MOTUL vs NEO Synthetics?

[ZER026D]

I am looking for the best tranny oil for my car since Mobil1 is making me grind gears. The best I can find is NEO and MOTUL so who is is better I dont want to spend that much for oil then say I wish I went with the other one.

[sperry]

Originally Posted by ZER026D

I am looking for the best tranny oil for my car since Mobil1 is making me grind gears. The best I can find is NEO and MOTUL so who is is better I dont want to spend that much for oil then say I wish I went with the other one.

I'm running 3/4 RedLine Lightweight Shockproof Gear oil and 1/4 RedLine 90w75ns. Seems to work fine!

[ZER026D]

I hear that redline will cause problems.

[dknv]

what's the reasoning behind that formula?

[sperry]

Originally Posted by dknv

what's the reasoning behind that formula?

I tried straight 75w90ns in the tranny and 75w90 in the rear diff. The 75w90ns doesn't have enought friction for the synchros, so while it's great for the bearings in the tranny, the synchros tend to slip too much, requiring very gently operation of the shifter to keep it from grinding. (I can only assume this is what Evan's refering too since he didn't mention what "problems" RedLine causes.)

The shockproof has a different friction modifier, and it's designed for racing transmissions. It has this crazy high surface tension (that stuff won't even drain into my oil catch pan when I last did my fluid swap, I had to push it inot the drain with a towel!!) that prevents the oil from foaming in the transmission, and leaves a nice heavy protective coating on the gears. After trying the 75w90ns and hating it, I tried pure Lightweight Shockproof. The difference was night and day! The synchros grab reliably, and a lot of the notchynes went away, making it much easier to shift. However after reading that the Lightweight shockproof isn't necessarily the best on the bearings, I decided to try what a lot of other people have done, and homebrew up a RedLine cocktail.

Lots of people say to use 3/4 RedLine 75w90ns and 1/4 Heavyweight ShockProof. However, Summit was out of Heavyweight when I was there last, and since I really like the pure Lightweight, I figured I'd try the 3/4 Lightweight ShockProof 1/4 75w90ns mixture. Bascially I want to lighten up the oil a bit for bearing life, but I don't want to lose the great feeling synchros/protection the pure Shockproof gave me. Next time, I may try a 50/50 mixture... or if Summit has the Heavyweight, I'll try the other mix.

As far as tranny protection, when I recently swapped the fluid at 30k miles, there was less "sludge" on the magnet from the last 25k miles than there was when I originally swapped fluids at 5k miles. So I figure that stuff's gotta be doing a pretty good job.

FYI: RedLine makes an "UltraLightweight ShockProof" gear oil... that may be a good non-mixed solution, but I've yet to see it at Summit.

[ZER026D]

Ok I put in the Redline mix and no more grind thanks scott i am going to email Mobil1 right now.

[sperry]

Originally Posted by ZER026D

Ok I put in the Redline mix and no more grind thanks scott i am going to email Mobil1 right now.

Sweet dude! Glad it works... let me know if you run into any problems... I've run the shockproof in min for over 20k miles nad haven't seen any issues, but this is all still kinda experimental.

[ZER026D]

here is what i got back from Mobil1

Mobil1 Synthetic Gear Lubricant 75W90 is rated GL-5 and most manual transmissions require a GL-4 specification therefore should not be used.

and the person that told me to use it ?
http://www.scoobymods.com/forums/sho...&threadid=1743

Thats lame that they would recomend that and the fact that it took me this long to get an answer from a few dirfront subaru techs.

[ArthurS]

Hmmm.....maybe someone should post that on that link....

I still have not replaced my tranny fluid myself. I had a guy do it at 7k, and now I am at 20k. When should I do it next? Just wait for the 30k service?