Manual transmission lubricants with improved synchromesh performance

Abstract

A lubricant comprising (a) an oil of lubricating viscosity; and (b) an overbased, carbonated calcium arylsulfonate detergent having a total base number (TBN) of at least about 640 as calculated on an oil-free basis effectively lubricates the surfaces in the synchronizer of a manual transmission.

What is claimed is: 
     
         1 . A method of lubricating a non-sintered metal-based surface in the synchronizer of a manual transmission, comprising supplying thereto a lubricant comprising:
 (a) an oil of lubricating viscosity; and   (b) an overbased, carbonated calcium arylsulfonate detergent having a total base number (TBN) of at least about 640 as calculated on an oil-free basis.   
     
     
         2 . The method of  claim 1  wherein the synchronizer has at least one surface of brass, bronze, or a molybdenum material. 
     
     
         3 . The method of  claim 1  or  claim 2  wherein the synchronizer has at least one surface of solid brass or solid bronze. 
     
     
         4 . The method of any of  claims 1  through  3  wherein at least one lubricated non-sintered metal-based surface in said synchronizer is brass. 
     
     
         5 . The method of any of  claims 1  through  4  wherein the carbonated calcium arylsulfonate detergent has a TBN of about 650 to about 1000. 
     
     
         6 . The method of any of  claims 1  through  5  wherein the arylsulfonate detergent comprises an alkylarylsulfonate anion in which the alkyl group is linear. 
     
     
         7 . The method of any of  claims 1  through  5  wherein the arylsulfonate detergent comprises an alkylarylsulfonate anion in which the alkyl group is branched. 
     
     
         8 . The method of any of  claims 1  through  7  wherein the arylsulfonate detergent comprises an alkylarylsulfonate anion in which the alkyl group contains about 12 to about 36 carbon atoms. 
     
     
         9 . The method of any of  claims 1  through  8  wherein the arylsulfonate is an alkyl-substituted benzenesulfonate or an alkyl-substituted toluenesulfonate. 
     
     
         10 . The method of any of  claims 1  through  9  wherein the amount of calcium in the lubricant is about 0.03 to about 1.0 weight percent. 
     
     
         11 . The method of any of  claims 1  through  10  wherein the amount of the overbased, carbonated calcium arylsulfonate detergent in the lubricant is about 0.14 percent to about 4 percent by weight. 
     
     
         12 . The method of any of  claims 1  through  11  wherein the amount of the overbased, carbonated calcium arylsulfonate detergent in the lubricant is about 0.14 to about 3 percent by weight 
     
     
         13 . The method of any of  claims 1  through  12  wherein the lubricant further comprises an overbased phenate detergent. 
     
     
         14 . The method of any of  claims 1  through  13  wherein the lubricant further comprises an overbased magnesium sulfonate. 
     
     
         15 . The method of any of  claims 1  through  14  wherein the lubricant further comprises a dialkylphosphite. 
     
     
         16 . The method of any of  claims 1  through  15  wherein the lubricant further comprises a succinimide dispersant which has been treated with at least one of a borating agent and terephthalic acid.