Shifts sporadically when driving - 2000 Jeep Grand Cherokee

check the VSS sensor as it controls both areas of your problem

Why are you not taking a 2014 car back to the dealer under warranty?

I\'m only 4yrs into the Audi Family but I recall experiencing a very similar problem in my first year of my new 2010-S4.
My Problem:
My JERKING consistently occurred while I was coming to stops, applying my brakes, the transmission was dramatically downshifting.
Audi\'s Response:
Transmission needed to finish learning my driving style which should happen within the first 500 miles driven. I wasn\'t a fan of that solution and started to analyze the problem.

Kutty\'s Conclusion and Results:
Speed up the learning Session with my Triptronic Shifter - I would drive the heck out of my S4, not as an adiot risking damage to to the vehicle. But, I was on the thought process of not having restrictions and being VERY AGGRESSIVE - FORCING EXTREME UP&DOWN SHIFTS

possible that there is an issue with the torque converter clutch servo/solenoid operation
take it to an accredited service center and have it properly diagnosed

For car not changing gears it can be shifter assembly issue, or it can also be transmission issue. Get the shifter assembly inspected with ignition OFF.

For more troubleshooting, I suggest you to get the Following help link checked, its complete step by step procedure to inspect gear shift issues: -----

GEAR SHIFT ISSUES

http://alltypesofpartsreplacing.blogspot.com/2012/11/gear-shift-issues.html

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These will help.

Thanks.

This is classic limp in mode. The computer won't let it shift to prevent further damage to the transmission. Gas mileage will go down because you're stuck in low gear. P0700 is a pretty general code. You need to get it to a shop for a diagnosis

if you have specific details as to the times , rpms , conditions that cause the problems take it to an accredited auto transmission specialist shop and have it diagnosed
with your details they should be able to pinpoint the fault as it will not be uncommon

you said you have to drive it everyday to keep it charged right? sounds like the alternator works. if you let it sit it goes dead? you might have a draw(somthing draining battery). or possibly a bad battery!

Check wire to transmission it sounds like a ground out when you hit a bump ,

Most likely the turning on and off might have trigered or burned out your relay switch located in the front of your engine. The overdrive button on your nissan was only ment to be used sporadically and not as a stick vehicle ( According to your expression ). You can purchase this relay in your nearest nissan dealer. Good luck.