Product Description
Triumph TR2-5 Top Cover
There are a great number of gearbox top cover assemblies, for overdrive/non-overdrive and the electrical interlock requirements of other equipment.
These types are identified by the quantity and positioning of electrical switches, plus on earlier models the provision of a hole for the dipstick. Conversion of non-overdrive top covers to overdrive type is a matter of drilling and tapping to accept the switch(es) in the correct position(s). This can be done by the owner, or by a machine shop.
Original top cover specifications are as follows:
TR2 to TS5979 with one o/d switch and dipstick hole.
TR2 from TS5980, TR3,TR3A to TS50000 with two o/d switches and dipstick hole.
TR3A from TS50001, TR3B TSF series with two o/d switches but no dipstick hole.
TR3B TCF series, TR4, TR4A with three o/d and rev. lamp switches.
non overdrive TR5, TR250 with top-fitted reverse light switch.
overdrive TR5, TR250 with 3 top-fitted switches.
Selector (inhibitor) switches are best adjusted with the lid off the gearbox. Ideally use a test meter or an illuminated circuit tester (power source, bulb and wires as shown in various workshop manuals) to test for makes or breaks. The further ‘in’ the switch the more resistance to ease of gear change will be felt when the gear-lever is moved from gear to gear. The idea therefore is to screw the switch into the lid the least possible amount to get positive circuit makes and breaks. As the packing washers are thin card, which changes its thickness as it compresses, this can only be achieved by trial and error, and 1 - 3 is the normal range of requirement. Each switch must be adjusted individually. Don't take chances with broken insulation on the switches and/or very loose terminals. There's a lot of 'stripping out' involved to get at a rogue switch which will far outweigh replacement cost (ditto: dodgy wiring).
TR2s, TR3s and TR3As up to TS60000 originally had overdrive switches with screw terminals for the wiring. Later spade terminal switches may of course be used, so long as the ring terminals on the wiring are replaced with Lucar 1/4” wide spade types (part no RTC220A). The switches may require adjustment during the life of the gearbox as the selector forks wear at the top where the switch makes contact. Wear in the gearbox bushes may cause selector fork face wear, which may also cause intermittent overdrive operation. These faulty switch operations will in turn cause the solenoid to chatter and that will certainly cause premature solenoid failure as the points burn out. Reference was made to the switches providing a safety circuit to protect the overdrive. The simple fact is that the unidirectional clutch is exactly that - a unit that works in one direction. It fails very expensively when driven the wrong way, usually destroying the gearbox 3rd motion shaft (or mainshaft) in addition to the whole overdrive. The inhibitor switches are really there to prevent overdrive engagement in reverse.