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Premium Member
2015 Highlander AWD XLE 6AT
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Discussion Starter #1
With 12,60X miles on the odometer, I'm getting ready to change the gear oil in the '09 Forester's MT/front diff and rear diff. I have a supply of Subara Extra-S 75W90 gear oil for both.

Subaru specs Threebond 1105 as the sealer for the rear diff plugs. This is not available locally, so I'm thinking about using Permatex 59214 High-Temp Thread Sealant instead.

Comments?

Thx,
Jim / crewzer
 

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Premium Member
2015 XC diesel CVT
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4,053 Posts
It's a taper thread if memory serves, so damn-near anything will do...
 

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2015 Forester X 6MT 6-Gear Manual
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As long as permatex says its compatible with oil and/or water.
 

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2015 Forester X 6MT 6-Gear Manual
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1,373 Posts
Maybe you want to try redline MT90 or Amsoil in the MT. MT works better and synchros will last much longer with GL-4 specailty MT oil than GL-5 as there is no hypoid in the case.
 

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2015 Highlander AWD XLE 6AT
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Discussion Starter #5
As long as permatex says its compatible with oil and/or water.
Info from the product TDS:

Chemical resistance: Gasoline, oil, water, glycol, hydraulic fluid, freon, transmission fluid, brake fluid​
Looks like we're good to go!

I sorta understand the notion that the specialty MT GL-4 could be better for the MT, but it shares the fluid with the front diff. I've already got the Extra-S, but I'll look into this for next time.

Thanks!
Jim / crewzer
 

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The Modfather
2019 Impreza 5dr Sport - Manual
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8,054 Posts
I've been using teflon tape on the plugs since 97 and never had an issue. Just keep it off the first few threads and only snug the plug, don't go super tight.
 

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2015 Highlander AWD XLE 6AT
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Discussion Starter #8
Thanks, guys.

I've got both the 59214 and teflon tape available in my garage. I suspect Subaru believes the liquid sealer can be applied faster, but I've also had good luck with (correctly wound) teflon tape.

Thanks again,
Jim / crewzer
 

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2019 Crosstrek 2018 XT
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Waste of time..you don't need anything. I have changed it 5 times on 2 cars ..torqued it to 30 ft. lbs and not a problem
 

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Administrator
2007 Forester Sports XT 4EAT
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If you use teflon tape, make sure you use the yellow & not the white. The Yellow teflon tape is for use with petroleum products. :wink:

Bobby...

My MODding Journal
 

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just use THIS on all threads that you want sealed/prevent from galling.

I'm not crazy about teflon tape in automotive applications (although I know it's widely used). And never liked silicone-based anaerobic sealants on threads either (again, I know they are widely used)

Also, i'm sure it *will* seal with nothing on the threads (it's not highly pressurized), but i think it's more about galling due to the dissimilar metals.
 

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2015 Highlander AWD XLE 6AT
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Discussion Starter #12
Thanks for the additional pointers. However, the deed is done! :icon_biggrin:

I used the Permatex 59214 on the rear diff plugs, reused the MT / front diff's drain plug gasket, and used 4.2 liters of Extra-S 75W90 gear oil. Everything's all buttoned up, torqued, and road tested.

The 1/2" female-to-13mm male square drain plug adapter and the Great Neck T70 star driver bit both worked perfectly.





The attached pic shows the rear diff's drain plug with a nasty coating of gray gunk on the magnet after 12,608 mostly highway miles. The old oil was rather gray as well. The MT's drain plug magnet attracted a much smaller amount of metal, and its old oil was not as dirty. I like the color of the new oil!

Thanks to all who have done this before and posted their comments and suggestions.

Regards,
Jim / crewzer
 

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2008 LL Bean (4EAT)
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Maybe you want to try redline MT90 or Amsoil in the MT. MT works better and synchros will last much longer with GL-4 specailty MT oil than GL-5 as there is no hypoid in the case.
There are hypoid (spiral or helically cut) gears in the manual transmission.
The Owners Manual specifies only API classification GL-5.
Using GL-4 will cause harm according to this post by a mechanic who specializes in Subaru manual transmissions:

... GL-4 and GL-5 are VERY different fluids...

The Subaru transmission is fairly unique... First gear is very very unique. There is NO bearing. First gear rides, solely, on a thin film of gear oil. This is a major reason that Subaru's require GL-5 and NOT GL-4. In addition to this, there are only a handful of bearings in the tranny, including some thrust surfaces that, again, rely on a thin film of oil...

With no physical bearing on first gear, film strength and viscosity are important. That is why GL-5 is required.... A GL-4 fluid will be incapable of handling these pressures (and, I have in fact seen a first gear on the output shaft weld itself to said output shaft thanks to using a GL-4 fluid)...

There are other reasons as well. Mainly the hypoid pinion. Hypoid gears put a lot of stress on oil, and this is compounded by the fact that the pinion shaft runs THROUGH the output shaft with ridiculously shallow clearances... a failure of the fluid will cause the pinion to bind against the ring gear, and effectively knife-edge both parts. If you continue to drive under these circumstances, you WILL strip every tooth off of the pinion shaft. I've actually seen this as well, in a few race cars running Redlines MT90.

GL-5 is backwards compatible. Transmissions that are good with GL-4 will do just fine with GL-5. Transmissions requiring GL-5 CANNOT use GL-4....

http://www.subaruforester.org/vbulletin/f88/first-gear-grind-kind-24613/index2.html#post284043
 

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2008 Forester X Premium 5MT
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Waste of time..you don't need anything. I have changed it 5 times on 2 cars ..torqued it to 30 ft. lbs and not a problem
I agree, tapered pipe thread style plug. No "need" for any thing.

Using some thing wont hurt, however
 

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2008 LL Bean (4EAT)
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Waste of time..you don't need anything. I have changed it 5 times on 2 cars ..torqued it to 30 ft. lbs and not a problem
Same here. I changed the rear diff oil once, just torqued the drain plug, and it's been bone dry for the past 3000 miles.
 

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2008 LL Bean (4EAT)
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...The attached pic shows the rear diff's drain plug with a nasty coating of gray gunk on the magnet after 12,608 mostly highway miles. The old oil was rather gray as well...
Several people had posted that, which made me change my 2008's rear diff at 15,000 last Fall, and I found the same thing. Gray oil with a load of black gunk on the magnet. Yet the oil in the front diff was OK. Thanks for showing the photo of the gunk.
 

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2015 Highlander AWD XLE 6AT
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Discussion Starter #17
^ Glad to help. Let's just say it's partial payback for all of the assistance the forum has been to so many of us.

Regards,
Jim / crewzer
 

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Premium Member
2015 Highlander AWD XLE 6AT
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4,255 Posts
Discussion Starter #18
Another interesting GL-4 vs GL-5 discussion here; see comment from "webfors".

HTH,
Jim / crewzer
 

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2010 Forester 2.5X
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1,692 Posts
Got about 11k on mine and about to change the MT oil and the rear.
Only Extra S in LA I can find is $14.50 per qt. at LaPuente dealership. :icon_frown:

Anybody in LA got Extra S oil?
 

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Premium Member
2015 Highlander AWD XLE 6AT
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4,255 Posts
Discussion Starter #20 (Edited)
Only Extra S in LA I can find is $14.50 per qt.
Fred Beans has it for for $55 / 5 qts. + $17.75 shipping = $14.55 / qt.

I got mine several months ago on the East Coast for $60 / 5 "liters +" + $16.50 shipping = $15.30 / "liter +".



Imagine that! :icon_rolleyes:

However, 42 Autosports now says that their "5 liter package deal" for $75.00 includes shipping. :icon_cool:

HTH,
Jim / crewzer
 
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