The engine and gearbox mounting system isolates the drivetrain from the body structure and absorbs vibration. The 1275cc and 1500cc use different mountings, brackets, and fixing arrangements, and there are practical considerations for both that affect the removal and refitting process.
1275cc Mountings
The 1275cc engine sits on a pair of rubber mountings, each carried on a bracket that bolts to the body side, the mounting secured to the engine bearer plate by studs and nuts, with each bracket handed and not interchangeable side to side. The rubber mounts deteriorate over time, particularly if exposed to oil contamination, and should be inspected periodically for cracking, compression set, or separation from the bonded metal plates. When removing the engine, the suggested procedure is to undo the mounting from the engine on the steering-column side, leaving the mounting and bracket on the body, and on the opposite side undo the bracket from the body, leaving the mounting and bracket on the engine, an approach that avoids the difficulty of aligning the engine back into the V-cradle formed by the brackets during reassembly, which can tear the threads on the mounting studs if forced.
Gearbox Mountings
The gearbox is supported by two rubber mountings on a bracket that bolts to the transmission tunnel floor, with a steady bush providing additional lateral restraint, the bracket secured by long bolts passing through the floor. If the gearbox mountings are worn, the gearbox will move excessively under acceleration and deceleration, which can be felt as a thud or knock transmitted through the floor and gear lever. On the 1500, the gearbox mounting arrangement differs from the 1275cc, with the addition of a restraint bracket and bush assembly designed to prevent the gearbox from contacting the transmission tunnel under load. This steady bracket was introduced shortly after the start of 1500 production and was not fitted to the very earliest cars, so owners of early 1500s experiencing a vibration or knock through the floor should check whether this restraint has been fitted, as the repeated impact between the gearbox and tunnel causes damage to both the gearbox casing and the tunnel panel.
1500 Engine Mountings & Maintenance
The 1500 engine mountings are revised to suit the Triumph engine's different mass distribution and mounting points, the brackets being specific to the 1500 and not interchangeable with the 1275cc items, bolting to the bearer plate on the engine and to the brackets on the body sides. Anti-seize compound or copper grease should be applied to all mounting bolt threads during reassembly, as the bolts are in an exposed position beneath the car and will corrode in place if left unprotected, making future removal extremely difficult.
When fitting new mountings, all bolts should be tightened to the specified torque with the weight of the engine resting on the mountings, as tightening with the engine supported on a crane or jack will pre-load the rubber in the wrong direction and shorten its working life.