Attention: TDR Forum Junkies 
In fact, the gear oil rating Gl-4 is equivalent to obsolete MIL-L2105 specification: usually satisfied with 50% GL-5 additive. Typical applications are manual transmissions & spiral bevel & hypoid gears in moderate service AND the New Venture 4500 manual transmission. The OEM insists that Castrol Syntorq LT be used for the NV4500, which is a not so typical GL-4 (since it is fully synthetic. ) I have found all GL-4’s to be usually mineral based. The reasons for this synthetic version are to enhance shifting problems/harshness at low temps and reduced operating temps minimizing the negative effects to “soft” metal components. The reason for a GL-4 rating is also that “soft” metal components are used in its construction. A typical GL-5 will contain approximately twice the amount of EP (Extreme Pressure) additive as that of a GL-4. When a typical GL-5 is used in a GL-4 application, the additional EP additives may have a negative reaction with the “yellow” metal components (brass, bronze, copper etc). This may contribute to chemical corrosion, etching or excessive wear over time. Lets look at the some actual performance criteria for GL and the MT-1 ratings.
Performance: Resistance to gear distress under high-torque, low-speed conditions
API GL-4: Test = CRC L-20
API GL-5: Test = CRC L-37
API MT-1: No requirement
It is interesting to take a closer look at some of these tests in more detail.
The L-20 test (covers GL-4): The test parameters for L-20 are as follows: The test axle is operated at 62 axle rpm & 600 in-lbs. of torque with no cooling water until the lubricant temp reaches 140degF. The axle is then operated for 30 hrs at 62 axle rpm & 32,311 in-lbs. of torque with the lubricant temp being cycled between 200degF & 250degF. The pass/fail criteria requires that there be no “significant” distress.
The L-37 test (covers GL-5): The test axle is operated for 100 minutes at 440 axle rpm, 295degF lubricant temp, & 9,460 in-lbs. of torque. The axle is then operated for 24 hrs at 80 axle rpm, 275degF lubricant temp, & 41,800 in-lbs. of torque. Pass/fail criteria are the same.
The L-37 test simulates a more severe service and would be more difficult to pass. Therefore, we can safely say that a typical GL-5 can handle high speed, low torque & high torque, low speed conditions significantly better than a typical GL-4.
Performance: Thermal & oxidation stability/component cleanliness
API GL-4= No requirement
#ad
API GL-5= L-60-1
API MT-1= L-60-1*
Needed for L60: a gear case assembly. 2 spur gears, 2 copper strips, a bearing, a temp control system, an alternator, a motor, & a regulated air supply serve as major components of the test fixture.
The L60 test parameters are as follows: the spur gears are rotated under load at 1,759 rpm input for 50 hrs. The lubricant temp is maintained at 325degF. Airflow through the lubricant is controlled at 1. 1 liters/hr for the test’s duration. The physical & chemical properties of the oil & deposits on the gears are evaluated at the end of the test as well as the used oil. The pass/fail criteria material percentages are noted in the actual Performance Criteria parameters, which I was unable to paste here satisfactorily. But the point is that the GL-4 has NO REQUIREMENT! The GL-5 must pass L60 & the MT-1 must pass much tighter limits of L60.
Performance:Copper corrosion conforming to ASTM D130
GL-4: 3B max after 1 h at 121. 1°C
GL-5: 3 max after 3 h at 121. 1°C
MT-1: 2A max after 3 h at 121. 1°C
Place a copper strip in the required bottle & cover two-thirds with test fluid. Heat to 250degF for 3 hrs (another source indicates 302degF). The pass/fail criteria require that there be no blackening with flaking. I have been unable to ascertain what the measurement “2A” (covering the MT-1) corresponds to, but I feel safe to assume it is LESS than the “3b” (covering the GL-4).
(Performance categories required for a GL rating but not shown due to space limitations are 1) Scoring resistance 2) Resistance to gear distress 3) Corrosion resistance in presence of water 4) Anti-wear 5) High temp lubricant stability 6) Oil seal compatibility 7) Compatibility w/ existing gear lubes 8) Solubility. Note: In all these categories the GL-5/MT-1 is equal to or better than what the GL-4 can achieve or endure. )
So, why would I use the OEM “recommended” lubricant for my NV4500? If it were before the year 1995 (MT-1 was first established in 1995) I really wouldn’t have a choice because there may not have been any better solutions. I didn’t have a PC back then & it certainly would have more difficult researching better alternatives on the www.Lets remember API MT-1 is not designated as a replacement for API GL-4. Category GL-4, which contains some obsolete test procedures, may be deleted in the future & replaced with a category that includes syncromesh performance. This category would also address the needs of light duty axles & commercial-synchromesh transmissions. BUT, considering the statistical and empirical data presented by TDR members, it appears a synthetic gear oil rated with GL-5 AND MT-1 is not just an alternative but a superior choice to what the OEM originally validated for the NV4500. It would appear the “yellow” metals issue is addressed with the MT-1 rating & the GL-5 rating can take "severe" duty service whereas the GL-4 is only rated for "moderate" duty service. Certainly, this helps explain why some TDR members such as “tdrmbramr” have had such good success with an (off the shelf-available at any auto parts store) synthetic GL-5/MT-1 rated gear oil in their NV4500. (He claims 700,000 miles recorded with all original components!). There are other TDR success stories with members using synthetic gear oil with the GL-5/MT-1 rating from a well-known private label. There are even mineral based GL-5 oils not MT-1 rated but with advertised additives specifically for this “yellow” metal problem used with good historical success. Indeed, there are good alternatives to the OEM recommended lube.
Gear oil technology is advancing and its JMO that currently a GL-5 rating combined with the relatively new MT-1 rating is THE choice for our NV4500, at least until the new rating currently being developed comes out definitively replacing the GL-4 rating. The proposed PG-2 category continues to be delayed because of problems with gear surface fatigue testing and there is no time line for completion.
The bottom line is the NV4500 is a very expensive component. I want mine to last much longer (no, I need it to last a lot longer) than the planned 100,000 mile life expectancy. A GL-4 rating does indeed seem to be obsolete for the NV4500 needs. Certainly, research & empirical data suggests that a good synthetic GL-5/MT-1 rated gear oil will not only do the job, but do a better job than the single OEM recommendation. Therefore, I will seek out a qualified synthetic GL-5/MT-1 gear lube and I might even change it periodically! If I could get only half of the 700,000 miles fellow TDR member “tdrbramr” has gotten out of his NV4500 using such a fluid, I’d be ecstatic.
WOW, that’s incredible!
#ad
#ad
#ad
Research acknowledgements: Southwest Research Institute, Inc. (SwRi) , Lubrizol Reference Library, Society of Tribologists and Lubrication Engineers(STLE), Don Johnson (VP of Product Engineering @ Pennzoil Products Co SAE & STLE member), American Petroleum Institute and the World Wide Web.
Addendum: Why would the OEM stick with just one recommendation and to one with such limited and costly availability? I don’t believe it to be such a big mystery. I made a couple of inquiries to New Venture Gear via E-mail and even submitted a more detailed version of what I wrote above. NVG responded that “the NV4500 was first developed with mineral based oil which resulted in unacceptably high operating temperatures. Castrol Syntorq was developed specifically for this application and that’s what the NV4500 was validated with. NVG has not validated / approved any other oil for use in this transmission so we can not endorse the use of any oil other than Castrol Syntorq GL-4 at this time. ”
Its seems that NVG had problems with the mineral based GL-4, requested a synthetic version to get it to work acceptably and did not research any further. To solve any legality that could arise, make it a lifetime fill. Most will make to the end of a 100K warranty, good enough. End of problem, no more expense. Lets look at it another way. They do have a full plate. They can not make enough transmissions the way it is. Look at how long it took them to come up with a good fix to their 5th gear problem,(how many years?). Look at all the reported problems with the new 6sp & how long it takes just to order one. If NVG was really paying attention do you think they would have spent all the resources to develop the new 6sp with only 550 ft-lbs of torque? TDR BOMBers have been exceeding that since day one! NVG has their hands full & have better things to do that will effect the corporate bottom line than “unnecessary” research for those hard core folks, like the BOMBers in the TDR. That’s why I find the TDR so incredibly valuable. Through the TDR one can find great people & great aftermarket manufacturers that actually care & come up with great solutions to get that Cummins power to the ground.
Its JMO!#ad
Mike
[This message has been edited by mikepvg (edited 01-22-2001). ]
Performance: Resistance to gear distress under high-torque, low-speed conditions
API GL-4: Test = CRC L-20
API GL-5: Test = CRC L-37
API MT-1: No requirement
It is interesting to take a closer look at some of these tests in more detail.
The L-20 test (covers GL-4): The test parameters for L-20 are as follows: The test axle is operated at 62 axle rpm & 600 in-lbs. of torque with no cooling water until the lubricant temp reaches 140degF. The axle is then operated for 30 hrs at 62 axle rpm & 32,311 in-lbs. of torque with the lubricant temp being cycled between 200degF & 250degF. The pass/fail criteria requires that there be no “significant” distress.
The L-37 test (covers GL-5): The test axle is operated for 100 minutes at 440 axle rpm, 295degF lubricant temp, & 9,460 in-lbs. of torque. The axle is then operated for 24 hrs at 80 axle rpm, 275degF lubricant temp, & 41,800 in-lbs. of torque. Pass/fail criteria are the same.
The L-37 test simulates a more severe service and would be more difficult to pass. Therefore, we can safely say that a typical GL-5 can handle high speed, low torque & high torque, low speed conditions significantly better than a typical GL-4.
Performance: Thermal & oxidation stability/component cleanliness
API GL-4= No requirement
#adAPI GL-5= L-60-1
API MT-1= L-60-1*
Needed for L60: a gear case assembly. 2 spur gears, 2 copper strips, a bearing, a temp control system, an alternator, a motor, & a regulated air supply serve as major components of the test fixture.
The L60 test parameters are as follows: the spur gears are rotated under load at 1,759 rpm input for 50 hrs. The lubricant temp is maintained at 325degF. Airflow through the lubricant is controlled at 1. 1 liters/hr for the test’s duration. The physical & chemical properties of the oil & deposits on the gears are evaluated at the end of the test as well as the used oil. The pass/fail criteria material percentages are noted in the actual Performance Criteria parameters, which I was unable to paste here satisfactorily. But the point is that the GL-4 has NO REQUIREMENT! The GL-5 must pass L60 & the MT-1 must pass much tighter limits of L60.
Performance:Copper corrosion conforming to ASTM D130
GL-4: 3B max after 1 h at 121. 1°C
GL-5: 3 max after 3 h at 121. 1°C
MT-1: 2A max after 3 h at 121. 1°C
Place a copper strip in the required bottle & cover two-thirds with test fluid. Heat to 250degF for 3 hrs (another source indicates 302degF). The pass/fail criteria require that there be no blackening with flaking. I have been unable to ascertain what the measurement “2A” (covering the MT-1) corresponds to, but I feel safe to assume it is LESS than the “3b” (covering the GL-4).
(Performance categories required for a GL rating but not shown due to space limitations are 1) Scoring resistance 2) Resistance to gear distress 3) Corrosion resistance in presence of water 4) Anti-wear 5) High temp lubricant stability 6) Oil seal compatibility 7) Compatibility w/ existing gear lubes 8) Solubility. Note: In all these categories the GL-5/MT-1 is equal to or better than what the GL-4 can achieve or endure. )
So, why would I use the OEM “recommended” lubricant for my NV4500? If it were before the year 1995 (MT-1 was first established in 1995) I really wouldn’t have a choice because there may not have been any better solutions. I didn’t have a PC back then & it certainly would have more difficult researching better alternatives on the www.Lets remember API MT-1 is not designated as a replacement for API GL-4. Category GL-4, which contains some obsolete test procedures, may be deleted in the future & replaced with a category that includes syncromesh performance. This category would also address the needs of light duty axles & commercial-synchromesh transmissions. BUT, considering the statistical and empirical data presented by TDR members, it appears a synthetic gear oil rated with GL-5 AND MT-1 is not just an alternative but a superior choice to what the OEM originally validated for the NV4500. It would appear the “yellow” metals issue is addressed with the MT-1 rating & the GL-5 rating can take "severe" duty service whereas the GL-4 is only rated for "moderate" duty service. Certainly, this helps explain why some TDR members such as “tdrmbramr” have had such good success with an (off the shelf-available at any auto parts store) synthetic GL-5/MT-1 rated gear oil in their NV4500. (He claims 700,000 miles recorded with all original components!). There are other TDR success stories with members using synthetic gear oil with the GL-5/MT-1 rating from a well-known private label. There are even mineral based GL-5 oils not MT-1 rated but with advertised additives specifically for this “yellow” metal problem used with good historical success. Indeed, there are good alternatives to the OEM recommended lube.
Gear oil technology is advancing and its JMO that currently a GL-5 rating combined with the relatively new MT-1 rating is THE choice for our NV4500, at least until the new rating currently being developed comes out definitively replacing the GL-4 rating. The proposed PG-2 category continues to be delayed because of problems with gear surface fatigue testing and there is no time line for completion.
The bottom line is the NV4500 is a very expensive component. I want mine to last much longer (no, I need it to last a lot longer) than the planned 100,000 mile life expectancy. A GL-4 rating does indeed seem to be obsolete for the NV4500 needs. Certainly, research & empirical data suggests that a good synthetic GL-5/MT-1 rated gear oil will not only do the job, but do a better job than the single OEM recommendation. Therefore, I will seek out a qualified synthetic GL-5/MT-1 gear lube and I might even change it periodically! If I could get only half of the 700,000 miles fellow TDR member “tdrbramr” has gotten out of his NV4500 using such a fluid, I’d be ecstatic.
WOW, that’s incredible!
#ad#ad#adResearch acknowledgements: Southwest Research Institute, Inc. (SwRi) , Lubrizol Reference Library, Society of Tribologists and Lubrication Engineers(STLE), Don Johnson (VP of Product Engineering @ Pennzoil Products Co SAE & STLE member), American Petroleum Institute and the World Wide Web.
Addendum: Why would the OEM stick with just one recommendation and to one with such limited and costly availability? I don’t believe it to be such a big mystery. I made a couple of inquiries to New Venture Gear via E-mail and even submitted a more detailed version of what I wrote above. NVG responded that “the NV4500 was first developed with mineral based oil which resulted in unacceptably high operating temperatures. Castrol Syntorq was developed specifically for this application and that’s what the NV4500 was validated with. NVG has not validated / approved any other oil for use in this transmission so we can not endorse the use of any oil other than Castrol Syntorq GL-4 at this time. ”
Its seems that NVG had problems with the mineral based GL-4, requested a synthetic version to get it to work acceptably and did not research any further. To solve any legality that could arise, make it a lifetime fill. Most will make to the end of a 100K warranty, good enough. End of problem, no more expense. Lets look at it another way. They do have a full plate. They can not make enough transmissions the way it is. Look at how long it took them to come up with a good fix to their 5th gear problem,(how many years?). Look at all the reported problems with the new 6sp & how long it takes just to order one. If NVG was really paying attention do you think they would have spent all the resources to develop the new 6sp with only 550 ft-lbs of torque? TDR BOMBers have been exceeding that since day one! NVG has their hands full & have better things to do that will effect the corporate bottom line than “unnecessary” research for those hard core folks, like the BOMBers in the TDR. That’s why I find the TDR so incredibly valuable. Through the TDR one can find great people & great aftermarket manufacturers that actually care & come up with great solutions to get that Cummins power to the ground.
Its JMO!
#adMike
[This message has been edited by mikepvg (edited 01-22-2001). ]
