Gearbox/ Diff Oil, "98 Forester

I find it far easier to have the workshop do it! They have the special gun to get the oil in via the gearbox dipstick tube ...

Our mechanic of some 20 years informed me that Subaru and Honda gearboxes do not like fully synthetic oil. He uses semi-synthetic. That's what I had put in Roo2's gearbox when I had the oil changed a couple of years ago. It works the same as it always has.
 
That ended up being a quick and easy job! Longest two bits were confirming that i was looking at the gearbox drain plug and then driving to supercheap for a 21mm socket. Taking the air filter box out was a massive help... id never seen the gearbox dipstick before. Added nulon G70 to the gearbox, will see how it goes. 15km test afterward and things are feeling really good! Psyched to have a successful first solo mission under the car.
 
It's well hidden. Much easier to get at on my 93 Impreza! Glad it went well.
 
timbercomp said:
Sorry for the huge thread-dig here, but can anyone point me at a useful vid online (or doc to follow) to do the gearbox and diff oil changes on a 2.0L NA 5sp? I see a few around but wonder if anyone has found something especially helpful
Click to expand...

dunno if there's a vid around, but its not rocket surgery.


  1. Big plug on the bottom of the gearbox. Hard to miss, there's only one. Tool you need depends on the year (older are a big bolt like the engine sump plug, newer may be hex or square socket).
  2. Pull the plug, let the insides dribble out (probably smell like sulpher if the usual Castrol stuff has been used).
  3. Clean fine metal particles off plug. Hope there's not too much. Large chunks indicate badness (chipped gear tooth or similar).
  4. replace plug. Use new washer or a smear of RTV suitable for oil.
  5. fill with listed amount of new oil through the dipstick (3.5 litres for single range, 4 for dual). A funnel and small piece of plastic tubing is handy here. You'll probably want to remove your air filter box to get better access.
  6. Check fluid level.


Diff.

  1. There are two plugs, top and bottom, both facing rear of vehicle.
  2. Use a 1/2" socket driver to remove both. Catch dribbles.
  3. replace lower plug (again, a smear of RTV on the threads won't hurt)
  4. Fill through upper hole until its full (A big syringe is handy here. You need something to be able to pump oil in from below, as you can't pour it in due to space constraints). about 0.8l (probably less due to residual old oil remaining in diff).
  5. Replace upper plug.
For oil -- use as recommended above. Penrite full synth made a big difference for me over the Castrol (was VMX I think, now called 'universal' gear oil). anything around 85W90 is ok for our conditions. The penrite pro-gear synthetic is 75W90, which may be what contributes to better cold shifting..



Oil must be GL-5 to handle the hypoid gears in both the gearbox and diff.
 
^^^^^ yes!! All straightforward, the main thing slowing me down and planting seeds of doubt was that I'd never seen a transmission in my life. Now that hurdle has been cleared, the sky is the limit!
 
I recommend using a diff plug tool not the 1/2" drive on a breaker bar. This is 12.5mm & the plug is 13mm, doesn't sound like much but these are often seized on & using the wrong size just damages the plug. Pretty cheap from eBay:

8/13MM SQ plug tool | eBay
 
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