Safe to put 75w90 is rear diff?

rv7 · 12-21-2006, 09:39 PM

It's time for me to change my tranny and diff fluids. I have read the "how-to" thread, which provided me with some good info; however, I am left wondering if it is ok to put regular old Valvoline 75w90 dino gear oil in the REAR diff. Some seem to have done so with no reported problems, and others swear that you need an oil with LSD agents (i.e. Subaru's LSD oil.) I guess I'd like to know what you guys are running in both the tranny/front diff as well as the rear diff. Thanks for the help.

HWYKING · 12-21-2006, 11:44 PM

you will be fine. try the neo synthetic 75w90. i went with this in my rear diff and tranny/front diff and the car feels smoother than when i drove it off the lot new. its not expensive either.

solbergfan · 12-22-2006, 08:01 AM

Simple answer-NO!!! There is a TSB regarding this issue from Subaru. Use only Subaru OEM fluid or Motul 90PA LS. The OEM oil is GL-S rated, not GL-5 or GL-4. Do a search, this topic has been covered many times.

http://www.bescaredracing.com/sti/ts...i_diff_oil.pdf

klaymon · 12-22-2006, 08:32 AM

Or just by this and you know you have the right thing.

https://www.subarugenuineparts.com/p...oducts_id=1063

STInk · 12-22-2006, 01:59 PM

No no no no NO!!!!!!

I used motul 300 with an additive. Recently I noticed my rear would get real wiggly in the rain. I felt like "What the heck happened to all that traction I remember?" I seriously almost looped the car a couple times. I drained the diff and replaced it with factory stuff and now it feels exactly like I remember - very planted, consistent, competent.

EricK · 12-22-2006, 03:25 PM

Quote:

Originally Posted by HWYKING

you will be fine. try the neo synthetic 75w90. i went with this in my rear diff and tranny/front diff and the car feels smoother than when i drove it off the lot new. its not expensive either.

Hope you enjoy that rear diff. while it lasts.Just a matter of time until you hear loud banging noises & the rear diff. binding.

***QuickSilverSTi*** · 12-22-2006, 03:59 PM

Motul PA 90. not/not 75w90. It's more than the additive - our rears need the higher rating of the oil. You don't have to just buy the factory stuff - there are actually synthetics made for our rears...not like it is the only one in the world ever that has that oil requirement...Motul PA 90 works great. I run German Castrol TAF-X in my trans and it's perfect. Don't understand why people refuse to believe something other than stock meets the requirements...

klaymon · 12-22-2006, 05:34 PM

Quote:

Originally Posted by QuickSilverSTi

Motul PA 90. not/not 75w90. It's more than the additive - our rears need the higher rating of the oil. You don't have to just buy the factory stuff - there are actually synthetics made for our rears...not like it is the only one in the world ever that has that oil requirement...Motul PA 90 works great. I run German Castrol TAF-X in my trans and it's perfect. Don't understand why people refuse to believe something other than stock meets the requirements...

The reason some of us don't like the aftermarket fluids is we've had trouble with them. For example, I used Motul 300 in my tranny. There are people here who will defend that fluid to the death saying it's the best fluid for the tranny and they've never had trouble. I had nothing but trouble with it. I use OEM fluids in the drivetrain because I know they work and that's what the manufacturer recommends. We're not discrediting your experience with a certain product, but don't make it sound like it's God's gift to the car either. There are mixed results in the real world...

HWYKING · 12-23-2006, 01:28 AM

Quote:

Originally Posted by EricK

Hope you enjoy that rear diff. while it lasts.Just a matter of time until you hear loud banging noises & the rear diff. binding.

you know what im going to check with neo again, i spoke with them directly and they told me that i would be fine. if you guys say i should change it then i will. thanks for the correction fellas.

EricK · 12-23-2006, 06:39 AM

Quote:

Originally Posted by HWYKING

you know what im going to check with neo again, i spoke with them directly and they told me that i would be fine. if you guys say i should change it then i will. thanks for the correction fellas.

Didnt mean to be a jerk but I would hate to see something happen to the diff with it under warranty & get it denied cause it has something besides the stated Subaru fluid inside.Seen it happen at work with Acura MDX rear diffs.

HWYKING · 12-23-2006, 11:28 PM

Quote:

Originally Posted by EricK

Didnt mean to be a jerk but I would hate to see something happen to the diff with it under warranty & get it denied cause it has something besides the stated Subaru fluid inside.Seen it happen at work with Acura MDX rear diffs.

its all good, im done crying now. jk no i would prefer to know what is the correct fluids to be used in our cars. i emailed neo and will wait to hear back from then, plus it has been 10k since i did the fluid change so i will again use the synthetic for the transmission, but pick up the factory lsd 90wt tuesday and see if i hear/feel the difference. thanks again erick

12-21-2006, 09:39 PM	#1
rv7 Professional STI Racer Posts: 639 IWSTI Addict since: Sep 2004 Trader Rating: (7)	Safe to put 75w90 is rear diff? It's time for me to change my tranny and diff fluids. I have read the "how-to" thread, which provided me with some good info; however, I am left wondering if it is ok to put regular old Valvoline 75w90 dino gear oil in the REAR diff. Some seem to have done so with no reported problems, and others swear that you need an oil with LSD agents (i.e. Subaru's LSD oil.) I guess I'd like to know what you guys are running in both the tranny/front diff as well as the rear diff. Thanks for the help. This ad is not endorsed by this member. Please register or login to hide this ad.

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12-21-2006, 11:44 PM	#2
HWYKING Senior STI Driver Car: 06 SGM STI Fav Mod: CUSCO 1.5 RS lsd Location: Southern Kalifonia Posts: 390 IWSTI Addict since: Nov 2005 Trader Rating: (4)	you will be fine. try the neo synthetic 75w90. i went with this in my rear diff and tranny/front diff and the car feels smoother than when i drove it off the lot new. its not expensive either.

12-22-2006, 08:01 AM	#3
solbergfan Senior STI Driver Car: 05 CGM STi Location: Southeastern PA Posts: 355 IWSTI Addict since: Jun 2005 Trader Rating: (0)	Simple answer-NO!!! There is a TSB regarding this issue from Subaru. Use only Subaru OEM fluid or Motul 90PA LS. The OEM oil is GL-S rated, not GL-5 or GL-4. Do a search, this topic has been covered many times. http://www.bescaredracing.com/sti/ts...i_diff_oil.pdf

12-22-2006, 08:32 AM	#4
klaymon S204 Racer Posts: 3,075 IWSTI Addict since: Jul 2004 Trader Rating: (1)	Or just by this and you know you have the right thing. https://www.subarugenuineparts.com/p...oducts_id=1063

12-22-2006, 01:59 PM	#5
STInk STI Driver Posts: 228 IWSTI Addict since: Apr 2004 Trader Rating: (1)	No no no no NO!!!!!! I used motul 300 with an additive. Recently I noticed my rear would get real wiggly in the rain. I felt like "What the heck happened to all that traction I remember?" I seriously almost looped the car a couple times. I drained the diff and replaced it with factory stuff and now it feels exactly like I remember - very planted, consistent, competent.

12-22-2006, 03:59 PM	#7
*QuickSilverSTi* nulla poena sine lege Car: '08 GT500 Location: Northern VA Posts: 1,768 IWSTI Addict since: Nov 2003 Trader Rating: (5)	Motul PA 90. not/not 75w90. It's more than the additive - our rears need the higher rating of the oil. You don't have to just buy the factory stuff - there are actually synthetics made for our rears...not like it is the only one in the world ever that has that oil requirement...Motul PA 90 works great. I run German Castrol TAF-X in my trans and it's perfect. Don't understand why people refuse to believe something other than stock meets the requirements...