Box is an 80k miler on an old 93 WRX and being as I'd had her 30k miles I thought I'd treat it to fresh trans and diff oil from the helpful chaps at Opie.

On the old oil I used to beat the synchros into 2nd very occasionally with a real tug on the lever, after the change it now crunches into every gear except 4th unless I take an age when changing.

Why have the synchros stopped working with the new oil? The specs seem ok, fully synth 75W/90? Theres 4 litres in the box, just under a litre in the diff, no leaks, 2000 miles on the new stuff and the levels are all good.

I've got no idea what the old stuff that worked better in the box was, anyone else had this/got any ideas?

Many thanks

Andy

 

Some poeple have put the Silkolene in and been fine, others like yourself have had troubles. Seems in these cases a semi-synth works better such as Castrol Syntrax (or whatever its called now).

Tony.

 

I tried Syn-5 in the box of my 99my when I had it and got crunching from 4th to 5th above 4k Drained it and replaced it with Castrol Syntrax (Now called Driveline) and this cured the problem. It's not that Syn 5 is dodgy, it's just that it's too slippy for the synchro! Some people have the problem and some don't. I put the Syn5 into the box in the wifes Primera where it works fine!
JohnD

 

i have to say i thought that the redline Lightweight shockproof i had before was better than the silkoline i have in there now.....the box feels much looser..

 

Nuts. I was gonna buy Syntrax originally but got advised to buy the dearer stuff by the guy at Opie. Thats cost me. Cheers guys, guess I'll be ordering some Syntrax ASAP then. I'm still cringing at the noises from the video going round the ring. Hope it hasn't damaged the box, I'll see if any new metal is clinging to the magnetic plug.

 

There was a long thread to which Oilman contributed on here some while ago about this very subject. As he sells the product obviously he was pushing its benefits, which is fair enough, however some of us have had less than satisfactory results from its use. The oil is excellent - but not always in a Subaru box!
If you get Driveline (Syntrax) get it straight from Castrol www.castrolclassicoils.co.uk
JohnD

 

Double bollox. Castrol Classic Oils is in the next village from me as well

 

There are many people on here using Silktran Syn 5 75w-90 with no problems at all.

Spec wise it's a 75w-90 gear and diff oil which meets GL4/GL5 specs. The Castrol Syntrax is also a 75w-90 gear oil meeting GL3/GL4/GL5.

The only difference is that the Silkolene is a fully synthetic and the Castrol a "part-synthetic" as they term it.

I can only assume that the "older" boxes don't like it due to the fact that it uses no petroleum basestocks.

Semi-synthetic or part-synthetic is fine but if there is more power through the box than stock or you are doing trackdays then semi or part will lose viscosity too quickly and will not necessarily be up to the job.

There is nothing wrong with the quality of the oil, we use it in 1000bhp cars however there does seem to be some quirky element with the synchros here that doesn't like very high quality oils.

Has anyone here experienced this with Motul Gear 300 75w-90?

Cheers
Simon

 

I guess its an older box issue then, although JohnD had it on an MY99?

Fair play to Simon, hes offered to refund me for the oil, I'll report back what happens when I put semi-synth in.

Im running stock power, well less than 300 bhp anyways, and avoid clutch dropping starts etc.

 

I've asked Silkolene to comment on whether there is a logical explanation and will post the reply here but this is the first time that we have experienced this on an Impreza and I'd like to get to the bottom of the problem from an oil perspective.

If it turns out that synthetics are better for synchros then it must be an addative issue, we'll see.

Cheers
Simon

 

Top Marks for Opie. Simon has not only refunded me but is sending me the semi synth to try FoC. Dont think I've ever had customer service like that. Will report back on the oil change when its done.

 

Silkolene silktran syn5 worked wonders for my MY95 box, Almost totally elliminated the crunching. Some strange quirks, have these Subarus !

 

It is a known thing with this and many other fully synthetic gearbox oils, I first experienced the effects (using the Sylkolene although as mentioned others are the same) back in 1999, quickly reverted to Shell semisynth and all was fine. The Subaru syncros don't always seem to bite properly when a fully synth is used.

Definately a gearbox design issue but, as mentioned, not something new and not consistent.

bob

 

Bob - have you tried a full syn. in the 6-speed box? If so, what were your findings?
JohnD

 

I always found after first changing the oil that the gearbox can be a bit uncoperative with the 1st and 2nd syncros for the first 100 or so miles, after that it seems fine. But thats with using Castrol Syntrax.

 

Yes I have John, it was "not bad" but the Castrol was better, in between I made a big mistake and put in some Redline Heavyweight shockproof, box nearly seized when cold, could hardly move the gear shift. Took three changes to finally get rid of the Redline.

bob

 

An oddity indeed and seems inconsistant. I wonder if the condition of the synchros play a part in the results.

Anyway, here is Silkolene's answer.

Quote:

Yes, it could be ‘more slippery’; a more ‘commodity’ grade 75W/90 may be better. Even more likely is that the Syn 5 is higher viscosity. The trouble with SAE ratings is that they’re a mile wide! If the transmission runs fairly cool, the higher viscosity could be reducing synchro cone friction.

Unquote:

Cheers
Simon

 

Oil Change done; crunching has gone; synchros seemed to be operating normally again. Thanks again to Opie for sorting the problem out.

Andy

 

Thanks Andy for letting me know.

I suppose the next question here will be what did you use?

For those that are interested, this:

http://www.opieoils.co.uk/TechSpecs/...5W-90_3170.pdf

Thanks again for the feedback, much appreciated

Cheers
Simon

 

Oh dear. Here I go again.
I've got a transmission oil change coming up.
99 UK Turbowagon. Only 34K miles.
Last two changes I've used Amsoil Series 2000 75/90. Very expensive and called fully synthetic but as oilman has said before Amsoil don't release details.
Now I've had no problems with this oil but was thinking of changing to Silkolene as I use that in engine.
Now I'm not sure what to do.
I must suffer from SPS.
Scooby Paranoia Syndrome.

 

The car in question was a '93 with many more miles on the clock, I can only attribute the problem to worn synchros, there is no other logic.

At 34,000 I can't see a problem with Syn 5.

Cheers
Simon

 

Just to let you know that the above was at around 10k

JohnD

 

Thanks!
So the lottery that seems to be Scooby lubrication continues.