Transfer case filled with synthetic oil update

Cougar281

Well-known member
Sep 11, 2006
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St Louis, MO
I just would have assumed everyone has read or atleast been told that studies have shown that 5w-30 was overall far more superior than running ATF... i have ran 5w-30 for 2 years and don't see any signs of pump rub. When Mike switches TC's for me which will be pretty soon we'll see how much fluid i have lost to vaporization

Consider yourself among the lucky few; the pump rub problem has nothing to do with the fluid that's in the case. If the clip keeping the pump from contacting the magnesium case breaks, it will rub a hole in the case weather you have $2/qt Dex III dino or the most expensive synthetic 5W30 you can find.
 

RENODMAX

Dead Wrong
Mar 4, 2008
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I had ATF. It evaporated. Then I had oil. It didn't and was under much more stress. Believe what you like but I'll never put ATF in the tcase
 

Mike L.

Got Sheep?
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Aug 12, 2006
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Fullerton CA
So a suggestion by Rockland Standard Gear with no data to back it up is a "study"? Have you read the TC fluid sticky on DP?

You need to switch your avatar back I liked the old one better:D

The sticky at DP is a compilation of manufacturerers recomendations on their products driving them as they were intended. It was put together by a person who does not build or repair them.
I could do the same thing on heart transplants and sticky it on a medical website and it would look good cause I copied all the words correctly and made a good presentation. Would you let me do a transplant on you?

Simple fact is you will probably be all right with ATF IF you check the level on a regular basis. Most people don't including me. Therefore I use motor oil which has less of a chance to vaporize. I also believe it lubricates better under adverse driving conditions.
ATF was originaly filled in standard transmissions and then later in transfer cases for better mileage, not because it was a better lubricant.

We play hard with these trucks and need all the help we can get to keep them from breaking or wearing out parts prematurely. This is what the aftermarket hot rodders do and the manufacturersd learn from us; not from a guy behind a desk copying and pasting brochures and his claim to fame being a trans cooler hung upside down.
 

RENODMAX

Dead Wrong
Mar 4, 2008
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I dont understand why everyone thinks ATF is "superior". Doesnt that term depend on application? And our tcase is chain driven with a pump so to me oil seems more appropriate anyway.
 

Dozerboy

Well-known member
Jun 23, 2009
4,892
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TX of course
The sticky at DP is a compilation of manufacturerers recomendations on their products driving them as they were intended. It was put together by a person who does not build or repair them.
But he does have extensive knowledge of fluids which is the problem not the TC itself. No where in his post did he say 5-30 was a bad idea other then for warranty.
I could do the same thing on heart transplants and sticky it on a medical website and it would look good cause I copied all the words correctly and made a good presentation. Would you let me do a transplant on you?
F no Id probably end up with a sheeps heart.
Simple fact is you will probably be all right with ATF IF you check the level on a regular basis.
Thats what I said. If you know you have an oil leak you check it right. So if you do see know that your losing ATF you do the same. Sure its harder the pulling a dipstick, but still take less the a few mins. I maybe a little more keen on this since my job revolves around check oils ETC.

and his claim to fame being a trans cooler hung upside down.
Whats that about?



Again all I have said is that that claiming the 5-30 is better then ATF is BS and has not be proven. All we know is that it doesn't evaporate. FYI I have 5-30 in my TC, just to try it. I've never lost a drop of Syn ATF out of my TC. Even with several 2K mile plus nonstop trips at times running 90mph for a few hrs at a time.
 

RENODMAX

Dead Wrong
Mar 4, 2008
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Can I point out something kind of obvious? If you look at the MSDS for most 5W-30 oils their flash point is higher than that of synth ATFs, usually around +10* F. Many of the manufacturers dont have a boiling point or specific vaporization rate for these fluids but flash point is the absolute threshold, so if it takes 10 more degress to actually ignite motor oil that correlates to a big difference in the way that said chemical handles heat.
 
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coldLBZ

New member
Apr 22, 2007
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Alberta, Canada
I swapped to 5w30 in my T case last November. I put 3qts in through the speed sensor as well. After reading I figured I should check how much was left as my output seals sweat a bit off and on. When I pulled the plug I still must have had damn near 3 qts in there. So I refilled with 3 qts of fresh 5w30. So far so good.
 

05lly2500hd

(903)293-6026
Feb 16, 2008
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Texarkana, TX
What 5w-30 would you suggest that is more readily available?
Any opinions on Royal Purple? Is it even synthetic?
I use Rotella dino in engine, and used to use Mobil 1 in tranny and tcase.
 

JoshH

Daggum farm truck
Staff member
Vendor/Sponsor
Feb 14, 2007
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Texas!!!
So a suggestion by Rockland Standard Gear with no data to back it up is a "study"? Have you read the TC fluid sticky on DP?

You need to switch your avatar back I liked the old one better:D
What sticky? The one that Mike L. started about using motor oil instead of ATF? I can't find anything else about TC fluid. Maybe I'm blind. :confused:
 

coldLBZ

New member
Apr 22, 2007
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Alberta, Canada
I had this saved on my computer, I'm not sure if this is what you're looking for Josh. I use Amsoil in my T case.
 

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