My 2004 WRX STi has a rear limited slip unit within the axle. I recently swapped the original 38,000 mile rear axle fluid out for some Castrol Syntrax 75W90 fluid.

Within a few miles I noticed a bit of a binding sensation...after 3000 miles, I can definitely feel the rear bind especially during WOT slides on dry pavement

I'm guessing I need a limited slip additive or a more appropriate oil with some slippery stuff in it.

Any recommendations?

Thanks for the assistance.

 

Use Motul 90PA

 

Thanks!

 

Swapped the Motul 90 PA in about a month ago and it appears the axle liked it!

Appreciate the assistance.

Thanks

 

I had a similar problem when I chaged the gearbox oil on my spec C. Gearchange was improved but diff grabbed when used hard. I spoke to Castrol technical who confirmed that Syntrax has no lsd additive. I put some in and all was well.

 

Dedicated LSD Oils are required or a 75w-90 that is suitable for LSD's.

http://www.opieoils.co.uk/TechSpecs/...90_PA_3181.pdf

http://www.opieoils.co.uk/TechSpecs/...04%20wheel.pdf

http://www.opieoils.co.uk/TechSpecs/...04%20Wheel.pdf

Cheers
Simon

 

None of those links appear to be working...

 

Ahh,

That is becuase they are transferring data to our new site.

Should be back up and running by the morning.

Cheers

Simon.

 

Sorry but disagree, your rear differential is Suretrac (or is your car JDM model?) thus any conventional differential 80W/90 or 75W/90 oil is fine.
I also have Suretrac rear differential fitted in my MY03 WRX and works fine with both Syntrax or Motul Gear 300 oils.
Except your rear diff is plated like last revisions 6MT DCCD's from MY05-06 cars.
JIM