I am originally from Alaska and drove my 94 Explorer from there to Arkansas a few years back. I've owned several 91-94 Explorers.
The 91-94 Explorer is a very solid vehicle. A lot of them are abused, however, so find one that has been well kept and maintained. An Alaskan rig will likely still have good paint and weatherstrip though, the climate is easy on them in that regard. Do watch out for rust though. The rocker panels are the main spots that rust.
There are two main weaknesses.
1. Stock cylinder heads on the motor are defective casting and usually develop small cracks, often before 100K miles. It's never "just a head gasket", the only permanent fix is a new set of aftermarket (not remanufactured) cylinder heads. The rest of the motor is good for 500k miles. Try to find out if the heads have been replaced and check casting numbers. Valvetrain wear is common resulting in valvetrain noise but does not hurt the motor. 93-94 models have a little more power, but also have a couple more sensors to maintain.
2. Transmission. The manual trans (M5OD) is a safe bet and while not heavy duty will last a long time if not abused. The automatic trans (A4LD) is under-cooled for most climates but in Alaska they last longer. The stock cooler is not adequate for southern states and stop-and-go traffic will quickly overheat the trans. The transmission is not strong enough for towing beyond very light trailers. If you find a good transmission that hasn't yet been rebuilt (look for under 160k miles) you can extend its lifespan with an improved fluid cooler, add a shift correction kit and Sonnax upgrades, and monitor it with a trans temp gauge. PATC in Texas makes an upgraded complete transmission and sells individual upgrades, and TransmissionPartsUSA.com sells all the necessary parts to service and upgrade it yourself. You can do a valve body rebuild and do upgrades yourself, and it's not hard. The transmission had the most factory upgrades in 94, so 94 is the best year in terms of transmission. Keep in mind that many transmission shops don't know how to rebuild the A4LD worth a damn; I have never had a good experience with a rebuilt A4LD.
The 4.0 motor is reliable and has good torque. It does not make a lot of horsepower but will run forever. Do not expect to tow with it or win races. The Sport/2-door models can move pretty quick if they are low power option models, due to the lighter weight. There are not a whole lot of performance parts for the 4.0 but there are some such as headers and cams. It will take some money to make the 4.0 produce more power but the key benefit of this motor is reliability. The cooling system is reliable. The fuel injection system is reliable as well, though it is OBD-I (EEC-IV) so don't expect advanced diagnostic support. Fuel economy typically ranges from 14-18mpg depending on vehicle weight and driving habits. My 94 2dr 4x4 gets 16mpg no matter what.
Do check if the fuel pump has been replaced on a high mileage Explorer. The stock pump can last a long time or a short time, depending on the habits of the previous owners. Regular fuel filter replacement and keeping the fuel level above 1/4 is best for pump lifespan. If the fuel filter isn't ever changed and the truck is often running on fumes (the pump is cooled by the fuel it is submerged in) then the pump won't last.
The suspension design is solid. Clunky suspensions are usually radius arm bushings, which are not a hard fix, though on some models you may have to remove some frame bracket rivets and replace them with bolts. A cheap fix. The rear suspension design generally needs no maintenance.
Rear axles are a strong 8.8 design, with factory limited slip differentials on many models. Several axle ratios were available so check the door tag for the axle code when buying an Explorer; higher ratios such as 3.73-equipped models will be easier on the transmission than 3.27 or 3.08 models. Front axles are a TTB (Twin Torsion Beam, a cross between solid axle and IFS) Dana 35 with Dana 44 parts. Front axles are very strong. Factory manual locking hubs are made by Warn and very strong. Factory automatic locking hubs are weak and often are broken, but for around $200 you can put new strong manual locking hubs on.
Transfer cases are the Borg Warner 13-54, available in lever shift and electronic shift. Both transfer cases are very strong and should last the life of the vehicle. The lever shift model has no weakness, though some high mileage models can wear out the shift pads which requires replacement (not hard to do). This is evidenced by a grinding noise from the transfer case. Electronic (push-button) shift models are more common and don't have this issue, but the shift motor has a stop bushing that deteriorates over time. The failure of this bushing causes the transfer case to get stuck in 2WD usually, with the shift buttons having no effect. It is easy to access and rebuild - if you can rebuild a power window motor, you can rebuild the shift motor. The bushing can be made out of a small chunk of tubing.
93-94 models are usually equipped with R-134a refrigerant air conditioning. If the system needs service then you don't need to change much. The 91-92 models use R-12 refrigerant, so if the AC is nonfunctional it may need to be retrofitted with all new gaskets and compressor to accept the R-134a refrigerant (R-12 is not sold now).
Steering components usually last a long time on these trucks. The steering box is a standard Ford unit as is used in full size pickups. It has an adjuster that can take some slack out of the steering. They seem to respond best to the use of Ford Type F transmission fluid. You can use standard power steering fluid, but it tends to leak more.
Electrical systems on these trucks are very reliable and wiring doesn't have issues. However, the battery cables can develop internal corrosion leading to no-start issues. It is an easy fix and not real expensive. Power windows that don't work are usually due to crumbled window regulator bushings, which are in the window motor. They are inexpensive and not hard to replace, takes about 20-30 minutes per window.
Parts for the Explorer are very affordable and readily available. It is getting harder to find Explorers in junkyards so don't expect to easily find replacements for damaged interior parts. Ebay has some though, and the more common ones like door handles are still produced.
Expect to pay between $1000 and $2000 for a good Explorer. They don't hold a high value due to their age and the whole "rollover controversy" which was mostly BS. With a few preventative fixes, these trucks are tough as nails and very practical. 4-door models are easy to drive and hold a lot of cargo, 2-door models can be VERY fun to drive in snow/ice and are a bit quicker. I will say that my 2-door 4x4 model is still the best winter vehicle I've driven. It is capable on and off-road, and on ice/snow something about the wheelbase makes it a perfect handling vehicle that you can hang the tail out if you want and powerslide with ease and control. Even on dry pavement the 2-door models can really corner with the right shocks/springs/tires.
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