What Gear lube to use in Differentials,transfer and transmission

[billsmartis]

I read on a post not to long ago that Synthetic GL5 75W-140 for diffs and Synthetic GL5 75W-90 for Manual Transmission and transfer case. My Haynes book says GL5 75W-90 for both but on several posts I read they say GL4 for trans and diff. Can any body remember the post that mentioned the first sentence and where it is. I going to put the 75W-140 in the diffs but need to know about the GL4 on the trans and Transfer case
Bill S

[obradleyo]

there is a great post like two weeks old about this same topic it will explain every thing.

[jtgh]

GL5 is for axles. origioally it was for these high load gears called Hypoid gear sets.
noted for there high pressure and loads.
the additive in GL5 was notorious for eating syncros.

most modern top of the line gl5 , says on the bottle or somewhere on there complex web sites. Ok for syncros.?

ALL GL 4 is good for the tranny and xfrcase.

the tranny has way less load factor. tons less. no pun.

so ,if you put GL5 in an GL4 box (fsm says GL4) then it is over kill. if it is safe for syncros. (how is that for concise)

why every bottle of GL5 not say that, is anywonder.

Just run any top brand of gear lube , and change often , 20k? and not 100k.
syn, is ok and gets dirty just as fast.
changing it , is the only way to get it clean.

[billsmartis]

jtgh,

What I have is Quaker State SAE 75W-90 Full Synthetic Gear & Differential Lube. I read on 1 post their using it with no problems. But to play it safe maybe I have to call Quaker State to confirm it.

Bill S.

[jtgh]

is see posts all over . QS web site useless , looks like Diet Coke seller.
one in 2002 that said. ( up to 2008 )

Quaker state 75w 90 synthetic , says right on bottle ,safe for bronze syncros.
and
does not us the EP (extreme pressure) sulfpur Phosporous. but some thing else.

quotes contra dict
the Quaker State Tech at that time informed me that their GL-5 was not Yellow Metal Friendly. Perhaps their formula has changed.

diff LUBE in USA and CANADA. same name on bottle ,fine print diffr.


after all what do we know.
the manual and fsm says dont use it.
we do know the EP sulfur Phos. is bad for most yellow metal alloy syncros. (not all)
those are the facts. every one knows it and many oil makers have comments on their respective web sites about it.

some EP addative can eat them.
so.
i behoves the bottle makers to mark the bottles. or have a web page.

read the fine print.

see this
manual transmission oil? - Car Forums and Automotive Chat

common thread ,all forums, little answers from the dino joice guys.
(if not on label GL5 , ok for syncro)

[jtgh]

btw, the damage happens real slow, so dont say,
gee, been runing it all year nad syncros didnt melt.

worst case is cars that sit , i hear.

[billsmartis]

jtgh,

Is it ok to put GL5 in the transfer case ? Is there any brass or copper metal in the transfer case ?

Bill S.

[jtgh]

ill look inside my spare.

i dont know.

all I know is what the book says GL4. for factory recommended Lube type.

i would guess GL5 is ok in the xfr case. but i dont know.
if the stupid oil makers would state. (Marketing ppl are wierd for sure)

"Safe for all GL4 applications. but no, that would be too easy , too clear)

why dont you just by the lube, on the shelf that says that.

I wonder ? whY?

many brands are labled, Syncro Lube. or to words that say the same.

buy GL4
Buy GL4/5 bottled lube
buy GL5 , marked Synco lube.
buy GL5 , marked safe for syncos.

others pass.

that is my best shot.

or dig thru 100 oil company web sites. ouch.

the oil makers should know they are selling lube for older cars. gee , they need it.
so why they cant , align they labels to the printed FSM and operator guides is a wonder.

lawyers, clueless, inept? gawd knows.

wish you the best and for your car.

[billsmartis]

I called Quaker State manufacturer which is owned by Shell oil and was told SAE 75W-90 GL5 synthetic Gear and differential will attack bronze,brass & copper and not to use it in manual transmissions. You need to use their GL4 lube in this application.

Bill S.

[jtgh]

they said the same thing in 2002.
so 7 years later same.

and note, still no mention on the label. but it did say GL5 only.

so , this example proves my list in post 8.

nice of them to make it so hard.


It has the EP additive in it that eats syncro's. Sulfur Phosphorous. to bad it can be on label to , this chem .name.

it takes a long time. so ignore all the posts that say , hey , i ran it for 1 year, and had no problem.