Oil to use in 6 spd gearbox and rear diff?

[teK--]

when i had the car at making about 35% increase in power ATW, i found that with 300V in the box, shifting from 3rd to 4th, the syncros don't come together nicely. went back to the stock subie box oil. box works perfectly...

Which stock oil you referring to; Multitrax?

[overl0ad]

no idea what oil...

i went to STi and got them to do it.

i don't think it's the syncros. cos the issue only came up when i used the motul, and went away immediately after i swapped back to the OEM oil.

i've heard that the 6 speed box is a little "see which one you get". some of them are bomb proof, some didn't get the syncros lined up perfectly at factory.

best description i've heard so far is

"half of them are built by highly qualified mechanics who love what they do, the other is built by monkeys, so it depends on your luck"

[PAZ04U]

I still need to do my 50k service. Just noticed motul gear 300 is a bit expensive ie $40 per litre. Wondering other options out there. Just to mention I don't know if this happens to anyone else but it pops out of first slightly rarely when I go to shift to second. It happens when I grab hold on the shifter sort of thing. I'd like to try and fix this with the new oil I put in.

Thanks, Alex.

[Robbks]

I'm running Hi-Tec SynGear recommended to me by my mechaniic
very happy with it's performance both hot and cold.

I've had the jumping out of first gear issue happen on friday night
but i did sidestep the clutch at 5000rpm on dry bitumen

I also like Castrol EPX 80W-90 for the rear diff too.

[3rspecb]

Subaru docklands STi service centre use Castrol Syntrax gear oil in the STI gearboxes. Thats what I'm using and have had no issues with its cold or hot performance. I've done a few track days using syntrax gear oil and it held up fine.

[Stu]

Just to add my 2c.

Running Motul Gear 300 in the 6 spd and Castrol Multitrax in the diff. No problems so far and shifting is fine. Kinda thinking I shoulda used Syntrax in the rear though... just couldn't find any in Canberra at the time.

[MY02B4]

Interesting thread. Where is the best place in Melbourne to get Motul/Redline gear oil? I used Redline in my B4 and changing gears was very smooth. I find it difficult in the 6spd to go from 3rd to 2nd without really revving it or slowing right down. Anyone else experience the same? I'm hoping good gear oil will help.

[PAZ04U]

I'm thinking about using the redline light weight shock proof in the gear box now and a redline ear oil in the diff. Not sure which redline gear oil to use in the diff though?

Can anyone help me out here that has used the redline gear oil in the diff and tell me exactly which one they've used with exact weights etc.

I thought we had to use 75w90 in the gearbox but it looks like the redline lightweight shockproof is 75w80? Will that be ok?

Anyway any feedback will be great. Thanks, Alex.

[Robbks]

my gearbox builder advised against using redline in my box '06 6speed
as he believes it can cause issues with synchro's/ shift-forks, etc.

he has a good reputation around Hobart and has built and maintained boxes for serious motorsport (ARC, Targa) and street cars for lots of years.

Also, it's a waste of money IMHO.
use decent oil and change it often.
if you don't change oil often, all the microscopic metal parts that wear off begin to impregnate the bearings etc and wear out other parts much faster.

[MY02B4]

I've noticed it is almost impossible to downshift from 3rd into 2nd gear when it's cold but it's ok when it's warmed up. My initial thought was that the previous owner/mechanic must have put in a cheapo gear oil but when I spoke to my mechanic, he reckons it's the synchros and not the oil especially when it's easy going from 1st up to 2nd but not 3rd down to 2nd. His suggestion was to use a thinner oil but of course that means more wear on the synchros so I'm going try using the recommended Syntrax and see how it goes. I'm sure hoping it's the oil and not the synchros!

[Robbks]

just do a quick test mate.
drain the old oil
grab 5L of the cheapest/ thinnest junk mineral GB oil you can (ATF also works as it's nice and thin)
refill box with the oil (only use about 3.5L) and take it for a sedate drive around the block a few times to get it up to operating temp
shifting in and out of each gear frequently so that all synchro's and gears get a good workout (at low load)

drain the junk oil when it's cooled a little and keep pouring in the leftover litre or so (helps to flush anything else out of the box)

then grab 5L of multitrax, pour in 1/2 a litre or so with the drain bung out so that is flushes the rest of the junk oil out.
the refill the box with the remaining multitrax and a tube of Nulon G70

then see what the box feels like.

this way will only cost you ~$50 as opposed to over $100
and you will have completely flushed any remaining junk out of the box.
your synchro problem may have gotten a little better.
if not, you know for sure that it is definitely a synchro issue,

[MY02B4]

I got my mechanic to do everything as I don't have that much time to spend on the car so I took a punt and asked him to do the syntax plus G70. Unfortunately it was still difficult to go from 3rd to 2nd when it was cold this morning so looks like I will meed to get it looked at by a reputable workshop. I don't drive it that often so I might just leave it for now and take it easy when its cold.