Purchased a used Jeep Commander 7 passenger, 88,500, 3.7 v6, 4x4 sport last month. Since I have no lever to engage the 4x4, how does it work? I don't know if I have a QT I, II, or III. Does the car have a timing chain or belt?
You have QT-I which full-time 4WD; you have the NV140 transfer case, which is a single speed transfer case, meaning you do not have the capability of dropping down into 4-LOW; You're in 4-HIGH all the time.
Conversely, you don't have the ability to come out of 4-HIGH ever - meaning you don't have the ability to switch between 2WD or 4WD either.
Here is everything you need to know about identifying your Commander's 4WD system;
This Picture is a good indicator of what 4WD system you have:
If you have a Commander that says 4x4 on the rear hatch door and you don't have a chrome T-Handle like the one circled in blue, you have the Quadra-Trac I full time 4WD system.
Keep in mind, all three of the Commanders 4WD systems also come with the additional features of 4 wheel traction control and electronic stability control, so even the Quadra-Trac I 4WD system is quite capable when off-roading or trail riding.
If you do have the Chrome T-Handle but you don't have the Quadra-Drive II Badge circled in red then you have the Quadra-Trac II 4WD system.
If you have the Chrome T-Handle and the Quadra-Drive II Badge, obviously you have the Quadra-Drive II 4WD System.
Other ways to tell is by looking at the rear differential cover; Quadra-Drive II will have 12 bolts; Quadra-Trac I & II will only have 10 bolts. Here is a pic of my rear differential cover - I have Quadra-Trac II and as you can see there are only 10 bolts (2 hidden by a cross member)
The biggest differences between Quadra-Trac I and Quadra-Trac II;
Quadra-Trac I Commanders use the NV140
transfer case which is a 1 speed transfer case and not 4-LOW capable.
Quadra-Trac II and Quadra-Drive II 4WD systems both use the NV245
transfer case which is a 2 speed transfer case that is capable of dropping down into 4-LOW.
Quadra-Drive II offers the additional capability of ELSDs (Electronic Limited Slip Differentials).
To answer your other question - I'm pretty sure you have a timing chain, not a timing belt.