few questions about differentials

[MetalNeverDies]

1. what fluid is best for the diff and tranny. subaru oem? or should i get royal purple, redline, or mobile one?

2. what all do i have to do to drain both the differentials and the tranny.

3. how horribly hard is it to swap the 2.5RS non locking or anti slip diff. for the wrx locking diff? if this isnt hard how about swaping for sti diff's.

[REDrum]

All my comments are based on the 5MT gear box, and specifically MYs 2002 to 2007

1. what fluid is best for the diff and tranny. subaru oem? or should i get royal purple, redline, or mobile one?

Big issue w/ Subarus...
The syncros are very sensitive to slippery gear oils, and will not engaged quickly if too slippy an oil is used. Synthetic by design is very slippy. Its VERY hard to find synthetic GL5 that permits quick (smooth) engagement for the 5MT. "Best" or "worst" is judged on how easily the sycros engage. Someone who is not sensitive to this will force the engagement and incur damage. OEM dino oil is proven very good (Its Castorl, me thinks...) Mobil I is just about the worst (slippiest). Royal purple is VERY good product, but a tad too slippy for my gear box (yes each gear box will react to each oil slightly different). I've tried 6 different gear oils and found Redline's Light Weight "Shockproof" ("smurf blood" as its know) to be the best, at least in my gear box box. OEM Dino is fine for daily driving, I'd only recommend syn in the 5MT for performance/competition use.


2. what all do i have to do to drain both the differentials and the tranny.

Open transmission drain plug and it will drain both front and center diffs. But, you may need a Torx 70 to do this. Since many people were having Jiffy lube add in syn gear oil, and drivers were grinding snycros, FHI fitted the gear box with a hard to find tool OEM drain plug

3. how horribly hard is it to swap the 2.5RS non locking or anti slip diff. for the wrx locking diff? if this isn't hard how about swapping for sti diff's.

Locking diffs on WRX ? I don't think so...(except w/ electronic DCCD)

Limited slip diffs, YES! Rear is easy for most mechanics to do. Front is very difficult even experienced mechanics will shy from it. Requires dropping and opening gear box, and realigning/shimming a bunch of finicky parts. I would only trust half a dozen shops in NE to do it. Rallispec, DSG, Vermont Sports Car, Andrewtech, are a couple. Center is not too bad for most mechanics. I had my front swapped to a helical (STI) LSD, and it completely changed how the car handles; best mod I did. But I did it durring a tranny rebuild/new gear swap. Otherwise it would have cost ~2,200 for a front LSD swap!!!

[MetalNeverDies]

with the swaping that you were talking about. for the rear i serioulsy just drop it in? or have to take apart the whole gear box? and the center is very difficult to?... could i just save up some cash and do a full sti tranny/front/center/rear diff swap?

[REDrum]

with the swaping that you were talking about. for the rear i serioulsy just drop it in? or have to take apart the whole gear box? and the center is very difficult to?...

On DYI difficulty scale 1 to 5 (w/ 1 being an anti sway bar swap and 5 being a shortblock swap)

Front diff = 4
Center diff = 3
Rear diff= 2

do a full sti tranny/front/center/rear diff swap?
LOL....don't forget axles and brakes too...that option will snowball.

Total installed cost will be >$5K if done by a shop. Materials alone for a used 6 speed driveline will cost ya $3K, on very good day. But yes its doable. By far, IMO, the biggest difference in performance between and STI and WRX is the driveline. I've spent >$20K tuning a WRX wagon into and STI wagon....and now complete, they offer a 5 door STI...:roll:

Check out rallispec.com for ideas

[MetalNeverDies]

well if i was gong to do a swap i would do a full probably. and it would be cooler to me than a sti 5 door cause mine is a saabaru and it would looks very sleeperish cause no one even knows what the hell a 92x is. plus it would be a relatively cool project.

[pigpen]

Since many people were having Jiffy lube add in syn gear oil, and drivers were grinding snycros, FHI fitted the gear box with a hard to find tool OEM drain plug

interesting. i had no idea that was the reasoning.

what do you think of amsoil? you said your suggestions were for the 5MT. do you happen to know the differences in fluid choices for a 6MT?


well if i was gong to do a swap i would do a full probably. and it would be cooler to me than a sti 5 door cause mine is a saabaru and it would looks very sleeperish cause no one even knows what the hell a 92x is. plus it would be a relatively cool project.

a saabaru STi would be one hell of a sleeper. that is one of the better swap ideas i've heard in a while.

[REDrum]

what do you think of amsoil? Notexperience w/ their gear oil in 5MTs



you said your suggestions were for the 5MT. do you happen to know the differences in fluid choices for a 6MT?


Anything GL5 works fine, its syncos are not a finicky as the 5MT. Many guys I know who run'm use Motul syn

[Jard]

what do you think of amsoil? you said your suggestions were for the 5MT. do you happen to know the differences in fluid choices for a 6MT?


Give AndrewTech a call and see what they say for 6MT fluid. I forget what the local dude used the last time we changed one in my garage.


+1 on Shockproof for the 5MT.

[ArcticWolf]

I'm running Amsoil severe gear 75w90 in my 5MT, and it doesn't seem to like it much at all. 5th has been noticeably harder to get into since putting it in there, the other gears have been a bit tougher as well.

Not sure if I should just leave it for the winter and change it once it thaws, or get it out of there ASAP and change it again after the thaw.

[pigpen]

well, hopefully that won't be the case with my 6MT. I just got a bunch of the Amsoil to do a change.

[me_jimmy]

well if i was gong to do a swap i would do a full probably. and it would be cooler to me than a sti 5 door cause mine is a saabaru and it would looks very sleeperish cause no one even knows what the hell a 92x is. plus it would be a relatively cool project.
+1 saabaroo STI