Oil AND trans/diff fluid change at 1K miles?

[rotaryracer]

So, I'm at about 950 miles in my Leg GT Ltd sedan (5MT) and was planning to do an oil change at 1,000 miles. I've been pretty good about the 4K limit with a couple of solid pulls to break everything in nice-nice. While I've got the car in the shop, is there any benefit to having the transaxle and rear diff fluids changed at the same time? My thought is that if the early oil change will help remove any particles/shavings from the engine, wouldn't it make sense to hit the trans and diff and do the same? By the way, the car is niiiiiiiice and pulls like a freight train...SOOO much happier I got the Legacy instead of the STi... Jason

[Guest *Jedimaster*]

I was looking through my manual last night ans I believe it doesn't say anything about transaxle lube change until 60K miles or so.

[IwannaSportSedan]

the transmission, center diff, rear diff, front, etc. don't really break in the way an engine does. Pistons, rings, valves, and valve seats all need to break in-to each other to make efficient seals and mating surfaces under compression and combustion. The crank and cam bearings wear in a bit, and so would the bearings in the trans and diffs, but that is not as involved of a process as the cylinders in the engine, and don't generate much debris, and certainly no combustion by-products to get in the oil. The only reason I would change the trans and diff-fluids before recommended intervals would be to put in better stuff than the factory, such as Red-Line ATF or gear oil. If you do have it changed, and if yours is a GT, with a limited slip, make sure they use the proper addatives, or the LSD will wear pre-maturely.

[outahere]

[quote name='IwannaSportSedan'] If you do have it changed, and if yours is a GT, with a limited slip, make sure they use the proper addatives, or the LSD will wear pre-maturely.[/quote] It is my understanding that the rear limited slip in the GT is a sealed, viscous type. No special additive is required.

[rao]

[quote name='outahere'][quote name='IwannaSportSedan'] If you do have it changed, and if yours is a GT, with a limited slip, make sure they use the proper addatives, or the LSD will wear pre-maturely.[/quote] It is my understanding that the rear limited slip in the GT is a sealed, viscous type. No special additive is required.[/quote] That is correct. Changing the transmission and differential fluid is not necessary (but then changing the oil that early is also not necessary), but if it makes you feel better then have it done.

[IwannaSportSedan]

" I was not aware of that" - Johnny Carson It always helps to confirm those sorts of things with people in the know... Anyone know if one could put a quaiffe helical gear torque-sensing LSD in the Legacy GT, Rear or Front? Would a 1 or 1.5 way LSD in the front cause more understeer, or degrade handling? Is it pretty much a moot point for the street/snow?

[outahere]

[quote name='rotaryracer'] While I've got the car in the shop, is there any benefit to having the transaxle and rear diff fluids changed at the same time? My thought is that if the early oil change will help remove any particles/shavings from the engine, wouldn't it make sense to hit the trans and diff and do the same? Jason[/quote] IMO, there is no harm in doing a change on the rear diff oil. There will probably be some very fine metal debris from the ring and pinion breaking in, and since the gear oil is not filtered, a change is the only way to remove that contaminant. At the very least check the oil level. As far as the transaxle, a change would also be beneficial, but from what I have read at NASIOC forums and elsewhere, the Subaru manual transaxle is a bit tempermental about gear oil, and the shifting characteristics may change for the worse or better with an oil change.

[rao]

[quote name='IwannaSportSedan']" I was not aware of that" - Johnny Carson It always helps to confirm those sorts of things with people in the know... Anyone know if one could put a quaiffe helical gear torque-sensing LSD in the Legacy GT, Rear or Front? Would a 1 or 1.5 way LSD in the front cause more understeer, or degrade handling? Is it pretty much a moot point for the street/snow?[/quote] It is a bolt in job, but completely worthless for the street and very expensive. As far as all of the metal shavings floating around everyone's motor oil, transmission fluid and diff fluid, I think people are being paranoid. If there was truly a need to change all of these fluids so early, than the manufacturers would make that part of the service scehdule and people that didn't do this owould be experienceing lot sof failures. There is no harm in doing these services, but there is also no benefit. If you do change tranny fluid, make sure you get something of the rpoper grade GL-5 and remember that if you put synthetics which are NOT desigend for limited slip in the tranny the syncros will not work properly and you will not be happy (not becasue there is a limited slip in the tranny (there is, but itt is sealed, but because you don't want a fluid that is too slippery, which is what you also want if you have a clutch-type LSD, which the LEgaacy does not, but is what the fluid manufacturers are referrring to when they say LSD). Also, no one will ever convinece me that synthetic tranny fluid has ANY benefit over convetional fluid except for its performance in very cold temperatures (below 20 or so) for the first minute or so of operation. There, off my soapbox, for now :lol:

[IwannaSportSedan]

[quote name='rao'] It is a bolt in job, but completely worthless for the street and very expensive. If you do change tranny fluid, make sure you get something of the rpoper grade GL-5 and remember that if you put synthetics which are NOT desigend for limited slip in the tranny the syncros will not work properly and you will not be happy (not becasue there is a limited slip in the tranny (there is, but itt is sealed, but because you don't want a fluid that is too slippery, which is what you also want if you have a clutch-type LSD, which the LEgaacy does not, but is what the fluid manufacturers are referrring to when they say LSD). Also, no one will ever convince me that synthetic tranny fluid has ANY benefit over convetional fluid except for its performance in very cold temperatures (below 20 or so) for the first minute or so of operation. There, off my soapbox, for now :lol:[/quote] Good info, but that first sentence, does that apply to the front diff, or both Front and Rear? Our Miata has a Torsen LSD, which I really like. no ratcheting or lack of smoothness, no appreciable wear, and it works really well, especially with snow tires. I am just wondering if there is benefits or drawbacks of helical gear vs viscous type, but I think I l'll take that to the tech forum. BTW, in Iowa, for a couple of months a year, the high temperature is barely in the twenties. I have heard great things about Red-line synth gear oil and ATF, and seems like it would be a good upgrade, if it'll work, but otherwise I wouldn't get nuts about changing the driveline fluids before the recommended interval.

[rao]

You can get helical diffs all the way around, the Subaru uses off the shelf parts, not anything specialized. Might as well do the center and front as long as the tranny case will be apart. The synthetic tranny fluid is pretty neat in cold conditions.

[Salty]

I was told there is a break in oil in the Turbo, so maybe not the best idea to swap it out so early. I also would not bother with the diff oil, unless you really think you will own this car for 500,000 miles....even then I doubt there is any benefit. I also would not assume that because REdline works well in other trannies that it is the optimum lube for the Sube gearbox/diff. I put Castrol Synth in our 2.2Legacy and had a tranny failure about a year later due to the viscous coupling leaking internally. No idea what caused it. I have a feeling Subaru put products that deliver top levels of performance in our gearboxes. Just my .02 worth.