Safe for Yellow Metals GL-5

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cobrasneat

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Central Florida
My 91 Wrangler manual 6cyl (new to me) is kicking out of reverse gear. Before taking it apart, i want to change the fluid and see how much metal there is and what condition it's in (again, new to me). My first YJ and the first time I had a GL-5 75w-90 fluid recommended with "Safe for Yellow Metals" (i.e., usual GL-4 for toyota parts). My beach town has nothing in stock that is GL-5 but also states specifically its safe for yellow.

1. Any recommendations online on where to buy? if not GL-5, will GL-4 suffice?
2. Gear kick-out - if fluid change doesn't work, other ideas? the clutch does not seem to be sticking or not pulling all the way out.

Thank you.

NSB

Wrangler Man Trans Fluid Reco.jpg
 
The manual is wrong. It was supposed to say GL-4.

Jeep also says you can use 10W-30 synthetic oil now.

Personally I have used Red Line GL-4 and am now using syn 0W-40 in it and I can't tell any difference in the two.
 
Manual should have said GL3 back then which would be superseded to GL4 later on. GL5 was always a misprint. There are some “safe for yellow metal” GL5s but they still have more sulfur than GL4 and don’t work as well in a manual. I am using Driven 80W-90 GL4 and it works great in multiple manual transmissions. I no longer use Redline.
 
Look on either summit racing or jegs website for numerous Trans specific GL4 lubes. Like the guys said 10/30 syn is Ok also and worked great in my AX5 in my 91. The 80/90 made it literally impossible to shift when its real cold like in the single digits. Also if your jeep has a body lift verify its not the rubber boot disallowing it to go fully into gear/into the gate. Dont let the knuckleheads at the ap store convince you MT-1 is fine for your trans. Its for NON syncro buses and trucks for criminy sakes.
 
cobrasneat said:
My 91 Wrangler manual 6cyl (new to me) is kicking out of reverse gear. Before taking it apart, i want to change the fluid and see how much metal there is and what condition it's in (again, new to me). My first YJ and the first time I had a GL-5 75w-90 fluid recommended with "Safe for Yellow Metals" (i.e., usual GL-4 for toyota parts). My beach town has nothing in stock that is GL-5 but also states specifically its safe for yellow.

1. Any recommendations online on where to buy? if not GL-5, will GL-4 suffice?
2. Gear kick-out - if fluid change doesn't work, other ideas? the clutch does not seem to be sticking or not pulling all the way out.

Thank you.
Click to expand...
yes the manual is wrong, GL4 is it
but stores in town (brick) do not sell it now due to 99.99% of customer never change gear lube and drive an automatic box.
so stocking it is sill to them . for M/T
the Pennzoil yellow bottle marked Syncromess is GL4.
the bottles of all GL if marked API GL4 are in fact correctly
I run walmart Tractor oil GL4 in mine, and works great. before this for ever mostly I run the Pennzoil, and before that all stores had GL4 but not now.
GL5 is Hypoid axle lube. only. for extreme pressure gear sets. not for syncrho mesh rings that want real GL4 and are tuned for GL4
the box is designed for the rings to run normal GF4 lub back 37 years ago. not Synthetics.
and running syn GL4 can in fact make the rings slip and now all gear dogs grind or balk ! so run DINO only lube. ok?
my sons JK has no brass syncro rings (i think carbon rings ) for SYN LUBE ONLY Jeep spec., so is not the same at all as any YJ>

so your post as vast others post on line boils down to :
who sells GL4.?
google is your friend
or go to NAPA and demand special order GL4.
warning many store clerks have no idea at all what GL4 is nor what a manual transmission might be, (at all) ask the guy with gray side burns, this.
in 1/2 a day most stores can get it to you , on to counter, no $15 shipping from 3000 miles away.

yes some brands of lube are listed GL4/5, I have one bottle here from 15 years ago. (
NAPA Gear oil by Ashland of KY, made.
API
GL4, GL4, GL3 on the rear.
GL3 is obsolete now and GL4 is its replacement.
not made now. this brand version.

demand GL4 in the store. even read the rear labels in the store or online at the store, read the rear labels.
look for API GL4 marks, BINGO
 
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that is correct MT-1 is for Crash boxes,
I drove 1959 12ton dump truck in 1965/66 and it had 5speed and 3 speed "Brownie" behind it and was a crash box .that right 15 total speed. and used going up hill loaded, every time. or seen in school bus back then.
this word means , NO SYNCROmesh at all, zero . and we double clutched it. to shift, (practice it took to master it)
GL4 is best
but yes some GL5 have no yellow metal chems. to wreck them.
the old chems bad were sulfur and phosphorous. and not good to use at all in 5speed. here
and the percentage of sulfur does matter, if too much. it can eat the rings, and may only happen if water gets to the box or very humid tropics.(like)

there is no fast blanket answer, but 1, rear says API GL4. IMO. or the bottle clearly lists Synchromess in the lable.
GL4 is never used in Hypoid axles. The forces there in the offset pinion are huge!, and needs EP grade GL5/
 
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