once and for all: is GL-5 bad for transmissions?

[Touchdown038]

Alright, I've been searching around and have found mixed reviews regarding GL-5 gear oil and Nissan transmissions. I've read that it can potentially eat away the syncros, but I've also read that it's fine.

Well I would like to clear this up once and for all: Is GL-5 gear oil bad for syncros?

What do the Nissan techs think?

[Fenvy]

gl5 in real diff is okay but not transmission

you hear about gl5 not good for transmission because the syncro are made out of brass and gl5 will eat away at it

you're proabbly thinking baout the redline gl75w90 in your rear diff? many people have that in theirs, I know I do.

[Touchdown038]

Actually I'm not thinking about Redline at all. I'm only wondering because I haven't found anything but GL-5 gear oil at any convenience auto stores (Schucks, NAPA) and I need some concrete evidence about this. (Technician's opinion counts as concrete evidence.)

[navysnail]

gl-5 or synthetic is bad for transmissions. gl-5 because of its corrosive properties, synthetic because it does not allow the synchronizers the friction they need to function properly

[s13sr20chris]

you have to look hard to find a gl4 oil. nissan manual trans fluid is gl4(and expensive). redline mt-90 is gl4 and not so expensive. also the redline is synthetic(i personally like synthetic m/t fluid). i use the mt-90 with great results. dont use redline gear oil for rear ends(gl5) or mtl(too light).

[navysnail]

i did read on redline's site that they put additives in their synthetic gear lube to make it ok for use in MT's,when i said that synthetic is bad, i ment it as a generic off the shelf synthetic

[Fenvy]

you have to look hard to find a gl4 oil. nissan manual trans fluid is gl4(and expensive). redline mt-90 is gl4 and not so expensive. also the redline is synthetic(i personally like synthetic m/t fluid). i use the mt-90 with great results. dont use redline gear oil for rear ends(gl5) or mtl(too light).

why not redline gear oil in rear diff? can you tel lme?

[navysnail]

redline has an additive to give it some friction to allow for synchro's to work. for the rear diff, use redline diff oil, it is slipperier so it lowers the friction

[Fenvy]

that 75w90 right? that's what I have in there

[NISTECH]

Gl5+manual trans=bad news

for the exect reasons mentioned,corrosive to brass syncros.

Sythetic gear oil +nissan manual trans= voided warranty.

Sythetic fluid as mentioned will cause a problem with gear braking between shifts due to syncro slipping. Nissan doesnt care if its redline or not, if its synthetic it doesnt belong in there.

IMO the only manual transmissions you need to worry about sythetic in is the ones with triple cone syncros [like in the Z33,L31,and B15 spec-v] Any of the older ones I think will do just fine with synthetic.

[s13sr20chris]

why not redline gear oil in rear diff? can you tel lme?

no no dude, not diff oil mad by redline in transmission. i use regular redline shockproof gear oil in the diff.

[hicas240sx]

what about the ones that say a bunch of GL #'s including 4 and 5?

[Fenvy]

oh? perhaps you meant something like "... rating that exceed GL-4 and GL-5"

it's still probably GL-5

[s13sr20chris]

yup

[oneline180]

i rem i used Redline Synthetic gear oil in my transmission and it was super crisp shifting, but i DIDnotice that the gears sometimes scratched when shifting harder than normal. So i switched to mobile one synthetic gear oil and there is a sloshy shift feeling, but the scratching has dissapeared.

[PalmerWMD]

Gl4 is the spec for Nissan MT's.GL5's have incompatible additives.

[s13sr20chris]

be carefull. mobil one gear oil is gl5.