Just a few pointers:
All MJs were built as a full unibody design with the body and frame rails tied/welded together as one piece and cannot be removed.
Don't forget to mention that the rear is a fully boxed frame with the bed bolted to it. The bed is removable.
Also, the "uni-frame" is stronger than an XJs.
Also, most MJ's through all years are equipped with a height sensing proportioning valve that is used to change the bias of the brakes if the bed had a load in it.
*ALL* MJs had this, not most.
Comes in longbed or shortbeds two-tone versions (some equipped with the AMC internal roll-bar).
What the heck?!? Internal rollbar? That's pure fantasy there. Don't forget to mention that all 86 models are longbeds.
Long bed versions come with a larger gas tank than the short bed and is located front of the axle.
113.5" shortbed (16 gal tank)
119.9" longbed (18 gal [longbed, opt shortbed] 23.5 gal [opt longbed])
The standard long bed tank in 86-88 is 16 gal. Optional one is 23.5 gal and that became the standard longbed tank in 89. The shortbed tank is 18 gal and that is the only tank available with the short bed.
Gauge cluster during 86' have mechanical-powered gauges. On 87-90 gauges, The speedometer uses a cable, but all gauges 91-92 use a computer cable.
84-86 XJ/MJ have a different mounting clip between the speedo cable and cluster, but the guage clusters do interchange with 87-90 if you swap clips. 91-92 are indeed electronic and do not interchage with 86-90.
I know this one sounds especially nit-picky, but all my dealership brochures state:
short bed 2wd=113.1 4wd=112.9
long bed 2wd=119.6 4wd=119.4
2.5L I4 TBI (fuel injected) - 117 hp @ 5000 rpm, 135 ftlb @ 3500 rpm - used in 86 and updated in 87-90 to 121hp
Don't forget that the 2.5L became MPI in 91 and was rated for 130hp@5250 and149 ftlb@3250
4.0L I6 EFI "Power Tech" - 177 hp @ 4750 rpm, 220 ft lb @ 4000 rpm - used 87-90
4.0L I6 MPI "Power Tech HO" (High Output) - 190 hp @ 4750 rpm, 220 ft lb @ 4,000 rpm - used in 91-92
And not that it matters cause I can't find my 87 brochure, but the 4.0 was actually rated for a bit less than 177 in '87. I'll update as soon as I find it.
AW4 - 4 speed automatic, electronically controlled - manufactured by Aisin - used from 86-92 (87-92 models include a Power/Comfort button that adjusts the shift points, also known as a towing package; all transmissions with the towing package came with a transmission cooler and 3.73 gears stock)
I can find absolutely no evidence of 3.73 gears ever coming in an MJ. That was an XJ thing (and pretty rare at that). The AW-4 came into the picture in the 87 model year, not 86. My 88 brochure mentions that the "power" side of the power/comfort button is for offroading and makes no mention of using it for towing. As far as I can tell, the "tow package" you speak of was a dealership-installed "trailering package" and consisted of a hitch and trailer plug harness, that's it. It was available with any MJ, although 86 seems limited to class 1 and 2 hitches. The "Metric Tonne" or "Big Ton" or "payload package" was designed for hauling, was only available on longbeds, and consisted of an AMC-20 rear axle in 86, Dana 44 rear axle in 87-92, heavier duty springs front and rear, tougher shocks, the larger tires, fullsize spare and 15x7 wheels. In the AMC-20, the only gear ratio was 4.10, Dana 44s got stuck with the standard ratio available with the specified drivetrain combo (3.08 for 4.0l/manual, 3.54 for 4.0l/autos, and 4.09 for 2.5l/manuals).
NP207 - "Command-Trac" part-time only - 2.61:1 ratio low range - used 86-87
NP231 - "Command-Trac" part-time only - 2.72:1 ratio low range - shift pattern 2H - 4H - N - 4L - used 87-92
NP242 - "Selec-Trac" part-time OR full-time - 2.72:1 ratio low range - shift pattern 2wd - 4part-time - 4full-time - N - 4LO - used 87-92
The 207 was never officially used in 87, although I cannot say for certain that a couple didn't sneak though because they were left over and sitting on the rack. Weird things happened in the AMC-Chrysler transition years. I can find no evidence of the 242 ever being used in an MJ, but you missed the np-228 which was the Select-trac option (offered in 86 only) with a 2.6:1 low range.
Rear Driveshaft - The rear is a one-piece shaft with standard u-joints at both ends. The slip yoke is located on the output shaft of the transfer case. On 86-92 models, the yoke slides in and out of the transfer case and is lubricated by the ATF fluid internally.
Actually, there were 2 different styles of rear shaft offered, though I have yet to determine a logical pattern behind which MJ got which. The other one was a 2-piece design, but not the usual 2-piece you're thinking of where one side slips on the other. The MJ 2-piece had a large outer tube on the transmission side and a smaller tube on the axle side. They are fused together with a thick rubber isolator designed to reduce vibrations. It's kind of a funky design and hard to explain. All 3 of my MJs have/had it and I can snap a picture if you'd like.
Dana 30 high pinion - reverse cut - 27 spline, 1.16" diameter shafts, 7.13" ring gear - used 86-92 (some axles through 91 are vacuum disconnect, 89-92 with ABS have 5-297x u-joints, all others have 5-260x u-joints)
Except for the few 86 MJs that had the Select-trac 228 t-case (I don't know one way or the other with them) ALL MJs came with the Central Axle Disconnect (CAD). And NONE came with ABS or 297x joints. Those are XJ things.
Dana 35 non c-clip - 27 spline, 1.18" diameter shafts, 7.58" ring gear, 2.62" axle tube - used 86-89
Dana 44 non c-clip - 30 spline, 1.31" diameter shafts, 8.5" ring gear, 2.75" axle tube - used 87-89 on some(not all) MJs equipped with towing package.
(note for D44's: All MJ's equipped with the stock D44 come with the Metric Ton Package)
Add the AMC-20 (sometimes called the M-20). one piece axle shafts (unlike the CJ AMC-20) and I think it's a 8.875" Ring Gear and 29 Spline shaft. Metric Tonne axle in 86.
Oh, and the Dana 35 c-clip used 89+.
3.07 - used with 4.0L engine / manual transmission
3.55 - used with 4.0L engine / automatic transmission
3.73 - found in most MJs with the towing package
4.10 - used with 2.5L engine usually
4.56 - rare but can be found on some older (~ 89 ~) models with 2.5L engine and auto transmission
3.73 didn't come in MJs, but in 86 there was a "fuel saver" package where you could get a 3.31 ratio. (that package also came with the 2.5L, 4 speed manual transmission, and tailgate delete)
86 - Custom, X, XLS
87 - Base, Pioneer, Chief, Laredo, Sport
88 - Base, Pioneer, Chief, Laredo, Sport
89 - Base, Pioneer, Chief, Laredo, Sport
90 - Base, Pioneer, Chief, Laredo, Sport
91 - Base, Chief, Laredo, Sport
92 - Base, Chief, Laredo, Sport
Add the Eliminator to 88+ and the Sport was actually called the "SporTruck" and was the base shortbed. The "Base" was the base longbed. And the "Chief" was cancelled in 1990 I think, maybe 89. I know for sure it existed in 88 and didn't exist in 91.
I'm still missing dimensions.
Overall length was 179.3" for shortbeds, 194.0" for longbeds
Overall curb height was 63.7" for 2wds, 64.7" for 4wds
Track width was 57" with the 15x6 rims, 58" with the 15x8s
Body width at the rear flares was 71.7"
Length of inside of box at the floor was 73.7" sb and 88.5" lb
Width of box at the floor is 55.3" for both sb and lb
Width between wheel wells is 43.8"
Box depth is 16.4"
Any other dimensions you'd like?
Curb weight for the 2wd short bed was 2912
4wd sb was 3076
2wd lb was 2959
4wd lb was 3141
Payload for stock MJs is 1475 lbs (1200 for 86), Metric Tonne was 2205 lbs. The maximum tow rating an MJ was ever given was 5000 lbs (4.0L required). 2.5Ls seem to have been limited to 2000 lbs and 2.8Ls were 4200. I cannot find any rating listed for the stock bumper. Every brochure mentions a class 1,2,3 hitch needs to be installed for towing.
Hope this helps!