RK55 front axle gear oil spec

[cdb2]

Just a note for the other RK55 owners out there who do their own scheduled maintenance.

The manual specifies GL-4 gear oil for the front axle which is hard to find locally, so I emailed them and they recommended a Harvest King GL-5 oil. I asked for clarification and got word from them that according to TYM engineering the manual is in error and it's fine to use either GL-4 or GL-5 oil in the front axle. Hope that helps anyone else looking for the right fluids for their service.

 

[TractorNH]

In my research on this I found that GL-4 is Hydraulic Fluid but GL-5 is different and has a different additive pack than GL-4.

I have a Mahindra 2655 HST which is the same drivetrain as your RK55 and the TYM T554. While the TYM Manual says to use GL-4 and calls it "Gear Oil" the Mahindra manual indicates "Mahindra universal tractor hydrauliuc fluid" is acceptable for the front axle. The TYM Manual also lists different hydraulic fluids by name so what I am using now is the Chevron 1000 THF for transmission/hydraulics and front axle. The Chevron oil is available at Napa stores.

Here is a screenshot of the TYM T554 manual for the oil types:


Here is the Mahindra 2655 manual for the oil types:


And here are the acceptable oil brands listed in the TYM manual:

 

[cdb2]

In my research on this I found that GL-4 is Hydraulic Fluid but GL-5 is different and has a different additive pack than GL-4.

Yep, I came to the same conclusion after reading what I could on it, which is why I was hesitant to use the GL-5 when the manual specified GL-4. But, since the RK tractor people checked with TYM engineering and they concluded it's safe to use GL-5 that seems to answer the question clearly at least so far as the RK55 is concerned.

 

[TractorNH]

Yep, I came to the same conclusion after reading what I could on it, which is why I was hesitant to use the GL-5 when the manual specified GL-4. But, since the RK tractor people checked with TYM engineering and they concluded it's safe to use GL-5 that seems to answer the question clearly at least so far as the RK55 is concerned.

I've learned over the years not to hang my hat on a "he said it will work" type of statement. I've seen too many people given incorrect info by dealers in several brands and without having it thoroughly documented or without being able to validate the statement through other sources it's risky to just accept what they say. I'm not saying they're wrong, just that I don't trust those types of statements. I prefer the approach of being able to actually document the logic as I've shown above which is far from easy to do at times.

 

[Ford850]

Here's a good description of both.

GL-4; Specified for hypoid gear service under severe service but without shock loading. This classification is essentially obsolete but is still specified by some manual transmission/transaxle manufacturers. Implies an EP/AW additive package that contains 30% to 50% less S-P additives than the GL-5 service classification. Some Marine Gear Lubes fall into this classification, especially the full Synthetic Marine Gear lubes and specialty blenders MT lubes that use high levels of esters.

GL-5; Specified for hypoid gear service but with shock loads and severe service operation. Usually meets Mil-L-2105D and in most cases, is the multipurpose automotive gear oil. Most 75W90 to 75W140 grades meet the GL-5 classification. This grade has a high level of Extreme-Pressure additives that could be mildly corrosive to nonferrous parts, such as brass, bronze and aluminum parts. Most of the modern GL-5 lubes contain metal deactivators that prevents attacks by the extreme-pressure additives. In addition to EP additives, these lubes contain rust inhibitors, defoamants, friction modifiers, thickeners, and Viscosity Index Improvers. ​

Gear Tribology and Lubrication - Part I - Bob Is The Oil Guy

 

[cdb2]

I've learned over the years not to hang my hat on a "he said it will work" type of statement. I've seen too many people given incorrect info by dealers in several brands and without having it thoroughly documented or without being able to validate the statement through other sources it's risky to just accept what they say. I'm not saying they're wrong, just that I don't trust those types of statements. I prefer the approach of being able to actually document the logic as I've shown above which is far from easy to do at times.

For a random dealer sure. But this is from the engineering department of the tractor manufacturer themselves, via the service department of the company who warranties them. Hard to find better info than that.