Trans/rear dif oil?

[ckb1985]

I just switched to redline lightweight shock proff in my tranny and redline 75w90ns in my rear diff. I didnt have an issue with the rear diff but definetly did with the tranny. It would grind a little when down shifting from 2nd to 1st even if only moving 1 mph. Now it dosnt do that and it shifts super smoth. oh and the best part was I pulled the plug on a tranny that most likely had never had its oil changed in 93,000 miles and not a darn thing was stuck to the magnet cept some powder...

[williaty]

Unless you're really skinny, you'll need to have the car on stands to drain the tranny, and probably to drain and fill the rear diff. The car will need to be level for filling both the tranny and rear diff. having the car set nose-up is probably an advantage for draining the rear diff. I'm not sure how pitch will affect draining the tranny. I'm not sure where the tranny drain plug is within the sump.

Since you have an 02, you'll need some crazy big metric hex to get the tranny drain plug in and out. You'll also need the copper washer to seal the tranny back up.

You'll need a 1/2" square bit (a.k.a. the business end of a 1/2" drive breaker bar) to remove the rear diff plugs. REMOVE THE TOP (FILL) PLUG FIRST! IF YOU GET THE BOTTOM (DRAIN) PLUG OUT FIRST AND THEN CAN'T GET THE TOP ONE OUT IT REALLY SUCKS. Remove the top plug, remove the bottom plug, wait for it to stop dripping, replace the bottom plug, fill through top plug with oil until oil begins to spill back out, replace top plug.

The easiest way I've found to fill the rear diff is to buy about 3' of 1/2" ID clear tubing and a funnel that the tubing will jam up onto. Hold the tubing in the fill hole of the rear diff and have someone else pour the oil into the funnel/tube held up high.

Filling the tranny seems to best be done by removing the IC (if WRX) or air box (if RS) and then using a really damned long funnel.

Torque spec for the tranny drain plug is 51.6ftlbs. Torque spec for the rear diff plugs is 36.2ftlbs.

Capacity for the tranny is 3.7qt, capacity for the rear diff is ~0.8qt.

The shop manual calls for fluid packing on the threads of the rear diff plugs. I've never noticed that line before and I don't leak, but take that with a grain of salt.

[Superorb]

Thanks a lot man. I read a few minutes ago that some people fill the tranny through the dipstick. I didn't even know there was one... I've got 1/2" and 3/8" tq wrenches and all sorts of other hand tool goodies Now I guess all I'm missing it the oil, time, and either four jackstands or a lift After the holidays.

[neener]

why did you say NOT to use the 75w90NS GL-5 gear oil? you might be able to take a shot at where im going with this.

[williaty]

I'm a .sig! I RULE!

The NS in the 75w90NS signifies that the additive package does not contain the friction modifiers. In other words, 75w90NS is Not as Slipery. This is necessary in the transmission to provide enough friction for the synchros to function.

The regular 75w90's additive package contains the friction modifiers and is therefore much slipperier than the NS variant. This results in lower parasitic drag in the rear diff.

If you were to put the regular 75w90 in the transmission, the synchros would not experience large enough frictional forces to spin up the input shaft and massive grindage results. This is precisely why most synthetic oils suck in the subaru tranny.

[Superorb]

Ok.

Tranny: Cocktail

1qt Redline lightweight shockproof
1qt Pennzoil Synchromesh
2qt Castrol HypoyC 75w-90

Rear Dif: 75w90 GL-5 NOT NS

[williaty]

Yeah, the important thing is to get the full quart of shockproof in there to protect the front diff and the full quart of synchromes in there to protect the synchros. Then just slowly add little splashes of the Castrol until the dipstick reads right.

[Superorb]

Ok. It's going to be a while before I'll be able to do this, but I'll keep an eye out for everything. Do I pour them in separate or premix them? I don't think it will matter since they'll be sloshing around in the case anyways.

What's this I've heard about some Subaru Performance Tranny Fluid?

[williaty]

Just pour them in and let god sort em out.

Subaru makes a dino-based lube for the tranny. Some people run it with great results. However, the minimum quantity you can buy requires a deep water port beside your house because it's delivered by tanker.

[neener]

I'm a .sig! I RULE!

haha ya i honestly could not stop laughing at that comment because its very true.

on the other hand im confused b/c you said NOT to use the NS in the rear diff the first time and i could have sworn that it was ok to when i researched for my self when i was in the same situation about looking for tranny oils. then in the last post you said NOT to use it in the trans, well i knew that but now im just confused

[williaty]

Upon re-reading it, I still think what I said in the last post is correct, but I've been known to write things in severely obfuscated verbiage.

To Recap:

The 75w90NS is less slippery than the 75w90

The rear diff would like the slipperiest possible oil, hence you feed it the 75w90.

The transmission wants only a moderate amount of slipperiness, hence you feed it the 75w90NS.

If you were to put the really-slippery regular 75w90 into the transmission, you'll start grinding gears.

If you were to put the less-slippery 75w90NS into the rear diff, you'd get slightly worse gas milage and slightly higher operating temps.

[Superorb]

Just pour them in and let god sort em out.

Subaru makes a dino-based lube for the tranny. Some people run it with great results. However, the minimum quantity you can buy requires a deep water port beside your house because it's delivered by tanker.

All right. I'll start collecting the necessary fluids for the yet undetermined date. I appreciate all the help

EDIT: another thing; is it ok to use the 80w90 or only the 75w90 is best.

[williaty]

using 80w90 rather than 75w90 just means the bits won't be protected as well before the oils reach operating temperature. I have no idea how much of a difference 75 vs 80 is though.

[Superorb]

When I leave it in gear and have the clutch pressed to coast to a turn or speed bump, it makes a whirring sound almost similar to backing up in a Honda. Is that normal/safe to do?

[williaty]

These trannys make more different kinds of crazy noises than anything I've ever heard. Even more fun, they don't all make exactly the same sounds. About the only advice I can give you that when your car starts making different noises, you need to pay attention.