Question: Trans. & Diff. Oils

[oldberkeley]

I appreciate the answers I had to my question the other day about what type of maintenance I should be doing on my 1997 Legacy Outback, 2.5 engine,manual transmission.

 

I've been working on it on and off for the past few days, I'd like to change the transmission & differential oils tomorrow. I've been reading A LOT of old posts (it's kind of addictive!) and I'm a bit confused about the type of oil to use in the transmission and differential.

 

1. Is it ok to just simply use the same oil in both? If so, what is a reasonably-priced, readily-available in most stores oil that I could use? I'm not going to do this every week, so I'm certainly willing to pay the price for synthetic if that is what should be used.

 

2. A poster from last week asserted that manual transmissions are better with regular gear oil than synthetic, something about screwing up the "synchro" (sorry, not sure what that means!)Again, it's not the money, I want to use the correct product.

 

3. I bought a plastic funnel with a long plastic tube attached. Will I need any other specialized equipment/tools?

[rweddy]

I appreciate the answers I had to my question the other day about what type of maintenance I should be doing on my 1997 Legacy Outback, 2.5 engine,manual transmission.

 

I've been working on it on and off for the past few days, I'd like to change the transmission & differential oils tomorrow. I've been reading A LOT of old posts (it's kind of addictive!) and I'm a bit confused about the type of oil to use in the transmission and differential.

 

1. Is it ok to just simply use the same oil in both? If so, what is a reasonably-priced, readily-available in most stores oil that I could use? I'm not going to do this every week, so I'm certainly willing to pay the price for synthetic if that is what should be used.

 

2. A poster from last week asserted that manual transmissions are better with regular gear oil than synthetic, something about screwing up the "synchro" (sorry, not sure what that means!)Again, it's not the money, I want to use the correct product.

 

3. I bought a plastic funnel with a long plastic tube attached. Will I need any other specialized equipment/tools?

 

1. Do not use use synthetic GL5 in your tranny, this is fine for rear end but not for the synchors in your tranny.

For your tranny use Redline MT-90 or Castrol TAF-X or "Syntorq"

 

2. See above

 

3. You will not need this, funnels for Autos. Manuals have fill holes on the transmision.

 

Have fun and try not to get too messy!!

[subiedoobydoo]

Hi, I have 4 Generation one Legacys, (1990-1994) and three of them are automatic, including my newest addition a mint 1994 Legacy Turbo Wagon. I have been using AMSOIL SYNTHETIC ATF and its been a godsend to say the least. This is the best fluid to use if you want your transmission to last. Go to www.amsoil.com and read up on the products. I use all their products in my Legacys, and my cars have had no problems. Im not sure what the oil capacity is of your 97 legacy, but in my 93 it is 8.8 quarts. You need to do a complete flush, in order to get all the old fluid out of the torque converter, just draining the from the drain plug will only drain out about 4 quarts or so. Obivoulsy you will never get all 100% of the old oil out even when doing a full flush, but it will be close. What I do is drive the car for about a month or so after the first flush, and then drain it again, this time just from the drain plug, which again drains out about 4 quarts. Then I add more synthetic fluid and check, doing this a few more times after the initial complete flush, ensures that your have 100% Synthetic ATF in the tranny. I cant tell enough times, how what a difference its made in my legacys. My 93 Legacy has 244k original miles on the tranny and it shifts lilke new and so smooth. Trust me, you wont be disappointed. Im just about to do the same thing to my 94 Legacy Turbo wagon, this week. Also use the synthetic gear oil in your differentials, and in your manual tranny, it works wonders. IMO this is one of the best preventative maintenance that you can do, which in turn will save you a ton money down the road. Good Luck, and I wouldnt wait too long to try the Amsoil Synthetic ATF.

 

 

91 Legacy L AWD sedan Auto.

93 Legacy L AWD wagon Auto.

94 Legacy L AWD wagon 5-speed

94 Legacy TURBO AWD wagon Auto.

[oldberkeley]

Well, there it is again! One person says DEFINITELY to use synthetic, the other person says DEFINITELY do not. Which is correct?

Hi, I have 4 Generation one Legacys, (1990-1994) and three of them are automatic, including my newest addition a mint 1994 Legacy Turbo Wagon. I have been using AMSOIL SYNTHETIC ATF and its been a godsend to say the least. This is the best fluid to use if you want your transmission to last. Go to www.amsoil.com and read up on the products. I use all their products in my Legacys, and my cars have had no problems. Im not sure what the oil capacity is of your 97 legacy, but in my 93 it is 8.8 quarts. You need to do a complete flush, in order to get all the old fluid out of the torque converter, just draining the from the drain plug will only drain out about 4 quarts or so. Obivoulsy you will never get all 100% of the old oil out even when doing a full flush, but it will be close. What I do is drive the car for about a month or so after the first flush, and then drain it again, this time just from the drain plug, which again drains out about 4 quarts. Then I add more synthetic fluid and check, doing this a few more times after the initial complete flush, ensures that your have 100% Synthetic ATF in the tranny. I cant tell enough times, how what a difference its made in my legacys. My 93 Legacy has 244k original miles on the tranny and it shifts lilke new and so smooth. Trust me, you wont be disappointed. Im just about to do the same thing to my 94 Legacy Turbo wagon, this week. Also use the synthetic gear oil in your differentials, and in your manual tranny, it works wonders. IMO this is one of the best preventative maintenance that you can do, which in turn will save you a ton money down the road. Good Luck, and I wouldnt wait too long to try the Amsoil Synthetic ATF.

 

 

91 Legacy L AWD sedan Auto.

93 Legacy L AWD wagon Auto.

94 Legacy L AWD wagon 5-speed

94 Legacy TURBO AWD wagon Auto.

[rweddy]

Well, there it is again! One person says DEFINITELY to use synthetic, the other person says DEFINITELY do not. Which is correct?

 

I did say to use synthetic just not gl5 synthetic like Mobil One in the tranny.

Redline MT-90 and Castrol TAF-X/"Syntorq" are GL4 type syntheic oils.

These are the best to use in a Subaru where the tranny and front diff share the same fluid.

[oldberkeley]

I'm sorry, I totally misunderstood, I'm new at this! Are the two products you mention easy to find?

I did say to use synthetic just not gl5 synthetic like Mobil One in the tranny.

Redline MT-90 and Castrol TAF-X/"Syntorq" are GL4 type syntheic oils.

These are the best to use in a Subaru where the tranny and front diff share the same fluid.

[rweddy]

I'm sorry, I totally misunderstood, I'm new at this! Are the two products you mention easy to find?

 

 

No worries at all

 

Redline is at dealers

Castrol at Dodge/Chrysler dealerships, beware it is 4 time more expensive than redline here in the states.

[friendly_jacek]

No wonder this guy is confused. He asked for an advice on MT and got one on AT. Go figure!

 

Hi, I have 4 Generation one Legacys, (1990-1994) and three of them are automatic, including my newest addition a mint 1994 Legacy Turbo Wagon. I have been using AMSOIL SYNTHETIC ATF and its been a godsend to say the least. This is the best fluid to use if you want your transmission to last. Go to www.amsoil.com and read up on the products. I use all their products in my Legacys, and my cars have had no problems. Im not sure what the oil capacity is of your 97 legacy, but in my 93 it is 8.8 quarts. You need to do a complete flush, in order to get all the old fluid out of the torque converter, just draining the from the drain plug will only drain out about 4 quarts or so. Obivoulsy you will never get all 100% of the old oil out even when doing a full flush, but it will be close. What I do is drive the car for about a month or so after the first flush, and then drain it again, this time just from the drain plug, which again drains out about 4 quarts. Then I add more synthetic fluid and check, doing this a few more times after the initial complete flush, ensures that your have 100% Synthetic ATF in the tranny. I cant tell enough times, how what a difference its made in my legacys. My 93 Legacy has 244k original miles on the tranny and it shifts lilke new and so smooth. Trust me, you wont be disappointed. Im just about to do the same thing to my 94 Legacy Turbo wagon, this week. Also use the synthetic gear oil in your differentials, and in your manual tranny, it works wonders. IMO this is one of the best preventative maintenance that you can do, which in turn will save you a ton money down the road. Good Luck, and I wouldnt wait too long to try the Amsoil Synthetic ATF.

 

 

91 Legacy L AWD sedan Auto.

93 Legacy L AWD wagon Auto.

94 Legacy L AWD wagon 5-speed

94 Legacy TURBO AWD wagon Auto.

[Setright]

Valvoline Synpower 75W-90 should also be easy to get a hold of - and it's at least as good as Syntorq.

 

Synth GL5 is good for me.

 

 

Yes, the funnel and tube will come in handy on the transmission. Slide the tube into the filler hole and pour slowly down the funnel. It'll swallow about 3.5 liters, but I prefer to fill 3.0 and then top it off after a drive and four hour cool down.

 

The rear diff is tricky to fill unless the oil bottle itself has a tube spout. There is room - just - to lift the bottle up underneath the fuel tank and squeeze oil in.

 

Otherwise a very long tube can be used to fill from above the car. Insert in the diff and get it out around the rear left wheel...

[bulwnkl]

The thing about GL-5 gear oil is that it's nearly all built with rear-ends and unsynchronized transmissions (like in semi-trucks) in mind, but NOT with synchronized transmissions (like in a Subaru) in mind.

 

The thing with GL-4 gear oils like RedLine MT-90 or Castrol Syntorq, or Syntrax or whatever it is, is that they do not provide the protection necessary for hypoid gears. What are hypoid gears? There's a set of them in your transmission called the front differential. Not all differentials are hypoid, but all Subie fronts are.

 

So, do you want the protection your gears need, or do you want good shifting? The best widely-available compromise seems to be a dino GL-5 gear oil. They don't shift terrific, but they seem to be better than most of the synthetic GL-5s.

 

The only fluids I know of that meet the required GL-5 spec and are built for synchronized transmissions are RedLine 75W90NS and Specialty Formulations' MTL-R. As you've likely read on here and elsewhere, the 75W90NS is usually liked, but many times not. Everyone I know of who has used the Specialty Formulations product likes it better than anything else they've tried.

 

I have RedLine in now, but not the NS. It actually works reasonably well for me, but I don't shift fast and I have an older XT-6. I'm buying some of the MTL-R this week, so if you can wait a couple/few weeks, I'll have some experience with the SF product as well. It's a full-synthetic (PAO/Ester combo) that's specifically built for excellent shifting, but it also meets the GL-5 protection requirements of your front diff.

 

rweddy, how many miles have you put on any one transmission after putting in MT-90 or the Castrol product?

[Setright]

I beg to differ. The GL rating doesn't exclude hypoid gears. GL4 is perfectly suited for heavily loaded hypoid drives.

[bulwnkl]

I beg to differ. The GL rating doesn't exclude hypoid gears. GL4 is perfectly suited for heavily loaded hypoid drives.

 

I too will differ with you. GL-4 is not at all suitable for heavily loaded automotive hypoid units. It may be suited for lightly loaded hypoid units. Subaru didn't choose GL-5 as a required specification out of the air.

 

Here is some information I pass along from the RedLine tech department:

 

"GL-4 Denotes lubricants intended for axles with spiral bevel gears

operating under moderate to severe conditions of speed and load or

axles with hypoid gears operating under moderate speeds and loads.

 

GL-5 Denotes lubricants intended for gears, particularly hypoid

gears, in axles operating under various combinations of high speed

shock loads and low speed, high torque conditions."

 

Please show me some 'heavily loaded' automotive hypoid differentials which do NOT specify or recommend a GL-5 rating. No cherry picking back before the GL-5 spec was created.

[rweddy]

The thing about GL-5 gear oil is that it's nearly all built with rear-ends and unsynchronized transmissions (like in semi-trucks) in mind, but NOT with synchronized transmissions (like in a Subaru) in mind.

 

rweddy, how many miles have you put on any one transmission after putting in MT-90 or the Castrol product?

 

Well stated Bulwnkl!!

 

This is totally true and this is why I do not run Redline MT-90 in my Subaru’s (great for my other cars with manuals though) I run 75W90NS. I had over 50k on my 91 and over 30k on my 96.

 

This is my question and answer from Redline.

 

I am trying to figure out what type fluid I should run in my vehicle manual transmissions. I have used your MT-90 in multiple vehicles with great success.

 

My question revolves around running a GL4 transmission fluid in a Subaru where the transmission and front differential share the fluid. The factory recommends using GL5 fluid but I have run GL4 in most all my manual box and the difference between running GL5 and GL4 is night and day, with the GL4 working sooo much better.

What type of fluid would you recommend I run in a Subaru with shared transmission and front differential?

 

Thanks

 

Richard, In your Subaru transaxle where the GL-5 gear lube is called for I would recommend the 75W90NS, I would expect the shiftability to be close to the MT-90. The NS fluids have no friction modifier so are not to slippery for the synchros the problem with most GL-5 gear oils. The 75W90 would be suitable for the rear differential.

 

Regards, Dave

Red Line Oil

[bulwnkl]

Well stated Bulwnkl!!

 

This is totally true and this is why I do not run Redline MT-90 in my Subaru’s (great for my other cars with manuals though) I run 75W90NS.

 

Oh, I misread/misunderstood. My mistake; sorry.

[Setright]

Well, based on information I obtained directly from the API, I wouldn't worry about using a GL4 oil in my transmission.

 

As it happens, the Valvoline Synpower that I am running spans the GL scale from 3 to 5. In full accordance with the API who specifically state:

 

"These designations also recognize the possibility that lubricants may be developed for more than one service classification and may be so designated."

 

 

I understand that challenging the engineers who chose the GL5 requirement for the Sube gearbox seems a bit obnoxious, but consider that it's probably the same engineers who after 30 years(!) still can't fit a big enough synchro cone on third gear....

 

We wouldn't be having this discussion if 2nd to 3rd wasn't accompanied by a kerrrUNCH!

[bulwnkl]

We wouldn't be having this discussion if 2nd to 3rd wasn't accompanied by a kerrrUNCH!

 

Yes, I suppose you are right. OTOH, my older Subaru (XT-6) doesn't have this problem. Imprezas at least certainly do, though. It appears to me that Subaru has altered the synchros over time to try to address shift quality somewhat while dealing with both increasing power/torque levels of newer engine series and also the GL-5 rated oil that their hypoid transaxles require.

 

I am aware that a fluid can be multi-rated. IOW, it can be a GL-4 and a GL-5 at the same time. This is essentially because the GL-5 rating requires more of the same thing that GL-4 requires. In point of fact, the Extreme Pressure/Anti-Wear (EP/AW) additive in GL-4 and GL-5 lubes from most oil companies is exactly the same thing. Here is some info from the lead blender/chemist for a West Coast oil company:

 

"GL-4 vs GL-5 other than vis grade is only the difference in amount of AW/EP additive put into the oil. Most oil companies will use 1 additive package for both Gl-4 and Gl-5 the difference is a GL-4 will take a treat of 2%wt and a GL-5 will be a treat of 7%. same additive just more..."

 

You see, the lower additive rate of a GL-4-only fluid is simply insufficient for good durability under the extremely high sliding forces seen in a hypoid differential. Remember that not all hypoid gears are in differentials.

 

Please don't misunderstand me; I fully appreciate and respect anyone's prerogative to choose what fluid they use in any given application. I also think it is important to understand the implications of such decisions.

 

I asked the wrong person above, so I'll ask you, Setright: How many miles have you put on any one Subaru transmission following the installation of a GL-4-only (not multi-rated to include GL-5) fluid?