G56 fluid ?

[jhenderson]

EMAC2, Fred Easley, was the only source for Mobil-Trans SHC-MB that I am aware of, and then Mobil made a decision to get out of this market. Some suspect the Delvac 50 was and is the direct replacement; others would take exception to this statement. In the meantime, Fred who was an active contributor on this forum, developed the "death wobble" on his truck and the last time I talked with him several years ago had gotten rid of his ride. The test I cited by CarboniteCummins didn't include Amsoil unfortunately. It does show, rightly or wrongly, the correlation between Mobil-Trans SHC-MB and Delvac 50. When the day is done, most of us would agree that ATF is not the ideal fluid, especially when pulling heavy which most of us do. We are therefore left to our own devices and there are numerous alternatives out there. Chrysler, who is noted for short-cuts, especially on third-generation and before trucks, has dealt all of us a 'bad hand' that should rank up there with poor filtration and premature injector failures due to their ignoring Bosch and Cummins on the recommended primary filter specs. As I have said, I use the Delvac 50 and I am well satisfied. There are other alternatives and I certainly wouldn't say my decision is any better than anyone else's. I do go one step further and monitor transmission and differential temperatures and drive accordingly.

- Ed

All that's needed is a trip to the Mobil website. Look up the tech spec sheets on both fluids. They're virtually identicle.

 

[Newsa]

ATF is roughly a 75wt gear oil hot and cold.

Towing mostly light (4500 miles) & heavy a little (500 miles). My original ATF and magnetic drain plug looked better at 3.87 years (30850 miles) than my rear differential did at 1.85 years (16,100 miles) and my front differential did at 3.82 years (30,400 miles).

I will come back to this thread in a little over 3 years and upgrade to Amsoil MTG. That's when my max care expires. I think I will reach 7 years before I reach 70,000 miles. Or if I drive from Florida to Oregon a few times, maybe not?

 

[Newsa]

I have been advised to not mix engine oils (weights and/or brands).

But I find it curious that redline recommends mixing their MT-90 (Which is a 75w 90 manual transmission lube) with their 75w140 ns (differential oil ) if you have a noisey or older manual transmission.

I see this recommendation on redlines website to increase viscosity. And there are some who swear by this combination.

Why would it be different for engine oils?

 

[RVTRKN]

Why such a heavy viscosity? Synthetic 50wt manual trans oil I use, works great. The plus is I use it in my transfer case as well.

 

[AH64ID]

Why such a heavy viscosity? Synthetic 50wt manual trans oil I use, works great. The plus is I use it in my transfer case as well.

It's actually about the same thickness. 75w-140 is thinner when cold and thicker when warm than SAE50.

ATF also isn't nearly as thin as most people think. It's thinner for sure, but nothing crazy. At 40° C it's about the same as thick as a 75w gear lube and when warmed up it's about as thick as a 80wt gear lube, so it doesn't change much.

 

[Newsa]

It's actually about the same thickness. 75w-140 is thinner when cold and thicker when warm than SAE50..

My research (just layperson internet research) confirmed this.

I still have ATF in mine. I have 2 1/2 years on my max care.

 

[Newsa]

ATF is roughly a 75wt gear oil hot and cold.

ATF is adequate. I was under the impression it doesn't thin as much as 75wt when hot?

 

[Killer223]

I didn’t think the 75-140 was safe for these cause the sincros.?. Something about GL5 not safe for yellow metals.

 

[AH64ID]

I didn’t think the 75-140 was safe for these cause the sincros.?. Something about GL5 not safe for yellow metals.

Correct, GL-4 is what MB recommends.

 

[Newsa]

I didn’t think the 75-140 was safe for these cause the sincros.?. Something about GL5 not safe for yellow metals.

https://www.redlineoil.com/75w140-ns-gl-5-gear-oil

Yes. True.

But take a look here

 

[Newsa]

Redline ester base oils have such strong film strength, they don't use as much high pressure additive as others. And when diluted 50/50, they say it is safe.

 

[AH64ID]

I don't understand the need for mixing when there are quality synthetic GL-4 75w-90 lubes, just like MB recommends.

 

[Newsa]

I don't understand the need for mixing when there are quality synthetic GL-4 75w-90 lubes, just like MB recommends.

Yeah. I see your point. I used to think thicker was always better. And It's hard to change 40 years o f thinking. With these new oils that can withstand high temps, sometimes thinner can help it cool better and still lube adequately. I don't think I would go with straight 50 though.

As for engine oil, I don't think mixing weights is necessarily bad. But probably doesn't achieve what the owner is trying to achieve
And as for engine oil, I prefer 15w 40 to 5w 40. Still like the heavier weight there even in sub zero temps. I noticed there are some synthetic 15w 40 weights that flow better than 5w 40 weights when below zero. They are the more expensive synthetics though.

 

[TRAMPLINEMAN]

ATF is adequate.

I have to disagree. When it’s -30 to -40 and you can’t shift gears using both hands, that’s not even close to adequate.

 

[Regcabguy]

Mine's a bit stiff even in San Diego in winter with the MTG but it is slicker than the Delvac 50 I used prior.
I drive in 2nd for a couple blocks in my neighborhood and everything's kosher for the rest of the day.

 

[TRAMPLINEMAN]

When I had the MTG and ATF in the transmission I had to be sure to back the truck into the driveway and park it in 2nd. If not, my wife could not get it into gear in the morning to go to work. Many days she drove three miles to work in 2nd cause it wouldn’t go into 3rd. This problem did not exist with the original fluid, it shifted great in any weather. We’ve been running Royal Purple Synchromax this winter and have had zero shifting issues.

 

[Regcabguy]

A lot of us are running the thicker fluid to quiet down the trans gear rollover.
I believe Standard Transmission recommends a 5-30 synthetic synchromesh for the G-56.

 

[RVTRKN]

Yeah. I see your point. I used to think thicker was always better. And It's hard to change 40 years o f thinking. With these new oils that can withstand high temps, sometimes thinner can help it cool better and still lube adequately.

That is correct, my trans runs hotter with the heavier 50wt oil than 50% Royal purple/50wt. The thicker the oil the harder for it to transfer the heat. That's one of many reasons for my cooler setup. For the G56's still running the DMF, you could practically pee into the trans, and its going to sound OK. The heavier oils should be used when the "pressure plate flywheel/G56" has been converted to the SMF. If your going to go heavier than OEM, add a temp sensor and know the difference in how hot it gets, you might just go back to ATF with a DMF, because it'll run cooler and still be quiet.

 

[Regcabguy]

That is correct, my trans runs hotter with the heavier 50wt oil than 50% Royal purple/50wt. The thicker the oil the harder for it to transfer the heat. That's one of many reasons for my cooler setup. For the G56's still running the DMF, you could practically pee into the trans, and its going to sound OK. The heavier oils should be used when the "pressure plate flywheel/G56" has been converted to the SMF. If your going to go heavier than OEM, add a temp sensor and know the difference in how hot it gets, you might just go back to ATF with a DMF, because it'll run cooler and still be quiet.

Yeah,I ran a 60hp Smarty tune,34's and an 1800# camper for 37K on mine. It would likely still be in there if I didn't get talked into getting the smf conversion. The installer said it was like new. I had a seeping rear main which necessitating removing the trans. I miss that near silent trans. I asked LuK to consider a 60hp+ dmf when I had mine. No dice.

 

[Newsa]

Mine is quiet. So I see no need to put anything heavier (more viscous) than 75w 90.

I just thought it curious that a synthetic oil manufacturer was recommending mixing weights. Especially since GL5 fluids are known to be harsh on synchros.

I will stay with the DMF. And will have it checked (possibly replaced) when my clutch goes. I haven't been towing heavy enough lately to rrequire a more stout flywheel/clutch set up.

I think ATF is adequate. But I doubt It's lubrication qualities can match a real manual transmission lube. ATF has lube qualities, but was designed to transfer loads (fluid pressure) in addition to lubricaring. After my max care expires (only have about 7 months left on the Power train warranty, but have 2 1/2 years left on the max care), I plan to change to redline mt-90. It is a top quality 75w 90 transmission lube.

I often use amsoil products. But I think redline is much better. And if I'm going to leave it in there a couple of years (just top off when needed), I want a good lube in there.