I was wondering: can I use mobil 1 Synthetic 75w 90 fluid that is made for GL-4 and GL-5 applications on my 94 manual v6 pickup in the front and rear diffs, transfer case, and tranny? I got quite a deal on it and was hoping it wont hurt the tranny at all since it says both GL-4 and GL-5. Any thoughts?
Thanks guys.

 

I know it sounds stupid, cause I don't know all of the transmission but,

I had read somewhere that the transmission needs a gear oil for GL-5. Something about the contents of GL-4 type gear oil would screw up the brass parts inside of the tranny? Its been a while since i read that and I dont remember where I found it, sorry for the vagueness.

 

Im pretty sure its the other way around. The additives in gl-5 eat brass syncros in transmissions designed for gl-4. The rest of it should be fine with gl-5 however

 

so i should be getting something else for the tranny then...Any idea where I can find something that is specificly gl-4?

 

redline makes a product called mt-90 thats quite well regarded for many manual transmissions. if you do a search you'll come up with a few threads

 

Yep, book says GL-4 for the tranny, GL-4 or GL-5 for differentials and transfer case.

 

Actually, it lists GL-4 or GL-5 for the tranny and t-case:
- http://www.4crawler.com/4x4/4R_TechInfo.shtml#Fluids
GL-4 works the best in the tranny with the synchros (GL-5 is too slippery), the part-time t-case really does not care, mostly no synchros and no hypoid gears. The diffs need GL-5 oil for the hypoid (ring/pinion) gears:
- http://www.4crawler.com/4x4/index.sh...ntheticGearOil

 

4Crawler you're right I was looking at the Haynes manual, my bad. Factory manual does say GL-4 or GL-5

 

Ok so i guess that I can use the mobil 1 oil I have and I will be ok since the manual says GL-4 or GL-5, but I would be better off finding something that is specifically GL-4 for the tranny and should only use what I have as a last resort? am I reading these responses correctly. What I am trying to ask is will I hurt the transmision if I use the lube I have?

 

I dont know if it will specifically damage the transmission, but I know some people have reported syncro issues when using gl-5 oil in these transmissions. My recomendation would be mt-90, thats what im going to swap to, hopefully in a few weeks, due to good reviews across the board.

 

Not true for all 2nd gen tcases. The ones with ADD have several synchros inside the tcase to allow for shifting at speeds. I got a tcase that's missing one when I changed, so I can't change into 4wd unless I stop now. Oh, and I just changed my transmission fluid and used MT-90. Got it for $9.19 a quart.

 

In that case, GL-4 would be the best for the synchromesh operation, but if Toyota specs either type of oil then either one will work. Not like you are speed-shifting the t-case all the time. And of course some of the t-cases behind the automatics use ATF instead of gear oil.

 

What is the difference in GL-4 and GL-5 specifically. I am assuming just the weight? If not this is probably off base. If so, use the appropriate one for your area. SOME manual transmissions use ATF but down here, especially in the summer time I see people running light weight gear oil in them because it is a little heavier than ATF but the warm weather makes that mostly a non issue. If you are in a cold climate use the lighter weight if you are in the warmer climate, use the heavier weight. What it will affect mostly is shift feel, not damage to the transmission.

Usually if a transfer case is gear driven it will take gear oil. If it is chain driven it will take ATF.

 

the difference is that gl-5 has high pressure additives. the weight of an equally numbered viscosity gear oil is the same between gl-4, and gl-5

 

GL-1 - GL-5 (and -6) grades are a series of gear oils built for different applications. GL-1 - GL-3 are essentially obsolete nowadays, GL-4 and GL-5 are the common grades in use. The basic difference between the two is the GL-4 is for straight and bevel-cut gears, gears where the teeth mesh and transfer force without much sliding friction. GL-5 is for hypoid or helical cut gears, like the ring and pinion, where the gears transfer force while sliding past each other. GL-5 oil has the Extreme Pressure (EP) additives to keep the oil chains from shearing apart under the extreme pressure. These additives make it slipprier and may add chemicals that can attack "yellow" metals like brass and bronze, commonly used as bushings and synchro rings in transmissions. GL-4 oil does not usually have the EP additives since the straight cut gear teeth don't slide past each other. It is made more to cushion the gear teeth and is usually formulated with friction modifiers to make things like synchro rings grab better and spin up their respective gears faster.

Put a GL-4 oil in a diff and it'll break down quickly since it lacks the EP additives. Put GL-5 oil in a tranny (designed to use GL-4) and the synchros will spin up slower, shifting will be sluggish, more gear grinding, etc. I have run various GL-5 oils in my W56 5-speed (Mobil 1, Valvoline synthetic, etc.) and any GL-4 oil works better and any synthetic GL-4 works even better, especially when cold. MT-90 works great, I found MTL a bit too noisy in my area's relatively mild climate.

 

Gotcha

 

Sorry to bump an old thread, but I was just searching to see what diff oil others were running.

My manual on my 95 says of course Hypoid gear oil API GL-5 for both diffs, but for weight it says 75w-90 for ADD fronts, and in non ADD above 0 degrees F SAE 90 or below 0 degrees F 80w-90.

The rear is the same. Above 0 90W or below 0 80w-90.

Is this what most of you guys are running?

Btw, for the record the 3rd members I'm swapping out have 210k on them and are not making any noise at all and I've never changed the oil in either of them. I'm only changing them because I got replacements with 5.29's in them. I don't advocate that of course, but I'm really curious to see what they look like inside.

I used to offroad a lot but in the last 8 years or so not so much. I can't believe they're still ok.

 

I'd personally go with an 80w-90. It should act roughly the same as the straight 90 in warm weather, but you wont have quite the wear issues in cold weather.

 

Not a bad thread to revive..

I've been using M1 synth (GL-5) in my trans. and tc for a while now. I was told GL-5 synth was universal in GL-4 and 5 applications...atleast the two brands I've used, anyway. I first started using Amsoil, but that became inconvenient to keep up with. (I can't go to just any parts store and get it.) I have noticed a difference between the two in shifting. After reading this thread, I'm wondering if what I'm noticing is a wear issue over time (from the lube being GL-5) and not just a difference in lube. I replaced my shifting seat bushing when I did my clutch in Jan., so the occasional grinding and gear searching has stopped. But, the shifting is still kinda sticky. How can I tell by looking at the oil if I'm getting wear on the synchros? Can I?

 

GL-4 and GL-5 are not really interchangeable, it is not like GL-5 (being a bigger number) supecedes GL-4. GL-4 is built for things like manual transmissions and GL-5 is built for things like differentials. GL-5 tends to be too slippery for proper synchromesh operation in a manual tranny, so you get slower shifting and possible grinding because the synchro rings slip longer instead of grabbing as they do with GL-4:

http://www.4crawler.com/4x4/index.sh...ntheticGearOil