Stick shift.
There are several things that can cause your 2005 Jeep manual transmission to shift hard between first and second gear. The most common cause is a malfunctioning shifting fork.
If a 2000 Jeep Wrangler suddenly loses power in 5th gear, it might be a problem with the speed sensor on the transmission. This sensor regulates when the Jeep will shift or should shift.
Worn synchonizer?
your shift lever bushings are bad, easy fix.
Your synchro is going bad.
Stick shift, yes. Automatic, no.
75w90 gear oil75w90 gear oil
If it will shift when the engine is off, but not while it is running your clutch is not working
Look at the gear stick, if its auto then you have an auto transmission, if its manual you have a manual transmission.
sell jeep and just buy the manual one
it is probably your shift lever bushings, but check the rubber seals and carpeting, sometimes they put pressure against the shifter making it pop out of gear.