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Wanted: Opinion on Oils

3K views 20 replies 13 participants last post by  chris bunch 
#1 ·
Wanted: Locals Opinion on Oils

Hey guys, I'm looking to change my diff oil and tranny oil to see if I can eliminate a howling/whine noise I am getting at 60 mph and was wondering what kinda fluids you guys are using. Obviously looking for some sort of synthetic...

I've heard not to run Mobil1 in the tranny, but it's alrite in the differential...

ANY opinions are welcome, just thought I'd ask my local friends before I go out and ask elsewhere (and here I will probably get a better response)...

Thanks, Chris
 
#4 · (Edited)
Subaru has switched to a synthetic GL-5 that is made by GM, it works very well and seems to quiet noisy and help problematic shifting. I recently replaced mine in a transmission Bret had built 16000 miles ago, I beleive he put the synthetic in there and possibly some dexron as a detergent. It came out clear and smelled ok.

I put the Redline shockproof in my rear diff recently also, 5 teeth came out the drain hole with the stock fluid, which was black as coal after only 62000 miles. I noticed that though the fluid was black, it didn't have any metal in it. I put a light in the little fill hole and looked inside the diff. It was clean with no metal powder, but the teeth were missing from random locations on the planetary gears. The Redline seems to be fine in there and I am just waiting for the rearend to die eventually. My torque is now 265.7 uncorrected, 14psi, at the wheels at MAC. Die Rear Diff Die

edit- the GM synthetic is more expensive than the Redline. Also, I think you can't use the shockproof in the transmission, only in the rear diff.
 
#5 ·

I did mine last week and also used the vavoline, but got the 80-90. Walmart has it for less than $4 a quart. Before the change, my tranny was so crunchy that I had to drop to second(at a stop) before it would feed into 1st. Now it is fine. BTW, those are not just shredded synchros in that picture, there are a few teeth that came out of mine... :sadwave:
 
#6 ·
Chris G said:
I've heard not to run Mobil1 in the tranny, but it's alrite in the differential...
I am just curious were you heard this? I have run Mobil 1 full syn in my tranny, motor and rear diff for over 33 thousand mile with NO problems. I recently changed the tranny fluid, it was clear (well as clear as it can be) and not nearly as smelly from when I drained the stock stuff.

but each person is different and some cars react differently.
 
#7 ·
I've read about the Redline oils, but I am not sure which one to go with. Looks to me like the MT90 is GL4, and the 75w90 stuff is GL5.

Harvey, where did you pick up the Redline shockproof? Seems hard to find around where I am...

Does anyone know if I can pick up the GM stuff at a local parts store?

I feel like a n00b :rolleyes:
 
#8 ·
Matt Monson said:
I did mine last week and also used the vavoline, but got the 80-90. Walmart has it for less than $4 a quart. Before the change, my tranny was so crunchy that I had to drop to second(at a stop) before it would feed into 1st. Now it is fine. BTW, those are not just shredded synchros in that picture, there are a few teeth that came out of mine... :sadwave:[/QUOTE]

:whoa: :sadwave:

I'm afraid to flush my tranny now.
 
#9 ·
The problem with Mobil1 in the tranny is that the synchros want more friction that the Mobil1 provides to function optimumly. With too low friction, they will wear quickly and while you may not have any troubles now, you will likely wear them out quicker that way. This is the reason that I choose 80-90 dino oil for my car with 112k mi on the ticker. My synchros are hurting and I need that viscocity to make them work properly with how thrashed they are. Redline is the way to go if you choose syth...
 
#11 ·
I'm using the Redline MT-90 in my trans. The whining thing everyone complains about never bothered me so I really didn't notice much of a difference. Slightly smoother shifting. Also, I only had a small amount of metal shavings that were REALLY fine on the magnetic plug so that was good.
 
#12 ·
In my professional opinion as someone certified to do all sorts of crazy things with trannies. Valvoline Synpower 75-90w is absolutely worth it's weight in gold for subaru gear boxes. For rear differentials run Mobil 1 as it will help the diff. run a bit cooler/quieter. The problem with Mobil 1 in the tranny itself is that it doesn't have an additive package that generates enough friction between the synchros. Redline oils aren't GL5 rated (at least last I read they weren't) and can't be ran in subaru boxes without risking some long term damage.
 
#13 ·
analog_909 said:
In my professional opinion as someone certified to do all sorts of crazy things with trannies. Valvoline Synpower 75-90w is absolutely worth it's weight in gold for subaru gear boxes. For rear differentials run Mobil 1 as it will help the diff. run a bit cooler/quieter. The problem with Mobil 1 in the tranny itself is that it doesn't have an additive package that generates enough friction between the synchros. Redline oils aren't GL5 rated (at least last I read they weren't) and can't be ran in subaru boxes without risking some long term damage.
Matt, thanks for the advice...

I was thinking about running Mobil1 in the rear diff to begin with but wasn't sure...

Can this synpower be found at any "normal" autoparts store?

Thanks a lot guys, I really appreciate it!
 
#18 ·
Redline 75w-90 and 75w-90NS are both GL-5. The NS version stands for Non Slip or something along those lines and is what Redline recommends for Subaru trannies. Didnt help my tranny much though. Maybe look into how much you can get the new dealer juice for, might be worth the gamble, and also easier to find.
 
#21 ·
I've had Neosynthetic RHD in front and back of my 04 wrx. 16,000 no problems. It literally shifts exactly like brand new. I changed from stock at 3500 miles from new with already much metal shaving seen - glad i did. It's too expensive though. My take on it is this:

front:
I'm swiching to synthetic GL-5 with no friction modifiers (redline 75w-90NS)
Cobb recommends redline MT-90 for the front which is 75w-90 GL4 made for trannies - but subie recs GL-5.
Mobil 1, valvoline syn are too slippery and will shorten life of synchros and make them take longer to shift - in theory.
~3.8qt

rear:
neosynthetic RHD 75w-90 - or any slippery synthetic made for LSDiffs will probably do.
~750cc.

I think 15,000 miles / change of both is appropriate for how we all drive :)
 
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