TR4AFollowing on from the TR4, the TR4A brought with it not just styling changes, but a radically different chassis and an uprated engine to 104BHP.
This chassis was designed to accept the new semi-trailing arm independent rear suspension. Having 6 universal joints, 3 prop shafts and 2 trailing arms, the system was appreciatively more expensive then the previous live axle arrangement. This lead dealers in the USA to react uncomfortably to the new design on cost grounds.
To appease the US Dealers, Triumph built the TR4A in two forms, one with a live axle primarily for the US and the TR4A IRS for other markets where the price was less sensitive. The US dealers eventually saw sense; taking the IRS cars and condemning the adapted live axle cars to the history books.
Other Major changes were the better cylinder head with more power, new exhaust, new grill, side lights and chrome trim along the door/wings, wooden dash and better seats. The hood too was revised with proper catches at the front, which ensured it would stay on, unlike the pitifully poor TR4 hood.