thook

I found this on oildrop...
quote:
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Molakule,
I am still confused. I read your old article about GL 1,2,3,4,5, and I still don't get it.
My manual for my 95 Mitsu truck says GL5 for Differentials and GL4 for the transfer case. I put Sta-Lube GL5 in both. (before I found this site) There is a synchronizer for the transfer case because I can shift in and out of 4WD while driving. Are the brass parts in the transfer case going to get ruined? Or will this "newer" GL5 be OK?
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I cannot vouch for any lube except ours. In the past, manufactures speced GL4 because of the lower levels of the Sulfur-Phosphorous (S-P) additive package. The lower levels guaranteed less interaction (such as staining and corrosive pitting) with copper alloys such as brass and bronze.

However, and since about 2000, most additive packages now contain "inactive" sulfur which is mediated by metal deactivators and which do not allow the sulfur to interact with the copper-alloy metals, but still allows the S-P additive to protect the gear teeth and bearings.

The problem with most OTS GL5 lubes in MT's is their viscoity and friction modifiers. While the OTS GL5 gear lubes are great for differentials, they do not possess the correct viscosity or friction modification for smooth cold weather shifting.

Some newer MT lubes, such as our MTL-P and MTL-R, are dual-rated GL4/5 for maximum protection in manual transmissions and transaxles, and contain special friction modifiers for synchros."

After reading this and looking over the specs on RL lubes I answered all but one question. How can the two oils, the tranny and t/c, mix?

BeachRNR

Thats what I am wondering.

4Crawler

iTrader: (3)

Tranny and t-case are bolted together, there is a seal on the shaft connecting them. Seal leaks and oils can mix. Unlikely to leak enough to cause any major mixing, but some folks worry about that.

GL5 oil won't "eat" the inside of the Toyota tranny or t-case up, thus the reason it is speced for GL4 *or* GL5 oil. The sulphur additives in the GL5 oil, when it was first introduced, likely did attack the older design transmissions. I suspect that auto makers figured out how to develop new "yellow metal" alloys that were tolerant of the GL5 additives for use in bushings, synchronizer rings, etc. shortly after GL5 oils became common.

So if you are using a GL5 oil in your tranny, and it is working for you, you are probably fine to leae it be. I've used GL5 oils (conventional and synthetic) in my W56 5-speed and I have also used GL4 oils and I find that the GL4 oil *works* better than the GL5 oil. Shifting is faster and crisper. I also find that a synthetic oil makes the transmission and t-case run cooler than a conventional oil. So I run a synthetic GL4 oil in the tranny and a synthetic GL5 oil in the t-case. Why GL5 in the t-case and not GL4? I was out of GL4 oil (MT90) after last filling the tranny and I had enough Redline 75W90 gear oil to fill it, so that is what I used. The RF1A t-case is not syncromesh and MArlin also recommends GL5 oil in the dual t-cases and/or w/ crawler gears.

Flamedx4

I'm always amazed at these types of threads.
First off, be very carefull when you decide to run *anything* other than whatever the mfr recommends. Lotsa unintended stuff can happen.
Second, why do you guys want to spend 2 or 3 or 10 times more for "synthetic" or whathaveyou? There are millions of long life vehicles out there who never saw anything but petro, often CHEAP petrol based products. NO ONE has EVER produced any evidence that your engine or transmission will benefit from synthetics, but there are many many known cases where premature failure occurred due to the lube properties of very expensive synthetic not doing the job properly, especially if the engine or trans wasnt' started off NEW with synthetic.

I am not saying that synthetic use is wrong, or even necessarily bad, it's just that it amazes me that so many people will blindly pay all that money for it when it's never been proven to prolong engine life.
You will get far more benefit out of doing the correct interval oil changes (or even more frequent than recommended) with any name brand oil. THAT has been proven time and time again.

One last thing, I work with engine and transmission manufacturers on a daily basis, and have negotiated warranties and the like for their products when my company uses them. I can tell you for certain that if they say 10w-40 oil or Dextron that's what the MEAN, and when we talk to them about alternative oils they flatly don't want it condoned. It's designed for the lubricants they state, and nothing else. And, if your engine or transmission fails and has synthetic oils in it (and they don't tell you in their manuals that it's okay) then you will be on your own warranty-wise... That's all I need to know.

4Crawler

iTrader: (3)

I can feel the difference in operating temperature on my '85 with synthetic. Probably a good 20F cooler compared to conventional oil, so that is one reason I run it. With dual t-cases, I get a *lot* of heat off of them (into the cab), especially at high speed and in high ambient temps, so that temperature reduction is significant. I also run synthetic oil in the transmission because it shifts better and the other reason I run synthetics is for their longer service life. I can get more than twice the service interval on synthetic gear oil than with conventional and I also have better things to do with my time than draining and refilling the tranny, 2 t-cases and 2 differentials with about 3 gallons of smelly 90W every year or so. And one side benefit of at least Redline synthetic is that they have a much lower odor than conventional oils. With dual t-cases, I tend to get whiffs of gear oil into the cab if the wind and driving directions are just right, so a low odor oil is another plus.

I do run conventional engine oil and change it frequently.