and reduce wheel spin. Street-driven rear-wheel drive cars should use regular Red Line 75W90 or 80W140.
Note : For the rear diff it probably doesn't make much difference which one you go with, but I think in the gearbox it's better to go without the friction modifiers so the synchros work better. I'd personally say to go with fewer additives if you don't need them... just more stuff to break down.
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Old 02-08-2003, 04:53 PM   #6
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Quote:
change it when ever your feel like it. I changed mine at 10,000 with redling 75W 90. The regular stuff with the friction modifiers not he NS
I concur with you're actions of replacing early reason being this should be done within early stages is because as the gears mesh together there is some shearing of the oil additionally abrasive wear is occuring within these units.

Changing fluid early removes these microscopic elements and adds longevity to the unit itself, even A/T should be fluid should be replaced at or around this time of 10k and install a very good synthetic fluid most imports utilize a screen mesh for the A/T filter thereby eliminating the need to drop the pan just the drain bolt, american cars employ a paper filter thats encased in a plastic body, dictating a pan drop and filter replacement. Only my 2 cents, yet it's worked well for me.
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Old 02-08-2003, 06:10 PM   #7
Peaty
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Old 02-08-2003, 06:29 PM   #8
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So having never taken my rear diff apart and never seeing a technical diagram I'm kind of in the dark about this.

Is the rear LSD a sealed type or not? If it's not sealed then yes you want the Redline 75w90 or just about any other synthetic (most all have the modifiers).

If the rear LSD is sealed then you don't need the modifiers and can go with the 75w90NS.

The center differential is a sealed unit and doesn't need them, and it helps the syncros to work if you use the 75w90ns.


This makes my head hurt.
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Old 02-08-2003, 11:31 PM   #9
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I changed mine at 1k with mobil1 75w-90 It was a terrible grey thick oil. Very opaque. Then I changed it again at 15k. Clear as a new. I would get the stock fluid out of there asap. It just looked wrong.
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Old 02-09-2003, 02:22 AM   #10
ShotgunTC88
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As far as I was told at my Subaru dealer they use 90wt in BOTH the M/T AND the Diff,

When I went in last week to get the Tranny topped off (they didnt fill it to full/ NewCar) They got the 90wt. out of a 30gal. VALVOLINE barrel!

SO, My guess it it is VALVOLINE 90wt.?


Shotgun
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Old 02-09-2003, 05:53 PM   #11
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In talking with Dave Granquist, Redline's technical advisor, he advised using regular 75W90 in the rear diff. He knew it was said to be a sealed unit, but had never taken one apart so wasn't positive. Regular 75W90 should be used in ALL applications UNLESS a special condition exsists to use the NS (ie transmissions requiring a GL5 fluid). He recommends regular 75W90 is all rear-end applications... sealed diff, open diff, non-sealed LSD, locking diffs... whatever. It certainly won't hurt the rear end having the friction modifiers.
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Old 02-09-2003, 06:48 PM   #12
CosmoTheCat
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Quote:
Originally posted by MrHorspwer
In talking with Dave Granquist, Redline's technical advisor, he advised using regular 75W90 in the rear diff. He knew it was said to be a sealed unit, but had never taken one apart so wasn't positive. Regular 75W90 should be used in ALL applications UNLESS a special condition exsists to use the NS (ie transmissions requiring a GL5 fluid). He recommends regular 75W90 is all rear-end applications... sealed diff, open diff, non-sealed LSD, locking diffs... whatever. It certainly won't hurt the rear end having the friction modifiers.
Good to know.
I stand corrected on the rear diff.
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Old 03-07-2003, 03:42 PM   #13
Ken C
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Default NS

Redline also recommends using the NS in the transmission, we believe.

Ken
Rally Performance
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Old 03-07-2003, 05:40 PM   #14
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Quote:
Originally posted by MrHorspwer
...............ALL applications UNLESS a special condition exsists to use the NS (ie transmissions requiring a GL5 fluid). ......................
uhhhh......but our manuel does call out for a GL5 type fluid....so doesn't that mean we should the NS?
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Old 03-09-2003, 04:50 PM   #15
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NS and non-NS oils are both GL-5 right?

I'm going to be using Motul Gear 300 synthetic oil when I change the transmission and rear transaxel fluids at 10k.
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Old 03-09-2003, 11:15 PM   #16
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I also changed mine at 1,000 (along w/ my engine oil) w/ 75W90 Mobil 1 for both rear diff/tranny (MT) and then every 10,000 after that. I too will be trying out Motul next change.

Big Sky
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Old 03-18-2003, 12:34 AM   #17
mrmcderm
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So what's the consensus here? Friction modifiers in the rear, no friction modifiers in the gearbox? So if I was using redline I would put NS up front, and 90w in the rear?


With all that said, I don't have a service manual handy, where is the drain plug on the 5MT, and what are the capacities on the 5MT and rear diff? I have to order some redline off the web and need to know how much to get.

thanks,
m
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Old 03-20-2003, 03:55 PM   #18
Frederf
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Friction modifiers should go in the gearbox to help the sychronizers. Actually, you'll probably want some mixture of Redline w/ friction modifiers and some Redline Shockproof.

The rear transaxle should take the slipperiest stuff they have, I think.
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Old 03-20-2003, 05:30 PM   #19
vile
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Quote:
Originally posted by mrmcderm
So what's the consensus here? Friction modifiers in the rear, no friction modifiers in the gearbox? So if I was using redline I would put NS up front, and 90w in the rear?


With all that said, I don't have a service manual handy, where is the drain plug on the 5MT, and what are the capacities on the 5MT and rear diff? I have to order some redline off the web and need to know how much to get.

thanks,
m
the consensus is that u will need friction modifier in the manuel tranny for the synchros and no friction modifier for the rear diff

the rear diff takes 0.8 qt. and manuel tranny takes ~3.7 qt
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Old 03-20-2003, 08:41 PM   #20
mrmcderm
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So let's say I don't rely on the synchros very much...i.e. I usually rev match and/or double clutch when I shift.

Would it be ok to put a mix of 90w (non-NS) and shockproof up front, and the same mix in the rear?

And even without friction modifiers, my synchros will still work, correct? They will just be a little bit more finicky?

The goal I'm trying to acheive here is maximum longitevity of my bearings and gears.
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Old 03-30-2003, 02:05 AM   #21
tracman
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I'M SO CONFUSED
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