90wt or 85w-140???

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Rifleman
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90wt or 85w-140???

Post by Rifleman » Thu May 15, 2014 10:19 am

I think I have read about every thread here on lubes and I must say I don't feel super confident about any direction with the possible exception of simply using a GL4 compliant straight 90 weight in everything with gears.

I understand the stated possible risk to seals from using synthetics and I am fine with staying with conventional oils.

I recently acquired my truck and the owner provided two 5 gallon pails of conventional 80w-90. One is GL4 and one GL5. I am assuming from most recommendations here along with the factory specified straight 90 that the 80w-90 is actually thinner than optimal for my warmer climate?

I like the idea of realizing a gear noise reduction from using the ideal lube as long as there is ZERO detrimental effects.

My specific question is; Would Chevron Delo 85-140 ESI be a good choice in all the gear boxes and differentials with the exception of a GL4 compliant 90wt in the transmission?
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Jimm391730
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Re: 90wt or 85w-140???

Post by Jimm391730 » Thu May 15, 2014 11:39 am

I've learned more about GL4 vs GL5 and gear oils than I ever really wanted because of the Pinz.

First, lets discuss weights: Yes, the higher weight oils are thicker. The multi-weight oils (80W-90, for example, or 5W-30 for modern car engine oil) are really the low weight oils with long polymer "strings" blended in. All oils thin as they get hot, but the long strings help to increase the viscosity as the oil temp increases. The problem is that lubricating gears with this type of oil, the gears tend to grind up the long strings and gradually destroys the heavier weight advantage (engines don't tend to grind up the oil as much, so the multi weight engine oils tend to work better and allow a greater variation between the weights for the life of the oil). This is why many gear oils are only 80W90, or 75W90, etc., with only a small difference in the weights (the 85W140 being an exception). Since gearbox oils don't get contaminated by combustion byproducts (like engine oils) they last a long time before they are replaced (if ever, on some vehicles). With that in mind, the 85W140 may end up being mostly just 85 weight after a while. Of course modern oils tend to be better at reducing wear than older oils so it is possible that the thinner oils actually give better protection than thicker, older oils. It also depends on the size and type of gears -- small gears, with high power engines, have much more force per area on the teeth and require a better lube to prevent wear . Our older design Pinzgauers, with big, beefy gears, no hypoid gears (what allows most differential inputs to be lower than the centerline of the axle) are not forced to use such improved lubes as more modern vehicles. This is not to say that we don't want to use the best. But you will want to choose the proper weight oils for your climate.

Modern gear oils have sulfur and phosphorous additives that create a coating on the steel, and this coating helps to prevent steel to steel contact even if the oil film is squeezed out by extreme pressure. GL5 has about twice these additives than GL4. They don't actually "corrode" the brass/copper in gearboxes, but since they coat everything they cover the syncros. Since the transmission's syncros are designed to create friction to match shaft speeds for smooth gear changes, the coating gets stripped away. The problem is that the coating is tougher than the brass, and the adhesion to the brass is stronger than the brass; so as it is stripped away on every shift it rips a bit of brass away, too. So the brass gradually is torn away, resulting in "wear" since the size of the brass syncros changes. Since GL5 has more of the coating additive, it wears out the syncros faster. There is a great difference between "gear oil" and "transmission oil"! Just because our manual transmissions have gears does not mean gear oil is suitable. The "GL" rating comes from a test procedure that would measure if an oil gave sufficient protection from wear. Gear oil manufacturers may say "suitable for GL3, GL4, and GL5 applications" since their oil will protect for all three of the increasing severity of the wear test. But if you look closely you may note that there specs do NOT typically mention transmissions; they will say "for gearboxes" which is NOT the same thing.

When I got my first Pinz years ago I put GL5 in the transfer case without any issues at all. Why? Because the transfer case is rarely shifted; and some shifts are with zero speed so no noticeable damage is done to the syncros. I also put 85W140 in the hubs and diffs, thinking that the heavier weight would be "better". But at freezing temps I couldn't go faster than 45mph as the thick oil just dragged so badly on the moving parts. So I have gone back towards a good quality 75W90 in the hubs, diffs, and transfer case, where GL5 will work just fine (and is mostly all that you can find).

I use Redline MT90 GL4 in the transmission which is specifically formulated to be a transmission oil. It has given me (and others who have tried it) very noticeable improvements in shifting across a wide temperature range and is a good choice for our transmissions (it is not the only good choice, I'm sure there are others). As long as it doesn't leak, you won't need to change this oil for many, many years since there is no combustion contaminants to degrade the oil. Almost any gear oil will be acceptable for lubrication of the rest of our gearboxes.

So really we need two, possibly three types of oils in our trucks: engine oils (pick your poison), transmission oils (you might lump the transfer case in with it, but that's been discussed above) and all the rest: diffs and hubs. I suspect that most owners can choose their oil weights based on their use and climates but I hope I've helped to clear up some misconceptions about the GL4 and GL5 issues.

Sorry for the long winded text.
Jim M.
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Re: 90wt or 85w-140???

Post by Rifleman » Thu May 15, 2014 1:52 pm

So the synthetic Redline in the transmission has not exhibited any compatibility issues with seals?

From your experience with the 85-140 and cold temp it sounds like the 80w-90 I have on hand may be fine?
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Jimm391730
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Re: 90wt or 85w-140???

Post by Jimm391730 » Thu May 15, 2014 4:03 pm

So the synthetic Redline in the transmission has not exhibited any compatibility issues with seals?
As I recall, when the synthetics first came out they tended to NOT swell the rubber seals as much as the dino oils did; so things that did not leak with dino juice then leaked badly when changed to synthetics. But that was corrected decades ago and now the synthetics have very similar effect on seals, so IN GENERAL they are equivalent. That is not a guarantee of performance, but mostly considered an old wives tale anymore. I've not had any problems with the MT90.
it sounds like the 80w-90 I have on hand may be fine?
That's probably right for Tennessee (at least compared to 140 weight). 140 might be appropriate in the hot portions of Arizona or similar, but even then may not be necessary. Even though I occasionally spend a few days in the heat of Mojave or Death Valley I have changed away from the 140 weight oils.
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Re: 90wt or 85w-140???

Post by Rifleman » Thu May 15, 2014 9:46 pm

Thank you sir. I went ahead and flushed all the hubs and re-filled with the GL-5 80W-90 I had on hand.

I will probably go with that MT90 for the transmission too. Do you use it in the transfer case as well or just the transmission?
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Re: 90wt or 85w-140???

Post by VinceAtReal4x4s » Thu May 15, 2014 11:21 pm

Redline MT90 -transmission
Redline Heavy Shockproof -diffs and transfer
Conventional 80 or 90 or whatever you have for the hubs.
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Re: 90wt or 85w-140???

Post by John L » Tue Sep 02, 2014 9:33 am

Jim:

Thanks for taking the time to fully explain the GL4 vs 5 and the varying weight options for the oils. I was totally confused and your post cleared it up. I'm in the process of changing the oils im all of my hubs, diffs, transfer case, and transmission and wanted to understand what I needed. I just received the hex plugs from Scott and plan to complete my project this week. Just a word of thanks for taking the time to help us out! :lol:

John

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krick3tt
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Re: 90wt or 85w-140???

Post by krick3tt » Tue Sep 02, 2014 11:59 am

If you are intending to install a hex plug in the oil pan, it might be worth reconsideration...it is recessed for a reason.
I have also purchased new hex plugs for all my drain and fill locations and when it is time to change the oils I will be installing them like you are planning. New gaskets/sealing rings as well
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Re: 90wt or 85w-140???

Post by edzz » Tue Sep 02, 2014 2:16 pm

And remember remove the fill plug first.
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John L
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Re: 90wt or 85w-140???

Post by John L » Tue Sep 02, 2014 4:40 pm

krick3tt wrote:If you are intending to install a hex plug in the oil pan, it might be worth reconsideration...it is recessed for a reason.
I have also purchased new hex plugs for all my drain and fill locations and when it is time to change the oils I will be installing them like you are planning. New gaskets/sealing rings as well
You are probably correct. I don't do a lot of rock crawling in Louisiana; but I do climb over trees and such. I'll probably leave the drain plugs as original and change out the others. Thanks for the tip!

John

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John L
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Re: 90wt or 85w-140???

Post by John L » Tue Sep 02, 2014 4:42 pm

edzz wrote:And remember remove the fill plug first.

Got it! :D

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mm58
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Re: 90wt or 85w-140???

Post by mm58 » Tue Sep 02, 2014 6:55 pm

I nominate this thread (Jim's info) to be a sticky
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Re: 90wt or 85w-140???

Post by audiocontr » Tue Sep 02, 2014 8:53 pm

VinceAtReal4x4s wrote:Redline MT90 -transmission
Redline Heavy Shockproof -diffs and transfer
Conventional 80 or 90 or whatever you have for the hubs.

Heavy shock proof is over $250 for a 5 gal tub. Is it worth the 5x cost of Coastal GL5?
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Jimm391730
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Re: 90wt or 85w-140???

Post by Jimm391730 » Wed Sep 03, 2014 12:26 am

Heavy shock proof is over $250 for a 5 gal tub.
If the diff doesn't leak (and you don't get it contaminated by water pretending to be a submarine) then you only need 2 liters per diff. Why buy so much?
Jim M.
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