1990 wrangler yj tachometer doesnt work

SOURCE: 4wd problem jeep wrangler yj 1995

i just bought a used 97 CHEROKEE but i had the same problem, when i got to looking at it i found out the front driveshaft was shot, look at that, if its not it i would say its probably the transfer case especially with an older vehicle like that which is a very expenxive repair

SOURCE: missing factory throttle linkages on 1990 YJ jeep. Need Diagram

Go to any scrapyard and you can get the entire setup for next to nothing...and you can see how it's hooked up!!!

SOURCE: 4 wheel drive doesnt work.

Has this Jeep been modified at all?
It sounds like the shifter cable was reinstalled backwards.
Specifically the 4-Low "Not Climbing Well". 4-Low should give you the best torque and hill climbing ability.
Do you feel any "Binding" in the steering wheel (difficult to turn)?
Remember a Jeep uses real driveshafts and differentials to give you 4WD - you cannot engage 4WD or 4-Low on dry hard surfaces. It needs a little bit of slip between the wheels for turns.
Check you're fluids too.

SOURCE: wipers not working properly

Buy a Haines manual...$15 bucks at most parts stores...

SOURCE: caster adjustment for 1990 jeep yj wrangler

caster is adjusted at the rear of the lower control arms. Camber is fixed and cannot be adjusted by normal means (though special off-set ball joints are available to do that) Toe in is adjusted by turning the sleeves in or out on the tie rod ends. None of this should be done at home though crude adjustments can be made in order to get the front end reasonably straight. Adjustments are made on an alignment machine that allows precise adjustments to all you mentioned as well as front/rear tracking.