Code named Zest during development, the new TR4 by Michelotti did away with the cutaway door design of the previous TRs to allow for wind-down windows in place of less convenient side-curtains. The angular rear allowed a boot with considerable capacity for a sports car. Advanced features included the use of adjustable fascia ventilation, and the option of a unique hard top that consisted of a fixed glass rear window (called a backlight) with an integral roll bar and a detachable, steel centre panel (aluminium for the first 500 units). This was the first such roof system on a production car and preceded by five years the Porsche 911 Targa, which has since become the generic name for this style of top. On the TR4 the rigid roof panel was replaceable with an easily folded and stowed vinyl insert and supporting frame called a "Surrey top".

The pushrod Standard inline-four engine used in the earlier TR2/3 models, was designed for use by the Ferguson TE20 tractor. The TR4 continued to use it, but the displacement was increased from 1991cc to 2138 cc in the TR4 by increasing bore size. Gradual improvements in the manifolds and cylinder head allowed for some improvements culminating in the TR4A model. In 1965, the TR4A with IRS or independent rear suspension superseded the TR4.

Visually similar to the TR4 roadster it was derived from, the TR5 replaced Triumph's Standard inline-four engine with the much more powerful Triumph 2.5-litre straight-6 with Lucas mechanical fuel injection and delivering 150 bhp. Price pressures and tighter emissions standards in the U.S. resulted in a much less powerful carburettor version, the TR250, being sold on the North American market.

The TR5 was produced in small numbers when compared with either the TR250 or the later TR6, with just 2,947 units produced; the first car was assembled on 29 August 1967 and the last on 19 September 1968. Of these, 1,161 were destined for the UK market, the remainder were left hand drive and were exported to France, Belgium and Germany amongst other countries. In the first quarter of 2011 there were approximately 410 licensed and 74 SORN TR5s registered with the DVLA

The TR6 was launched in January 1969, production having begun several months earlier, production continued until July 1976. Of the 91,850 TR6s produced, 83,480 were exported, almost all of them to the United States, while only 8,370 were sold in the UK. The body was styled by Karmann of Germany. There were some changes from the TR5 but the same chassis, engines, running gear, doors, windscreen, and much of the body tub were taken directly from the TR5. The new removable hardtop for the TR6 was designed in-house by Triumph, and was available as an option. Construction was traditional body-on-frame with four-wheel independent suspension, front disc brakes and rear drum brakes, all the cars were powered by Triumph's 2.5-litre straight-6 engine.