You can quickly confirm by simply looking at the transfer case. On the backside of the case (opposite the front output shaft) should be a round tag about 2" across, held on by a single screw. For "Model," it should read either "231J" or "242J" - the "J" stands for "Jeep." Both transfer cases were produced with various input/output setups and a couple different gear ratios, as well as other internal changes - so a Chevvy case would say "231C," a Dodge case "231D" or "231HD" (Heavy-Duty Dodge,) &c.
Engines are going to be either the AMC 150cid I4 or AMC 242 cid I6. I do not believe the Renault 126cid Turbo Diesel I4 was available in 1988.
Automatic transmission will be the AW4 (a very solid slushbox!) while a manual gives you a couple of options -
A150 will have either an AX-4 (four-speed) or AX-5 (five-speed)
A242 will have the Peugeot BA-10/5 (OEM) or AX-15 (if swapped.) The two can be differentiated visually by checking for a longwise split down the length of the case - if you have that split, it's a Peugeot (and start looking for an AX-15. I've been through a few of these...)
Front axle will be a Dana 30. Gearing will likely be either 3.54:1 (AW4) or 3.08:1 (any manual.) Rear can be either a D35 (fairly standard) or D44 (Heavy-Duty and Trailer Tow Package.) The D44 can be picked out of a crowd by its roughly hexagonal shape, and the slight "point" toward the bottom of the cover. The D35 has a cover that is more nearly oval. Rear gearing will match the front.
If you have a five-speed stick, you will note an increase in fuel efficiency if you do not use fifth gear for anything less than, say, 80mph. The axle gearing just isn't there. The 3.54's used with the AW4 match up to the transmission gearing much better, I've not noted any trouble with those.
And, FYI, you have the "RENIX" (RENault/bendIX) control system. Mods are fairly rare, but it's as reliable as your average brick. Controls are made by Bendix/King, and most sensors and ancillary parts are GM (or other standard.)
Watch for leakage at the body seam on the fuel injectors. The RENIX units are metal crimped to plastic, and tend to leak at that crimp. If you note a leak in one, replace all six so you don't have to worry about it later. 19# or 20# units for Small Block Ford or Small Block Chevvy (reports from the field are good on FiveO Motorsports units) will serve neatly, and cost you rather less than OEM replacements. Be sure the new injectors come with new O-rings, and you'll also want to go to the dealership to get fuel line quick-connect renewal kits (two O-rings, a Nylon spacer, and the Nylon clip.)
If you have the AW4, do not use ATF +4 (the ChryCo stuff,) and a change to synthetic fluid is not advised.
5-90
