Best gearbox/front differential & rear differential oil to use on STI WR1?
 

Hi All,

WR1 is completely standard running around 320 bhp. This model has the 6 speed gearbox with DCCD.

Going to change gearbox/front differential & rear differential oil this weekend so looking to find out the combined capacity of both & the best oil for the job?

Capacity of the gearbox/front differential? I did this job on my old classic UK turbo & it took just under 4 litres. Am guessing the 6 speed box will have a larger capacity?

Capacity of rear differential? Again when I did my old classic it took about 0.7 litres, basically until it comes out the filler plug. Again I am thinking the rear differential might be larger to accommodate the larger gearbox?

What is the best oil I can use? I was going to use Millers CRX/LS 75w-90 NT competition fully synthetic in both the gearbox/front diff & rear diff. Then I spoke to Opie oils I was advised of the following.

Gearbox/front diff: First choice = Motul gear 300 75w-90 fully synthetic works best as the DCCD is a little bit fussy & Opie has had feedback from 1 in 20 people saying that the DCCD doesn’t work as well with the Millers product. Opie second choice would be the Millers. Stay away from Fuchs 5 as I in 5 people complain about DCCD problems :nono:


Rear diff:
First choice = Fuchs titan race gear 90 LS. Straight 90 weight mineral oil.
Second choice = Motul 90 PA. Again a straight 90 weight mineral oil.
Third choice = Millers CRX/LS 75w-90 NT competition fully synthetic.

Surprised at choices 1 & 2 on rear diff as they are mineral oils & also they don’t have the 75 weight for cold start protection. Tech as Opie said the 75 weight part of the blend is not as critical in the rear diff as it is in the gearbox & the 90 weight has cold start protection added to the blend.

Any advice & feedback on DCCD behaviour with the different oils would be much appreciated.

Cheers Paul :thumb:

Interesting.

I use the millers and actually use my DCCD in various positions unlike most road cars where it gets left in auto. Haven't gad any Dccd problems. Car is a sprint and hillclimb car, gearbox and diffs take some hammer, I don't hold back.

Speak to Alyn at AS Performance regarding oils

Just to clear it up. No one has reported issues with the Gear 300 to me, but a couple have said that their car hasn't got on well with the CRX. I deal with a fair few DCCD cars and the Gear 300 works brilliantly. On paper, the Fuchs Syn 5 should work well as it's a 75w-90 GL5, but for some reason, it doesn't get on that well with that box.

With the diff, the SAE 90 mineral oils work well, again there have been just a few that haven't thought the 75w-90 synthetic LS oils have worked that well in the diff, but that isn't just the Millers, that is all of the 75w-90 synthetics. To be honest, that could be people putting in the non-LS versions of the oil without realising and then blaming the oil.

Cheers

Tim

Thanks for info Joe. Do you happen to know if the rear diff on the wr1 is a limited slip diff or just a normal diff type?


Cheers Paul :thumb:

Thank you for your post Tim & the information provided earlier today. Be good to get a feel for the general consensus on this one as this forum obviously has a massive following.


Cheers Paul :thumb:

Just have a look on the last two pages of this thread

I also have an stock WR1 and changed the gearbox and diff oil this spring. I used the Motul Gear 300 75W90 for the gearbox and rear diff. No problems so far :thumb:

I used the Millers on my spec c hatch this spring; drive-in seemed noisier afterwards, more whine

I also used millers and mine seems a lot noisier , people recommend using that motul gear 300 , mine a 03 jdm sti

Thanks for all the info Gents, much appreciated.

Did a little bit more digging & here is what I have been advised.
The Millers CRX LS 75-90 NT - CFS is perfect for the rear diff as it is proper limited slip diff set up. However you shouldn’t use this product in the gear box, front & centre diff assembly as it can possibly mess with the synchromesh & ultimately in a worst case scenario lead to problematic gear changing.

The front & centre diffs are a type of LS diff but priority or compromise if you like has to be given to the synchromesh in the gearbox as that takes priority. The Motul gear 300 is not a limited slip spec oil but is a proven compromise for the front as it works very well with the 2 diff systems & the gearbox as it doesn’t contain the LS additive which messes with the gearbox Synchro’s. Also for the front the Millers75-90 NTCFS product, notice minus the (LS) limited slip additive also works very well.

Hence I will be running the Motul gear 300 in the front & the Millers with the LS additive in the back.

Thanks again for all the replies.

Cheers Paul.:thumb:

Thanks Joe, very sound advice indeed!!!


Cheers Paul :thumb:.

good luck getting the rear fill plug off if it was as stuck as mine :p jeez

:D Aye cheers Paul :thumb: