So it took a while and almost bought the wrong fluid. But here it is, Valvoline Heavy Duty sae50 Full Synthetic. It has to be part# val 706035m The first NAPA parts person tried to sell me what they thought was full syn. but its not. That part number was 329, wrong fluid. The guy came to me and said your running a Dodge, right? And right then I said this is the guy I need. Had my nv5600 rebuilt and the builder said good to go, he recommends it over Amsoil 5-30. Its to thin down here, 50 weight is needed.

Curious to see how it works out, as the NV5600’s synchros are generally not fond of GL-4 fluids. 

Comes recommended by SuperStick transmission. He races what he builds, fastest manual builder I know of. My nv5600 was just built with Super Synchros, what those are I dont know but he is one if not the best rebuilders. The pto covers have a bluish tint right in the center where the gear splashes oil that tells me friction is high. It needs a thicker oil, I dont see how a 5-30 in south Tx pulling 17-19k trailers is ever going to do the job. At this point I dont see anyone building a oil to fit the needs of these transmissions. What choice do we have? I know of several people with over 80k using this oil. Im jumping in with both feet and I'll let you know what happens.

The 5-30 rating of synchromesh isn't on the gear lube index, it's on the crankcase index. If it were rated like a gear oil it would be closer to a 70-85w and the SAE50 is like a 90wt, so there isn't nearly as much difference as you think, nor it is all that thin. 

 

It may or may not be thick enough for the NV5600, but I do know the NV5600 was never rated for that much weight. The highest GCWR I've seen associated with a NV5600 is only 23,000K lbs. That alone could be why the 5-30 hasn't really been an issue. Then again I never really paid attention to the factory GCWR with my NV5600 and never had any issues upwards of 26K GCW with ~1000 lb/ft at the flywheel. 

 

Kinda funny that superstick told you to run the SAE50, but they only sell the Amsoil Syncromesh on their website, but their website does leave a lot to be desired. I do read about them every now and then, but not very often, so I'm excited to see how this works out for you. 

I dont follow what your saying, Amsoil 5-30 synchromesh isnt on the gear lube index its on crankcase? When I say 17-19K thats combo weight. I have tip the scale at 27K once with this truck. Summer time temp somewhere around 100, with temp gun was approx 175 with Amsoil 5-30. Ive got a report coming back as of today. Ive been hauling same weight travel same rd same speed on return. Temp outside has been 75 both days. One more load to haul tomorrow with another oil. Granite this is no scientific test its all on temp.

1 hour ago, jlwelding said:

I dont follow what your saying, Amsoil 5-30 synchromesh isnt on the gear lube index its on crankcase? When I say 17-19K thats combo weight. I have tip the scale at 27K once with this truck. Summer time temp somewhere around 100, with temp gun was approx 175 with Amsoil 5-30. Ive got a report coming back as of today. Ive been hauling same weight travel same rd same speed on return. Temp outside has been 75 both days. One more load to haul tomorrow with another oil. Granite this is no scientific test it’s all on temp.

I’m pointing out that 5-30 Syncromesh isn’t as thin as it sounds. Despite being a transmission fluid it’s rated on the same scale as engine oil (crank case) not gear lube, same as the fluid you’re running now. There just isn’t a lot of difference between the 30wt and 50wt scale, similar to going from a 85wt gear lube to a 90wt gear lube, overall pretty negligible. The biggest difference you’ll likely see is the cold fluid performance will suffer with the 50 as it’s much thicker cold. I know plenty of folks who jumped on the 50wt wagon with their G56’s and dumped it fast due to cold weather issues. 

Yes, there is a big difference is saying 17-19K GCW vs 17-19K trailers… 

 

175° in 100° heat is perfectly acceptable, and sounds about where it should be. 
 

Temp gun can be deceptive too. I recall the great debate on overfilling the NV5600 as fluid temp rose, but what did bearing temp do? 

 

On 12/6/2022 at 6:39 PM, AH64ID said:

I know plenty of folks who jumped on the 50wt wagon with their G56’s and dumped it fast due to cold weather issues. 

 

Just to point out that I've got a customer (2006 G56) that opted for the 50 SAE trans fluid over the ATF+4. No issues to date and still shifting good. I've still got 50 SAE in Beast (NV4500) and shortly going to swap out the ATF+4 in Thor (G56) for 50 SAE as well.