Odd shifting 99 jeep grand cherokee

You need to have the transmission control module tested for fault codes, AAMCO does this testing for free.

Try adjusting the transmission cable that comes from the throttle body. That is where the transmission gets it's input for how much throttle is being requested. If it's misadjusted and thinks you're requesting too little throttle, it may try to downshift more than normal. It's been a while since I've done this on mine so I don't remember if this is the exact procedure or if there are additional steps, but you have to pop the clip for the throttle to transmission cable and slide the cable as far in as possible then put the clip back. Next you'll want to press the gas pedal all the way down (may have to use extra force). You'll hear a pop and you're done. If you mark beforehand, you can see if adjusting did anything.

Cruising rpm even after the OD has engaged has a lot to do with the differential gear ratio and tire size.
There will always be a variation between different vehichles due to that alone.
To see if the OD is working, at about 50mph, lightly touch the brake pedal. If the rpms increase for a moment then the OD was engaged. (touching the pedal momentarily disengages it...good thing to know when hill climbing!

My jeep does the same thing but from 1st to 2nd i was told the solenoid valve in my valve body sticks until the fluid is warmed up and opens up.Cheapest thing to do is let your jeep warm up for a little bit to let the fluid cycle.

Dirty transmission filter.
Most "service" places only pump out the fluid through the dipstick tube and tell you that the filter will be OK. That way they don't get an ATF bath when they pull the pan.
I'm guessing that the crud in your tranny is pluging the filter after a few miles, when you shut it off, the fluid runs back down, washing the dirt and metal pieces back into the pan.

change the Speed sensor on the transmition.  On my 99 it would not shift out of first gera when my gas light would turn on. Every time it happened untill i filled it up . I changer the speed sensor  and all is fine

transmission?

Well, in the future it would be better to let us know what it is exactly that you drive, (cherokee, grand, jk, cj, ....)however, i'm guessing from the picture that you drive a grand. I dont know how long you have owned it or if you have put it in 4 low before, but you need to put the normal transmission in neutral before shifting to 4 low using the transfer case (the thing that gives you 4wheel drive via the lever) However, on your vehicle, if you have full time 4 wheel, i think you have the selec-trac transfer case and only have a switch. According to the Jeep website and i'm assuming your manual, you need to slow the vehicle to 2-3 miles per hour and then place it in neutral before attempting to shift to 4 low.

Jeep Site
http://www.jeep.com/en/4x4/how_systems_work/selec_trac_2/

Joel

Calvin...... You need to treat your Jeep to a new THERMOSTAT. The Overdrive is connected to the engine coolant temperature and if the engine is n ot warmed up properly, the Overdrive will not engage. Try to get a thermostat from the Jeep dealer so you will have exactly the right one, some of the cheapoie ones will not work right. Dave in Iowa