My 1999 JGC started going into limp mode last winter with a P0700 code. Auto Zone helped me pull the P1781 code from the computer and after all my research this was my solution. If I shut my car off after a few miles and restarted it would work fine. I researched a ton, thinking it could be the TCM, the battery terminals, or the speed sensors. Turned out to be a bad solenoid pack in the transmission. Here are all the links and info I found in my extensive research. Turns out this wasn't all that uncommon a problem. But I couldn't find a video!
It's been 6 months since my DIY fix and no problems! Shop wanted $700 plus the price of the part. I spent $200 on a refurbished solenoid pack and another $50 for the filters and trans fluid. Took half of a Saturday and saved me hundreds, and I'm no mechanic. Here's a copy and paste of all my research & links. Good luck!
Transmission Manuals:
https://dl.dropboxusercontent.com/u/78762721/45RFE.pdf
https://dl.dropboxusercontent.com/u/78762721/2004%2057%20hemi%20trans.pdf
**pages 452-463 on this document helped the most!**
Code P0700 *Transmission control system malfunction indicator lamp request
Solenoid pack
Part #68002342AD
- sold at Brent Brown
Older part numbers: 4799934AB
934AC
934AD
P1781-OD PRESSURE SWITCH SENSE CIRCUIT One of the Pressure Switches in transmission is closed at the wrong time in a given gear.
POSSIBLE CAUSES:
TRANSMISSION RELAY DTCS PRESENT
INTERMITTENT WIRING AND CONNECTORS
TRANSMISSION RELAY OUTPUT CIRCUIT OPEN
O/D PRESSURE SWITCH SENSE CIRCUIT OPEN
O/D PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND
O/D PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE
O/D PRESSURE SWITCH INOPERATIVE
TCM - O/D PRESSURE SWITCH
CHANGING OUT SOLENOID PACK
http://www.jeepsunlimited.com/forums/showthread.php?t=506182
REPLACING TRANS FLUID
Need: cooler return filter (optional but recommended)
Filter
Gasket and/or RTF
ATF+4 trans fluid (5 quarts)
Undo 10 bolts. coat with RTV silicone to make a gasket don't add fluid to a cold trans (except for initial add?)
http://voices.yahoo.com/how-change-transmission-fluid-filter-in-5780722.html
http://www.jeepforum.com/forum/f197/grand-cherokee-crd-transmission-fluid-change-1394418/
http://www.jeepforum.com/forum/f13/45rfe-questions-568844/
45RFE TRANS INFO
http://www.atraonline.com/gears/2001/2001-03/24_dr_dr.html 
