Search Results

In electric or hybrid electric transmissions, the transmission fluids can be in contact with the parts of the electric motors, for example, electrical windings in the stators in order to efficiently cool the electric motors and to insulate the electrical parts to prevent a short circuit of the electric motors. The transmission fluids must therefore have low electrical conductivities [1,2,3,4,5,6,7,8,9]. Transmission fluids contain dispersants, which can be reaction products of hydrocarbyl substituted carboxylic acids or anhydrides and amines. These dispersants can be further post-treated with boron and phosphorus compounds to improve friction and anti-wear properties. Certain dispersants, which have nitrogen content up to 10,000 ppm by weight, and boron plus phosphorus to nitrogen ((B+P)/N) weight ratios of from 0.1 to about 0.8 : 1.0, were found to be effective to provide low electrical conductivities less than 1,700 pS/m [10].

This paper reports its findings in three separate parts. First, a comparative study is made among existing commercial dual clutch automatic transmission fluids (DCTFs). Significant differences in fluid torque capacity, friction material compatibility and copper corrosion performance were found among the fluids. Second, both a new vehicle chassis dynamometer durability test and a SAE#2 durability procedure are offered, specifically designed for DCTs. A 2008 VW GTI did well in the severe 60,000 mile chassis dynamometer procedure. Third, a new DCT fluid is discussed.

An automatic transmission planetary gear fatigue test is used to screen lubricant performance of various automatic transmission fluids. The key use of this test is to assess the ability of a lubricant to extend or limit planetary gear system fatigue life. We study the fatigue behavior in this test and find the major failure modes are tooth macropitting, and macropitting-related tooth fracture of the sun and planetary gears (short and long pinion gears). Micropitting appears to be responsible for these gear failure modes. Macropitting is also seen on the shafts and needle rollers of the bearings. Gear tooth fracture appears to have originated from the surface as a secondary failure mode following macropitting. Bearing macropitting is initiated by geometric stress concentration. Bending fatigue failure on the sun and planetary gears also occurs but it is not a micropitting-initiated failure mode.

The effects of the cetane improvers* 2-ethylhexyl nitrate (EHN) and di-tertiary-butyl peroxide (DTBP) on regulated exhaust emissions from a 1993 Detroit Diesel Series 60 heavy-duty diesel engine were studied. EHN and DTBP were added to two commercially available fuels at concentrations ranging from 500 to 12,000 ppm by volume. Both additives reduced CO, NOx, and particulate emissions as measured in the hot start portion of the FTP heavy-duty transient emissions cycle. A comparison of the emissions response of the two additives shows that the nitrogen in EHN does not contribute to NOx emissions at typical treat rates.