Just thought I'd post my recent experiences with gearbox oil in my JDM STI 2. When I got it, not knowing anything about it's servicing history in Japan I thought I'd do some basic servicing including changing the gearbox oil. I did my research and found the correct spec (GL 5, SAE 75 - 90) and narrowed it down to two choices, Silkolene Silktran Syn 5 (fully-syntectic) or Castrol Syntrax (semi-synthetic).

Some people around have said that the Silkolene can make some gearboxes noiser and crunch (especially the older ones), but since they were both the right spec I thoght I'd put faith in technology and go for the fully syntetic. Instantly it was noiser, I could syn the synchomesh whine as and I changed gear, especially first and second. So, I thought that it really wasn't acceptable, (although it was better on the colder mornings we're having now, which leads me to think it's just plain too thin) and sourced some Castrol Syntax. Put that it in today and it's instantly extremely quiet and slips into all gears completely silkily. I'm especially impressed with how much different it is going from neutral to first when at a stand still.

The other thing is that the amount of metal shards on the magnetic sump plug were more in the few weeks I had Silktran (even though the oil still looked almost new) than when I first let the black gunk out that it had when it was imported.

Use Castrol Syntrax!

John

 

for synth oils use either Motul or Millers CRX..............

 

I have motul 300v in the engine. No complaints about that.

 

I've used syntrax in six of my Imprezas, no probs.

Have been using silkolene in this one, and broke the bearbox slightly. I very much doubt its anything to do with the fluid though, more the power its having to cope with.

Both are quality fluids- whilst silkolene etc may have a very slight edge, Syntrax will do the job just fine, and both are in a different league from the usual garage stuff.

 

i have use redline light weight shockproof gear oil

 

Syntrax has sorted synchro/gear crunch in 2 of my 3 Impreza's
which reminds me, the 3rd must be due 4 litres.

 

thanks for the advice daytona2222 got to change gear oil on my 04 wrx to try and cure difficult selection,i would have gone down the fully synthetic route if i had not read your post last thing i need is to make gear operation worse so gonna use the semi synthetic and hope it cures the problem