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Transmission Fluid & Rear Diff Fluid?

37K views 14 replies 11 participants last post by  tight-si 
#1 ·
I've hit 36000 in the WRX and I want to change the tranny fluid and diffrerential fluid. I've looked on that Cobb site with all the oils. I was lookin at gettin Redline MT90 but I read thats its only a GL-4 and Subaru reccomends GL-5.

So what would be a good Transmission fluid, and rear differential fluid? Can I use the same oils for both. And what are the capacitys, for each. Thanks.
 
#2 ·
Well I'll just say that I'm using Redline 75w90NS and I don't like it at all. I have more grinding since changing over. I've also heard the same thing from many others. I've also heard that the Shockproof HD is good and the regular 75w90 should be good for the diff. As for the quantity, don't quote me on this but I think it's ~4.5 quarts for the tranny and ~.5-.75 quarts for the diff. It should have it listed in your manual.
 
#4 ·
Transmission
Manual
Type: GL-5
Capacity: 3.7 quarts
Weight:
75W-90 (all temperatures)
80W (86 F and colder)
85W (-22 F and hotter)
90 (32 F and hotter)

Automatic
Type: DEXRON III*
Capacity: 9.8 quarts

Differential
Type: GL-5

Rear
Capacity: 0.8 quarts
Weight:
75W-90 (all temperatures)
80W (86 F and colder)
85W (-22 F and hotter)
90 (32 F and hotter)

Front (Automatic Transmission)
Capacity: 1.2 to 1.4 quarts
Weight:
80W-90 (all temperatures)
80W (86 F and colder)
85W (-22 F and hotter)
90 (32 F and hotter)
 
#5 ·
As for the tranny, many many people have had good experiences with the Redline Shockproof of any kind. Helped a TON on my wagon. I also tried either the 75w90NS or the MT90, don't remember which one, but it was a complete waste of money. About $80 in oil that I changed out in under two weeks for the Shockproof. :sadwave:
 
#6 · (Edited)
tell me about shockproof - i'm about due for a change. is it really thick? does it help smooth out the notchiness? and, does it gum up really bad in cold winters? also do you all use it just in the trans, or in the diff as well?
 
#7 ·
It didn't seem excessively thick, and was fine in our Wisconsin winters. I put it in the diff as well, but off the top of my head I don't remember if that was deemed okay for it or not from Subaru specs. On Redlines website, they seem to recommend this as more of a diff oil than a tranny oil. I put it in both and had no problems. And yes, it did indeed smooth out the notchiness for me quite a bit.

http://www.redlineoil.com/products_gearlubricants.asp?pvID=86&prodID=61&subcatID=20
 
#8 ·
Shockproof's description through that link says:

A unique gear oil designed to lubricate racing transmissions and transaxles which see serious loads (not recommended for most syncro-type transmissions).
How has the Shockproof performed for you so far?
 
#9 ·
I had no problems back when I still had my wagon, and a few other people on this and other boards have had good experiences as well. Chances are, I'm going to put it into my rs now as well.
 
#10 ·
yo vanilla said:
tell me about shockproof - i'm about due for a change. is it really thick? does it help smooth out the notchiness? and, does it gum up really bad in cold winters? also do you all use it just in the trans, or in the diff as well?
It's actually quite thin - the idea is that it's got a low viscosity to cut friction but builds a super thick and heavy duty film between surfaces. Doesn't gum up at all. Does not carry a GL rating. Redline figures it'd exceed GL-5 but they have different intentions for it and so just don't rate it at all. So technically, it's the wrong stuff. In reality, it seems to work quite well.
 
#11 ·
I put Redline MT-90 in my '03 WRX wagon at 18000 miles and it's been great (I'm at 27k now). I used Mobil-1 full synthetic gear oil for the rear diff.

You know those synchro-type transmissions that Redline does not recommmend Shockproof for... that's us.

B
 
#12 ·
I had changed to Mobil 1 in the tranny at 15k. It was noticeably smoother at first, but seemed to go back to being notchy after 5,000 miles or so. At 30k I just switched to Amsoil 75w90 full synthetic. Man, what a difference! The trans is so much smoother than it ever has been. It doesn't feel as notchy as before and I can actually downshift into 1st gear without double clutching.
 
#13 ·
BG Products anyone??

Has anyone ever used BG Products before? I have in past vehicles and have had excellent results with their products. I'm looking at replacing my tranny fluid and rear diff fluid in my 2002 WRX with the BG Ultra-Guard Synthetic fluid they make. You can read about it here: http://www.bgprod.com/bgprofessional/bgproducts/dline.html
Just scroll down a bit - it's towards the top part of that page. 75w90 Gl-5 fluid synthetic
 
#15 ·
Hot_Dog said:
They also have something called Synchroshift, that may work too, although it doesn't say its GL-5. Give the Ultra-Guard a shot...the worst that happens is you have to drain it out and put something else in.

Yes, the Synchroshift is what I have used in the past on some Honda's I have owned. Works awesome - smoothes out rough shifts great. I'm going to ask my local rep what he would recommend and what the actual specs are on the synchroshift fluid.
 
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