Here is what I have always figured happened, while there are facts in here, a lot is my assumptions....so take it as you will
Cj- Civilian Jeep (duh) 1941-1986 2a-10
Xj- 1983-2001
The X was Engineering code and project code, as this was the first of its kind, a cross over (ie X) between a station wagon and a true 4wheel drive. A kind of utility vehicle for sporting people who liked to do things outdoors.... like a sports utility vehicle (SUV).
Side fun fact: The concept for the Xj was actually supposed to be an eagle wagon thing, but when Renault took controlling interest of AMC in 79, they moved the project over to jeep, as the fsj's didn't sell in Europe because they were literally wider then most medieval streets.
now who remembers there alphabet what comes after X....
Yj- 1986-1995
Zj-1993-1998
And Sh*t We ran outta letters, Lets go back to J and start again
Wait! you the one whos about to yell about the Mj (1986-1992), yes the mj came out in 86, before the Zj, but the Zj had been in development since 83 with the xj and yj, therefore their engineering codes came first, so...be quiet.
at this point jeep said whoops, lets not let that happen again, went back a few letters and ear marked K,L, and M for new Cherokee models, like the Comanche(Mj). They ear marked T,U, and V for future Wranglers. N,O,P And Q,R,S were assumedly kept open for new models, or projects we never saw
and here we are
Tj-1996-2006 (yes 96, I will fight you on this!)
This is where things get weird
Wj-1999-2004
my best bet on what happened here has to do with the Daimler-Chrysler merger in 1998, specifically (1998-2007)
or as I like to call it, the dark times. the Zj was supposed to be the successor to the Xj and eventually replace it all togeather like the Grand Wagoneer replaced the Wagoneer and Cherokee chief before it, but no one expected that thing to sell well effectively unchanged for GD 14 MODEL YEARS! Thus we get the Wj, because the Cherokee will need those letters we ear marked for.......sh*t
Kj- 2002-2007 yup... this was a good idea, Xj people will be so happy we got rid of that dumb solid axle and legendary motor, and replaced it with this. They liked it so much that the Kj carries the Cherokee name everywhere BUT north America, thanks Daimler
And where back to where we started, outta numbers, outta letters(ish?), What should we do now? I know we will go back to where we were before, and go to the next letter after j....k. why do we even need that stupid j anyways! thanks Daimler
Wk- 2005-2010
Xk- 2006 -2010
so help me god, If even one of you brings up the mk74 on the gs platform and say I forgot a "Jeep".... I will meet you out in the parking lot.... try me
Jk- 2007-2018
Hey look a new pattern, Somebody done figured out that J might mean something!
not gunna bother with kk,wk2,Kl,or Bu, I don't feel I need to explain why....
Jl-2018 to present
Jt- 2019 to present
it would appear that only wrangler derivates will carry the J moniker any more, but incase it not blatantly obvious by now, who the F know what jeeps going to do next. however, I do feel with the Jl and the Jt, Jeep may be making its way out of the dark times.