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Best Gear Oil for Man. Transmission/ Differentials in 98 OB?


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13 replies to this topic

#1 Equalizer

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Posted 04 May 2005 - 04:36 PM

Car: 98 Legacy Outback, 5 speed Manual Tranny.

Situation:
I plan to change my ball joints this week, time permitting. Shudder/vibration in front end. The car has 115,000mi. on it. Unrelated to the joints: I bought it used, so the Gear lube has probably never been replaced. Since I'll have the car on stands changing the joints, thought it'd be a good time to kill another bird, or two while I'm at it, and change the Manual trans. oil, (not to be confused with trans fats, or triglicerides :) ). Also might be able to change the differential oils while I'm at it too. I've had some trouble shifting when starting out in the mornings through the winter, so I'm considering full synthetic.

Questions:
1. What is the safest and best viscosity/brand/type to replace in the Manual gear box, and in both differentials?
2. What do you think about synthetic, as oppossed to dino for these applications, and why?
3. Any tricks to changing these that aren't described in the Haynes Manual?
4. Lastly, Do you recommend any special additives that might help keep the gaskets plyable, or be beneficial?

#2 rizzo

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Posted 04 May 2005 - 06:06 PM

Car: 98 Legacy Outback, 5 speed Manual Tranny.

Situation:
I plan to change my ball joints this week, time permitting. Shudder/vibration in front end. The car has 115,000mi. on it. Unrelated to the joints: I bought it used, so the Gear lube has probably never been replaced. Since I'll have the car on stands changing the joints, thought it'd be a good time to kill another bird, or two while I'm at it, and change the Manual trans. oil, (not to be confused with trans fats, or triglicerides :) ). Also might be able to change the differential oils while I'm at it too. I've had some trouble shifting when starting out in the mornings through the winter, so I'm considering full synthetic.

Questions:
1. What is the safest and best viscosity/brand/type to replace in the Manual gear box, and in both differentials?
2. What do you think about synthetic, as oppossed to dino for these applications, and why?
3. Any tricks to changing these that aren't described in the Haynes Manual?
4. Lastly, Do you recommend any special additives that might help keep the gaskets plyable, or be beneficial?


my manual for my 03 impreza says 75W90. check your manual, it should be in there... mine has a diagram with different viscosities and temps...

#3 Smpol19

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Posted 04 May 2005 - 06:30 PM

I'm running Mobil 1 75w90 now, I've heard some people say its not good Subaru transmissions and I get a bit of a grind going into 3rd. I put it in when i bought the car used with 70k miles on it and it definitly made things smother. I ordered some Redline 75/90 NS which there have been a lot of good things said about so I should be puttin that in tomorrow i'll post on how it feels. If that doesn't work out I'm probably just going to go back to a quality dyno gear oil. I've also heard some good things about Castrol Syntorq (sp?) but I've had trouble finding this in the US. I'll post tomorrow night on how the Redline feels. Below is a link to a very long indepth article on this topic on nasioc. Let us know what you do put in and how you like it.

http://forums.nasioc...ad.php?t=416514

#4 Setright

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Posted 04 May 2005 - 11:57 PM

Synth is ok. The grinding into third is a Subaru trait. Some oils may mask this better than others. Make sure your clutch linkage is tensioned correctly. Too loose and it will cause hard shifting since the clutch plate never really releases if there is too much slack.
(Too tight and the clutch will slip as you release the pedal in higher gears)

I prefer Mobil1 tranny oil over Redline. And I prefer Castrol over Mobil, but apparently TAF-X or "Syntorq" is very expensive stateside.

Rear diff doesn't need added friction, only lubrication, so an oil that is optimised for "transaxles" like your manual Sube tranny, will not be optimal for the rear diff.

(That's where Castrol Syntrax comes in handy)

#5 blitz

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Posted 05 May 2005 - 07:43 AM

Tranny: Redline MT-90
Rear diff: Redline Shockproof Ultralight
-

#6 bfg9k

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Posted 05 May 2005 - 09:32 AM

I have the Royal Purple 75w90 gear oil in the front & rear diffs on my 98 auto Legacy. The car had a tranny rebuild in the winter, and the shop put in 90w dino as was recommended to them by a dealer service tech. I switched it over to the RP, seems to run fine.

#7 (goldfish)

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Posted 05 May 2005 - 11:02 PM

I've read something about special addatives for the v-lsds. is that (the lsd) oil changed with the tranny, is the castrol good for this? I'm sure all my gear oil needs to be changed.

#8 Equalizer

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Posted 16 May 2005 - 04:17 PM

Thanks for all of the responses, guys!

I found the real problem that was causing the noise and vibration in the front end. It turned out to be a wheel bearing. I ruled it out initially since the wheel had no play, but apparently the big 1 piece bearings keep it tight, when going bad, unlike the 2 piece ones on the older GLs. I still plan to change the gear oils, but your different responses made it a tougher decision than I 1st thought it would be:-\ :slobber: .

Any other recommendations, or if you want to expand on your answers any more, are appreciated. I'll be checking back.

Thanks again

#9 hklaine

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Posted 16 May 2005 - 07:43 PM

I have been running RedLine 75W90NS with great results! I have this GL-5 oil in my transaxle as well as (non-LSD) rear. This oil also comes recomended by Cobb.

I also run the RedLine DT4 ATF in the 5MT of my SHO (calls for ATF) and the shifts are great!

Take a look at their site (www.redlineoil.com) for the full product line and descriptions. When shopping for an oil keep in mind:

Viscosity Range (mfr. suggested based on environmental temp range)
Oil Temperature Range
Fluid Type (i.e. GL-X)
Syncro Compatibility

-Heikki

#10 Smpol19

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Posted 16 May 2005 - 11:41 PM

I've had the redline 75w90NS in for about 1500 miles now. It felt great at first but when its warmed up I still get a bit of a grind when I shift into third from 2 abouve 3500 rpm. I'm not really sure how much of a problem this is. I'll probably go back to regular stuff next time I change it just because i'm not willing to spend $50 bucks on gear oil all the time unless it really compleatly fixes the problem.

#11 f15xxx

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Posted 17 May 2005 - 08:40 PM

whoa! after trying redline 75-90 and 75-90ns in my 99 leg l sedan 2.2 5mt and still getting a little grind and way too much pita going into 1st at a stop sign, please, please, try redline mt-90. this stuff works, case closed, period. so what if it's not gl-5, who's going to thrash a nice car anyway?

#12 bulwnkl

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Posted 19 August 2005 - 10:00 PM

Hi,

I'm pretty new to posting here, but I wanted to re-awaken this thread. Has anyone had wear problems from using the non-GL-5 MT-90 in their 5-speed?

Has anyone tried Specialty Formulations' MTL-R? See www.specialtyformulations.com

I'd really love to hear from anyone who has tried the SF product. 75W90 GL-5 but made specifically for transmissions.

Anyone?

#13 Setright

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Posted 20 August 2005 - 01:59 AM

I am still working on what is the best oil for Sube gearboxes. Seems to me the real solution would be for the Sube engineers to admit their mistake and beef up the synchro on third gear.

If you go for a synthetic oil, try to get hold of that rates 75W-85 or 75W-80. These are thinner and are easier for the synchro rings to press aside, so they can get surface contact and actual match gear speeds.

A straight 80W will also do.

#14 rweddy

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Posted 20 August 2005 - 09:04 AM

I'm running Mobil 1 75w90 now, I've heard some people say its not good Subaru transmissions and I get a bit of a grind going into 3rd. I put it in when i bought the car used with 70k miles on it and it definitly made things smother. I ordered some Redline 75/90 NS which there have been a lot of good things said about so I should be puttin that in tomorrow i'll post on how it feels. If that doesn't work out I'm probably just going to go back to a quality dyno gear oil. I've also heard some good things about Castrol Syntorq (sp?) but I've had trouble finding this in the US. I'll post tomorrow night on how the Redline feels. Below is a link to a very long indepth article on this topic on nasioc. Let us know what you do put in and how you like it.

http://forums.nasioc...ad.php?t=416514

Do not use Mobil1 or any other GL5 synthetic lubricant in your tranny!!These are too slick for the gears/ syncros and this is why they work poorly and you get grinding!!! Check out http://www.ultimates...ead.php?t=15000

They only lubes I would ever use are Redline MT-90 or Castrol TAF-X or "Syntorq"




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