By David Porter, Customer and Technical Support at The Bonneville Shop
Is countershaft sealing the issue? We are often times confronted with mysterious leaks and are confounded by trying to establish the origin of the misplaced oil. Triumph issued a service bulletin in 1973 pertaining to a leak occurring through the splines on the mainshaft high-gear.
Triumph issued a Service Bulletin on 10/23/73 pertaining to a leak occurring through the splines on the mainshaft high-gear.
At the time, prior to the fitment of an o-ring on the 5-speed high-gear splines, the solution was to inspect and clean all of the oil from the splines and countershaft sprocket. After fitting the sprocket onto the splined high-gear, the mechanic was instructed to apply a bead of sealant around the base of the countershaft, install the tab washer, then tighten the nut down. This would form a seal around the interface between the sprocket and splines, thus preventing oil leaks, at least temporarily.
Curiously, this Service Bulletin on countershaft sealing, dated 10/23/73, appeared during the 1974 model year production run. The 1974 TR7RV and T140V models were fitted with an o-ring, 71-1070, between the countershaft sprocket and tab washer, effectively shttps://www.ebay.com/itm/400396660137ealing the high-gear splines.
There is no mention of the 71-1070 o-ring in the 1973 parts book, although it was undoubtedly a known solution, as the 1974 Triumph 750 Replacement Parts Catalogue was published June, 1973. For our purposes, this technical tip will help slow the leaks from both the 4-speed and 5-speed models prior to the 1974 model year.
