TR4/4A/5 Model History

From the introduction of the TR2 in 1953, through the TR3 and 3A developments the sidescreen TRs had become highly successful cars on the rally scene for years, with some surprisingly modern features, particularly front disc brakes, first introduced on the TR3 in August 1956. The early cars had the 1991cc wet liner 4 cylinder engine developed from the unit first used in the Standard Vanguard, but by 1959 the TR3A could ordered with the optional 2138cc unit, offering improved torque. By this time work had commenced to come up with a more modern replacement TR model with some creature comforts. Giovanni Michelotti came up with a few prototypes based on the standard or longer wheel base and wider track TR3A chassis. A modified version of one, known as Zoom, was made in glass fibre and formed the basis for the TRS Le Mans cars of 1960/61. Michelotti's task was made difficult since Triumph management took a long time to arrive at a final chassis design for the new car. In 1960 it was decided to keep the standard wheel base TR3A type chassis, but with a four inch wider track and rack and pinion steering. The result was a very appealing body style combining the best features of all the earlier prototypes. This car entered production in July 1961 as the TR4. The body used an optional two piece hard top of which the steel roof panel could be removed, leaving the rear window and surround in place for open air motoring without the buffeting experienced in a full roadster. An optional 'Surrey' soft top and frame could be carried on board in case of showers. It was a further five years before Porsche introduced its Targa top 911 with removable roof panel, although in fairness that top could be carried on board, whereas the large TR4 roof panel has to be left at home! The 2138cc engine was standard on the TR4 but, strangely, the 1991cc unit was offered as an option although few customers ever went for it and it was soon dropped.

Most TR3As of course went to the US and dealers there thought that customers might not like the new car. Production of the old TR3A continued for a further five months after introduction of the TR4 and US dealers persuaded Triumph to make several thousand more such cars in 1962. These were known as the TR3B and used the larger TR4 engine and rack and pinion steering.

Wider than the earlier cars and more purposeful with big Italian looking door handles, full width bumpers front and rear, stainless trim strips on the doors and front wings and broad grill, the TR4 nicely combined Triumph brawn with Italian style. (I must declare an interest here - I have always thought the Michelotti body style to be the most attractive of all the TRs.) The cockpit is more inviting that that of the earlier cars, with wider, more enveloping seats, more room in the footwells and wind up windows, the first on any Triumph sports model. In addition the TR4 was the first European car to have face level ventilation, beating the Ford Cortina Mk I by a full 12 months. Switchgear was considerably tidied up with indicators controlled by a steering column stalk, as is the optional overdrive. On the roadster version the hood was easier to operate, with a foldaway frame and with the hood down the higher doors make the car less wind-blown. The wraparound screen helps too, offering better protection against sudden showers and with the hood up it's much less draughty than a TR2-3. The hood design came in for praise in period with Gregor Grant finding it completely waterproof on the car he drove in torrential rain on road test for Autosport magazine. However, to run a TR4 roadster with the hood down it first has to be removed from the frame, which then folds down under three flip-over vinyl panels to form a backrest for the vestigial rear seats. The hood itself is stored in the boot. The TR4 retained the fly-off handbrake of earlier TRs but incorporated a brace between the floor and dashboard, reducing the scuttle shake and body dither which could plague sidescreen models. The wider track and optional front anti-roll bar provide enough control without making the suspension too stiff. As for the drive train, the TR4 was the first of the line to have synchromesh on all gears.

Four years into the life of the TR4 came the most significant upgrade since the TR2 was introduced: independent rear suspension for the TR4A, introduced in January 1965, although the new model was also built with a live axle for the US market. A revised chassis design was required to accommodate the IRS and there were some small changes and refinements to the front suspension. The electrical system was converted to negative earth, a new design of steering rack was fitted together with a revised front bumper with shorter overriders and a revised grill. A new globe' bonnet medallion replaced the TR4 badge and the front side lights were now housed in units on the wings, together with indicator repeaters. A wood veneer dashboard replaced the painted metal of the previous model. The handbrake was repositioned on top of the transmission tunnel from the right hand floor and, although this was welcomed by long-legged drivers, the loss of mechanical advantage from the necessarily shorter lever meant that the handbrake struggled to hold the car on steeper gradients. There are mods to address this. A new radiator with a closed circuit system was fitted together with a new exhaust system and a diaphragm spring clutch. As regards weather equipment the TR4A has a combined hood and frame, which folds into the space behind the front seats. This is a more convenient arrangement than on the TR4, but it does render the rear 'seats' unusable for anything but stowing a small amount of luggage.

The TR4A chassis is not as robust as that of the TR4 and more prone to corrosion. It is important to check that the lower wishbone mounts for the front suspension have been reinforced. These were prone to pull away from the chassis even when the cars were new. It is also worth changing from single to a two stud fixing for these mounting brackets. The rear outriggers that carry the rear suspension trailing arms are also corrosion prone and the trailing arm mounting brackets should be examined for cracks. The rear spring mounting/diff carrier can also give problems with diff mounting pins pulling through or away from the metal. In bad cases the spring abutment can bend upwards at both ends, reducing the effectiveness of the coil springs and causing the rear end to sag. Any prospective purchase should be critically examined in these areas. Remember also that the whole body is a rotter also. My TR4A was less than four years old when purchased by my late father but rust could already be seen bubbling through both rear wings in front of the rear light clusters. These cars were built when little was known about automotive rust proofing and at a time when the British motor industry depended on built in obsolescence for survival, few in the 1960s would have expected so many to still be on the road over 50 years later! Floors collect rainwater and rust inevitably follows. After driving through heavy rain it is worth lifting the carpets/underfelt to check and if they are wet remove them and dry thoroughly before replacing. Try to identify how the water is getting in and fix the problem. Carefully check the front edge of the bonnet, the rear valance and the lower corners of the boot lid, Check along the tops of all four wings and the adjacent areas of the body, the rear trailing edges of the front wings, the door bottoms and the lowest part of the windscreen frame, where it meets the scuttle – this area is difficult and expensive to repair properly. Check the lower rear corners of both front wings, water gets into these areas both from the drain holes in the inner wings, just behind the bonnet bump stops, and from the heater plenum chamber and the designers just relied on the tiny gaps between the sills and the bottom of the wings for the water to drain out. If replacement wings are fitted be sure to fit wheel arch protectors to preserve them. The rear wheels throw water, mud, and, in winter, road salt up inside the wings where the muck lodges behind the rear lights and simply festers, accounting for the issue with my car mentioned earlier. The TR4 did not have seat belt mountings, although they were introduced for the 4A. If necessary it is not difficult to install suitable brackets in a 4 to accept either static or inertia-reel harnesses.

Mechanically speaking the TR4 and 4A engines are long lived and reliable with no specific vices. Check for untoward noise and oil and coolant leaks and also that, when fully hot, the engine generates and maintains an oil pressure of at least 70psi at 2,000rpm. Be aware that even new these engines are a little tappety and even with the most careful clearance adjustment (0.010" cold for both inlet and exhaust) you will never eliminate all top end noise. Should you ever have cause to remove the cylinder head on one of these cars be sure to clamp the cylinder liners in place, otherwise if the crankshaft is inadvertently turned by even a few degrees the figure of eight gaskets below the liners, which prevent coolant entering the sump, will be disturbed and the liners will have to be removed and new seals installed. For the same reason, when removing the cylinder head do not be tempted to break the head to block seal by turning the engine to let the compression do the work, tap the head gently with a hard plastic hammer. For engine longevity I recommend an oil and filter change at 3,000 mile intervals - use a good quality 20W50 year round. Seek out one designed for classic engines with a decent level of ZDDP to protect the cam followers. I use Classic Oils Heritage 20W50 and find it keeps excellent oil pressure however hot it gets. The all-synchromesh gearbox on the TR4/4A is equally reliable, make the standard checks for noise and jumping out of gear when the throttle is suddenly snapped shut though the most likely problem, unless the unit has been run with little or no oil, is wom or damaged layshaft bearings, these can be replaced by the heavier duty type as used in the Stag box. The optional 'A' type Laycock de Normanville overdrive, operating on 2nd, 3rd and top gears, carried over from the TR4, is a highly desirable and useful extra. Make sure it cuts in and out promptly. If it fails to operate it could be a simple electrical problem, there are several bullet connectors in the circuit and one of these can come adrift (it happened on my car). If overdrive cannot be disengaged then the operating solenoid may well be stuck. This should be investigated immediately since overdrive will be permanently engaged and expensive damage will result if the car is reversed in this condition.

The TR4's live rear axle is very robust and, like the gearbox, should be trouble-free unless it has had past abuse. The IRS diff however leads a hard life due to the complexity of the drivetrain and can suffer badly from shock loadings generated by worn UJs and mounting rubbers. The outer UJs are very difficult to grease in situ so are frequently neglected. The sliding joints of the IRS driveshafts are another source of play and some fit replacement after-market CV type driveshafts from preference. Check that the final drive casing is not loose on its mounting pins, either because the pins have pulled out of the rear spring mounting or because the rubber mountings have been softened by leaking oil. Rubber mountings can usefully be replaced by uprated polyurethane ones, which are oil resistant. Check the six studs which retain the hub and brake back plate to the trailing arm, very often the threads will have stripped in the soft aluminium due to nuts having been over-tightened (the correct torque figure is only 12-14 lbs ft.). If this has happened the threads should be helicoiled.

Overall the TR4 and 4A were well developed cars, adopting the well proven engine and drive train of the TR2 and 3 models and are generally fault free. This also accounts for the fact that changes during the production run of the 4 and 4A were both few and trivial. The engines are very robust and thrive on hard use. Properly maintained and sympathetically handled (with 5000rpm strictly observed as the sustained rev limit) they can be expected to reach a six-figure mileage before requiring attention.

Enter the TR5 While the TR4 was being developed there was a proposal to convert the old 2138cc engine to 2.5 litres by discarding the wet liners and designing a new conventional block with a 92mm bore, but the project was dropped. However, the long term wish to put a 2.5 litre engine in a TR remained and after 15 years of the old 4-cylinder wet liner slogger the market was crying out for more power. It seemed logical to develop the 6 cylinder Triumph 2000 saloon engine for this purpose. Such an engine in a TR was not a new concept, even in TR3A days there had been development cars running with tuned versions of the then Vanguard Six engine installed. The 1998cc Triumph 2000 engine produces 90bhp in standard form, 14 fewer than the TR4A unit, and has considerably less torque. Triumph wanted at least 125bhp and more if possible. Without stretching capacity this power could be achieved only by tuning out most of the flexibility and reliability of the 2000 unit. Bore spacing ruled out a bigger bore so there had to be a stroke change. The six cylinder engine was a development of the original Standard 8 4 cylinder 800cc engine. The stroke had been 76mm during the engine's 15-year run. Stretching capacity from 1998 to 2498cc involved a stroke increase to 95mm. The unfashionably long stoke gave tremendous torque but not a great deal of power on carburettors. The TR5 engine uses a completely new cylinder head, first 'blooded' in the fuel injected Triumph 2000 that ran in the 1966 British Saloon Car Championship. Triumph were at first drawn to using fuel injection on the TR5 as it was thought its more precise metering might be needed to comply with North America's new exhaust emission regulations but it was then realised that it would also be able to tame a very wild camshaft liberating useful extra power whilst retaining docility and an acceptable idle. Consequently Lucas Mark 2 mechanical fuel injection was added to the TR5 engine as a perfect solution to boosting the power to a healthy 150bhp. The Lucas Pl system derived directly from that fitted to the 1957 Le Mans winning Jaguar D type and the Mark 1 forms fitted to some production Maseratis. The TR5 represented the first application of fuel injection on a UK production car. From the tank fuel is drawn through a paper element filter and pressurised to 100psi by a motor driven fuel pump. On the first few TR5s this pump was in the engine compartment but to keep it cooler production cars had it in the boot, alongside the filter to the side of the fuel tank behind a trim panel. Pressurised fuel is led to the metering unit, in which a rotor is driven from the distributor shaft. Fuel is then metered to individual injectors in amounts decided by the mixture control unit mounted integrally with the metering distributor. Control is achieved by a mechanism that responds to inlet manifold vacuum and the throttle opening. There is provision for extra fuel for cold starts. The 2.5 litre engine was a remarkable development from the worthy Triumph 2000 unit that preceded it. Compared to its predecessor, the TR4A, maximum power was up by nearly 50% and torque by 35% and yet the engine weight was down by almost 3kgs. The well proven all-synchro gearbox was unchanged with overdrive continuing as an optional extra, operating on 2nd, 3rd and top as on the 4/4A. However, allowing for the greater torque of the six-cylinder car it is as well not to make too enthusiastic use of old 2nd at full throttle! The final drive and driveshafts were beefed up to cope with the extra torque and the final drive ratio is 3.45:1 (3.7:1 on the 4 and 4A) it also has new chassis mountings, although these remain prone to tearing from the chassis due to the higher torque so still need a careful check. A brake servo with integral master cylinder and reservoir is now standard. The suspension is basically like that of the 4A, though the trailing arms are modified to accept revised and stiffer rear springs and give adequate clearance for the wider 4.5J wheels. The chassis frame is almost identical to the TR4A although there had to be changes to the bracing tube between the front turrets to accommodate the longer engine and new brackets for revised engine mountings. The Michelotti TR4/4A bodyshell, familiar since the autumn of 1961, was retained virtually unaltered for the TR5. Styling touches to identify the new car are the new, partly black-painted grill, fatter stainless strips along the side body crease and a TR5 badge on the bonnet. There are 2500 badges and indicator repeaters on the rear wings and twin reversing lamps under the boot lid are now standard. There is a TR5PI badge on the boot lid. There are big changes in the instrument panel and facia layout. The speedo, rev-counter and minor instruments are redesigned with black bezels to eliminate windscreen reflections at night and the wiper and washers are now operated by rocker switches, all set in an attractive wood facia with a matt finish. To comply with US safety regulations the starter, choke and heater switches are more deeply recessed into a padded surround and the steering wheel has padded spokes. The hood mechanism has been revised to include rigid cantrails above each door glass, the hood being attached to these by Velcro strips. This hood was widely praised in period as one of the best available on a medium priced sports car. The sponge rubber edges of the rigid side rails bear hard against the tops of the frameless side windows, forming a seal as secure as in most saloons. The hood can be raised or lowered by one person in seconds and is secured to the top of the screen by recessed levers, much safer than the clamps on the TR4/4A. The hard top TR5 retains the detachable roof panel and the Surrey top and frame remain optional. An unusual styling touch was the adoption of imitation 'Rostyle' wheel trims, complete with dummy wheel-nuts, although wire wheels remained as a factory option. For some reason an original set of these wheel trims commands a king's ransom these days. Unfortunately the Lucas fuel injection could not be made to operate with sufficient precision to meet the new US emission laws without the addition oif expensive extra controls. For this market the new car had a modified version of the 2498cc 6-cylinder with twin Stromberg 175CD carburettors, a milder camshaft and a lower compression ratio of 8.5:1, rather than the 9.5:1 of the fuel injected car. As a result the earlier 3.7:1 final drive ratio was retained. This US model was known as the TR250 and whilst it was more refined than the TR4A the emasculated engine gave no more power than the earlier car so performance was much the same.

The TR5 was almost the end of the line for separate chassis TRs. By the late 60s this method of construction was showing its age and just as all the earlier models the TR5 was criticised for scuttle shake and creaks from the chassis over really rough roads. However, with the hard top firmly bolted in place torsional stiffness is much improved and the car will feel more 'together' and handle with aplomb.

Production of the TR4A ended in July 1967 and TR5s started rolling off the line just one month later but was destined to last only until September 1968. With the shortest production run of any TR model and combining as it did stylish Italianate looks with the extra poke of a fuel injected '6' the TR5 was always destined to be the most sought after TR and prices now reflect this. Any prospective purchaser must be on their guard against converted TR250s or TR4/4As cloned by the unscrupulous and passed off as original UK RHD TR5s.