Getrag vs. NV4500 lubricant

[driverswanted]

My '91 manual for the Getrag indicates that a SAE 5W-30 engine oil with classification SG or SG-CD should be used. Why is this such a discrepancy when comparing the NV4500 required lubrications? I know about the non-metalic synchros in the NV4500 but would not the forces on the gears of a Getrag 360 warrant a heavy weight gear oil?

 

[1stgen4evr]

lubrication

I haven't had a fire baptism in a day or two. So I will see if I can get this thread in high gear. I have a 93 with the getrag. The only problem the getrag has ever had was caused by me and so I don't hold any ill will toward the getrag. When I had the transmission out the first time at about 125k, I felt that the lubrication was inadequate. I (and I alone) decided that it needed a heavier film strength lube. When I reinstalled the transmission, I filled it with aw 85 gear lube. I noticed that the transmission needs a minute or two to warm up before it shifted as normal with the motor oil.



But I have subsequently run the truck another 375+k miles. I have had the transmission out once when replacing the throwout brg and reshimmed at that time. It now needs the third gear syncro and will have to be out some time soon. I looked into the side cover and the gears are mirror bright and all else is well in the transmission. My truck is twd and I have no power upgrades and may not be producing even the advertised stock HP. The Cummins, the truck, 85aw and the getrag have done me a completely satisfactory job. Now you can take that for what it is worth. Two cents?



OK. I'm suited up. Bring on the flame throwers.



1stgen4evr

James

 

[GTX_Joel]

Just out of curiosity James, do you ever tow with the truck, and if so do you tow in overdrive? I don't like the automatic in my truck at all and keep thinking about swapping in a manual, like a getrag.

 

[CToney]

transmission oil

The getrag calls for a 5w30 engine oil and the NV4500 calls for a GL-2 75w90 gear oil both oils are essentially the same weight. Gear Lubes have a different number than the same weight of gear oils so they don't get confused with one another. A GL-2 doesn't have extreme pressure additives that chew up sychros. I run synthetic 0w40 diesel oil in my getrag for better low temp performance and higher temp stability. The additives in the engine oil that deal with soot and combustion acids aren't needed but it is ok on the synchros. My brother runs mopar 75w85 in his NV 4500. You could probably run a GL-2 in your getrag with no problem.



CR Toney

 

[1stgen4evr]

James do you tow in overdrive?

I answered GTX in a PM but for the forum, yes I tow in OD. I didn't for a long time but as I got more miles and was comfortable with the truck/transmission I did it more and more to the point that now I use OD loaded or empty.



Maybe I got a "good one" but my Getrag has been excellent. Maybe I don't use my truck as hard as some. I can't say. I conceed that application is everything in terms of service life. That would apply to lube as well.



1stgen4evr

James

 

[Bob Beauchaine]

The Getrag calls for 5W30 preferably synthetic do to the tight tolerances built into the German made Getrag. It is generally agreed by most Gertag drivers that a 1 qt overfill is benificial the these transmissions.



The NV4500HD requires GL4 75W90 synthetic when used behind the Cummins. GL4 75W90 is the approximate SAE weight of 20W50 engine oil.



What you use is your call. I tried 5W50 synthetic in mine before I gave up due to the noise of the Getrag.



Bob

 

[driverswanted]

Thanks 1stGen, Joel, Bob

Informative lesson on GL vs. SAE specs. I've copied these replies and inserted them into my manual.

BTW I did the rebuild on my Getrag about 30K ago and did the street Ell pipe fitting additiion to get one more quart in. Have to drop the the unit again though because either my pilot is chirping on clutch engagement or I have something wrong in the clutch itself. Anyway I'm not risking running it anymore until I find the cause of the noise. if it's a worn pilot I know that will start to destroy the transmission again. One getrag rebuild is enough for me.

 

[JLEONARD]

The additives in the engine oil that deal with soot and combustion acids aren't needed but it is ok on the synchros.

I'm glad you recognize this point... . you get credit in my little book.



I only say that because it reminds me of a friend of mine.....

He runs a certain engine oil in his boat transmission because it meets a Cat transmission spec.

He also uses the same oil in his Perkins diesel..... but for the same reason... it meets the Cat transmission spec.

Makes no sense whatsoever to me... . but he's my friend so I ignore him on that point.

Jay