How can I tell if I have the rear diff with TT or without?

By TT you mean TrueTrac? By Detroit/Eaton? If so, it is not likely you have one as they were never standard equipment in the KJ. Do you mean Trak-Loc? Start by calling a dealer and getting a copy of your build sheet. They are not always 100% accurate, but that should tell you pretty definitively what is in the rear differential.

_________________
2006 Limited CRD: Frankenlift II, Fumoto Drain Plug, DIY Stage 1 Tune, In-Tank Lift Pump

If TT implies some sort of limited slip then it was an option on the 05s, check build sheet, and it was not available on the 06 as it's incompatible with the stability control system.

_________________
Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

Thanks for all the information.

Go to this web page, under "YOUR VEHICLE" on the left click on "Equipment Listing", then plug in your VIN number.
https://www.jeep.com/webselfservice/jee ... %2527%2529
It will provide you with a factory build sheet for your vehicle.
If it came with a Trac-Loc rear differential, this will tell you.

Now if someone changed it later on, you will have to jack up one of the rear tires until it is off the ground, (block front tires for safety) then place transmission in Neutral emergency brake OFF.
Then try and turn the jacked up tire by hand; if you are able to spin it freely, it is an open differential (not a limited slip). If you cannot spin it by hand, it is a Trac-Loc.

_________________
Supporting Vendor and Moderator of LOST
05 Jeep Liberty CRD Limited
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
IronrockArms/wwdieselMount
98 Dodge Cummins 24 Valve