The M48 used large castings for its turret and hull, and these gave the vehicle its characteristic look: the turret was elliptical, and the bow resembled the nose of a frog. M48 had a small, oval driver's hatch and the .50cal M2HB machine gun mounted at the commander's cupola was exposed. The drivers of M48s controlled the tanks through an aircraft-style steering wheel, instead of the single wobble stick control found on the M46 and M47. Early M48s had a Y-shaped muzzle brake, while later vehicles featured a T-shaped design. Late-production tanks also were fitted with an infrared periscope for the driver. One hundred twenty M48 hulls were found to be ballistically deficient, and were therefore used for training only. These vehicles were designated M48C. Short range was a problem for the M48, and four jettisonable 55gal (210L) fuel drums could be mounted on the rear deck to increase the tank's range to about 135 miles (217km).

M48A2 was powered by a more efficient fuel-injected version of Continental's V-12, and when coupled with the extra room for fuel tanks provided by the more compact design of this engine, the range of the M48A2 was greatly increased. The rear of the M48A2 hull was redesigned from a solid plate to one incorporating exhaust louvres, and the hull intake grilles on the each side of the rear deck surrounded a solid center area that was overtop of the exhaust tunnel. The infrared signature of the tank was reduced with this new arrangement. Compare this to M48 and M48A1, where the exhaust was discharged just behind the turret. The engine's air cleaners were also placed in the fighting compartment side of the engine bulkhead for easier maintenance. Suspension components of M48A2 also received an upgrade, since failures were noted in earlier tanks. The compensating idler wheel attachment was modified, a double bump spring replaced the single unit on the first road wheel arm, friction snubbers replaced the hydraulic shock absorbers on the tank. The second and fourth track return rollers were deleted. The driver received a larger steering wheel, and the transmission shifter was moved from behind the steering wheel to the floor on the driver's right. The M48A2 had only one personnel heater exhaust pipe exiting to the left of the roof of the driver's compartment, compared to the exhausts for two heaters on earlier tanks. M48A2 also introduced an improved turret control system, and the tank's fenders were changed from a round to a flat profile.

The 90mm gun tank M48A2C replaced the stereoscopic rangefinder with a more user-friendly M17 coincidence model. M48A2C also used a new ballistic drive which accounted for temperature fluctuations, a larger bore evacuator was fitted to the 90mm gun, and the metric system replaced English measurements as the basis of the tank's fire control system. The auxiliary track tensioning wheels were deleted from M48A2C. One thousand three hundred forty-four M48A2s were modified to M48A2C standard.

The M48A3 modification fitted M48A1s with a diesel engine for greater fuel economy and reduced danger from fuel explosions. The rear deck was reworked to incorporate M60 grilles and exhaust louvres, and rear fender-mounted dry air cleaners were used instead of the oil bath models of the earlier gasoline engines. The auxiliary generator and engine were deleted, since the tank's diesel engine was more efficient than even the smaller auxiliary generator engine. The tank received the suspension upgrades of the M48A2. The personnel heater was changed again, to the type used in the M60, with its characteristic exhaust routed to the right (instead of left) side of the tank. The M48A3's fire extinguisher was improved as well. M48A3 was able to mount a xenon white light or infrared searchlight on the gun shield above the 90mm gun. The gun shield cover was waterproofed, and the crew was provided with a spall liner inside the tank. The fire control system of the M48A3 was also upgraded. The ammunition box for the .50cal MG was reduced from 100 to 50 rounds due to lack of space in the commander's cupola, but conditions were still cramped for the commander.

Bowen-McLaughlin-York, Inc., converted 578 tanks to M48A3 (Mod B) standard starting in 1967. The Mod B tanks differed from the earlier M48A3s by having armor framing running along the tops of the engine exhaust louvres, armor boxes surrounding the taillights, and an adapter ring incorporating vision blocks which raised the commander's cupola by about 5" (13cm). This, combined with a redesign of the cupola door, provided more room for the tank commander. M48A3 (Mod B) tanks also received driver's controls and gauges from the M60A1 tank, the fuel lines were relocated, and the suspension was modified by the addition of knock-out holes for the torsion bars and the redesign of the track return roller mud shields. Detachable headlights were mounted, and the fender telephone intercom was mounted in a higher position. Infrared fire control equipment was installed in the upgraded tanks as well. The upgrades that BMY installed were eventually retrofitted to all M48A3s, and the Mod B designation was subsequently deleted.

The increasing obsolencence of the 90mm gun forced another upgrade project onto the M48A3. M48A5 used the 105mm gun M68 of the M60 tank, and as many M60A1 components as possible were incorporated. The very large M1 cupola was replaced on M48A5s in August 1976 by an Israeli-designed model which was much shorter and used three periscopes mounted around a hatch that could be opened vertically a short distance to grant the tank commander protected visibility. M60D machine guns were also provided for the tank commander (replacing his .50cal machine gun) and loader, and main gun ammunition stowage was increased by 11 rounds to 54. M48A5s with the new features were for a time called M48A5PI (i.e., M48A5 Product Improved), but this designation was later returned to simply M48A5 as older vehicles were upgraded with the new features.

In December 1965, with series production of the 152mm gun-launcher M60A2 expected, it was planned to mount the newly-created surplus of M60 turrets on spare M48A3 hulls. These vehicles were to be called M48A4, however with the limited numbers of M60A2s actually produced, the M48A4 project was cancelled after only a few pilots had been converted.