The biggest news is the arrival of a new eight-speed automatic gearbox, which brings CO2 emissions down to a competitive 198g/km for both the 188bhp diesel (available exclusively in a new entry-level Laredo trim), and the more popular 247bhp version.
A V8 petrol SRT8 model is due to follow, although this will appeal only to the very extravagant.
The revised Grand Cherokee gets sharper exterior styling, including LED running lights, while the interior has been freshened up with digital driver readouts and an 8.7-inch touch-screen.
There are five trims: Laredo, Limited, Limited Plus, Overland and Summit.
Laredo and Limited models ride on steel springs and have a four-wheel-drive system that can send up to 100% of the engine's torque to either the front or the rear wheels, depending on available traction.
Pricier Overland and Summit versions get air suspension and a more sophisticated four-wheel-drive set-up that uses torque vectoring to shuffle power between individual wheels as needed.
All diesel Grand Cherokee models come with a low-ratio gearbox and a 'Selec-Terrain' system that allows you to optimise the car's electronics for different types of terrain.
What's the 2013 Jeep Grand Cherokee like to drive?
The new eight-speed automatic gearbox is much better than the five-speed 'box it replaces. The closer ratios and silky changes allow you to make smoother progress, and kickdown is also sharper when you ask for a sudden surge of acceleration.
There is a Sport mode, but this is barely worth using. It makes the gearbox hold on to ratios for longer and only serves to highlight how clattery the diesel engine becomes at high revs.
In fact, even with the gearbox in its standard setting, the Grand Cherokee is far from the quietest big SUV. Substantial engine noise enters the cabin at motorway speeds, or even under moderate acceleration, although neither wind nor tyre noise are too much of a problem.
Our initial international drive highlighted the old-school feel of the models with steel springs; they suffer from lots of wallowing body movements that discourage any thoughts of going around corners quickly.
The ride could also be better, because it becomes jarring over sharper bumps and never feels fully settled.
Our UK drive was restricted to air-sprung Overland and Summit models, and these do a better job of controlling the car's considerable weight. That said, the Grand Cherokee still isn't as sharp to drive as a BMW X5, and the damping isn't effective enough to make the ride truly comfortable.
There's still plenty of body float on undulating roads, too, and the steering is slow.
All of this doesn't mean the Grand Cherokee is unpleasant to drive; in unhurried cruising it's relaxing enough. However, on any remotely taxing road, it feels decidedly cumbersome.
What's the 2013 Jeep Grand Cherokee like inside?
The spacious interior has been thoroughly modernised. The big new touch-screen is simple to use and brightens up the whole dash, while a colourful, crisp readout now displays a digital speedo and rev-counter, plus a mind-boggling array of extra info, from weather conditions to fuel economy.
However, there are still some cheap-feeling materials in the cabin, so the Grand Cherokee lacks the sense of exacting quality that most people buying in this class will expect.
Rear space remains unchanged, which means there's plenty of leg- and headroom. The boot is big, too, at 782 litres, although it's a shame the load floor is high and there's no option of a third row of seats.
All Jeep Grand Cherokee models come with dual-zone climate control, automatic wipers, USB and auxiliary inputs, and roof rails.
The Limited trim option has front and rear parking sensors, a rear-view camera, leather upholstery, a powered tailgate, electrically adjustable and heated front seats, plus a stereo upgrade, while the Limited Plus adds sat-nav and 20-inch alloys.
The Overland is even more generously equipped, with a panoramic sunroof and extra safety features, including a blind-spot monitor and adaptive cruise control with forward collision detection.
The range-topping Summit gets a 19-speaker Harman Kardon stereo, along with various style upgrades.
Should I buy one?
There's still a certain charm to the Grand Cherokee, and the new automatic gearbox has made Jeep's butch-looking SUV more pleasant to drive and more fuel-efficient than ever before.
It's still a formidable off-roader, too, and is undoubtedly cheaper spec-for-spec than almost all of its rivals.
Yet, for all this, the Grand Cherokee feels too far off the pace when it comes to on-road composure and interior quality, while many of its rivals offer extra seating capacity.
With an entry-level TDV6 version of the impressive Range Rover Sport arriving in September, and a new BMW X5 with dramatically reduced CO2 emissions following in November, things are only set to get tougher for the big Jeep.
By Rory White and Vicky Parrott
What Car? says...
Jeep Grand Cherokee Overland
Engine size 3.0-litre diesel
Price from £36,995
Torque 325lb ft
0-60mph 10.2 seconds
Top speed 119mph
Fuel economy 37.7mpg
Jeep Grand Cherokee Summit
Engine size 3.0-litre diesel
Price from £38,995
Torque 420lb ft
0-60mph 8.2 seconds
Top speed 126mph
Fuel economy 37.7mpg