Does anyone know what the cruise control looks at to know what speed it is going?
I'm trying to get mine down to 25-30 mph from 40 mph.

The speed sensor on the trans. Can you explain what you mean when you say you are trying to get it down to 25-35? Is it not operating at the lower speeds?

I think he means lower the minimum speed for the cruise to engage.

Yes the lowest speed I can achieve that cruise control will hold is 37 miles an hour I would like for it to be between 25 and 30

If it's possible I'd certainly want to but I doubt it is. The cruise control system is controlled by the PCM.

You will need to find someone that can reprogram your PCM, the only way you can change it. Your best option is the stealership

I believe that it's possible to modify the cruise control system to work as a high idle device but not sure if that will work to do what you want to do. Do a google search for "Jeep XJ Cruise Control High Idle".

The FSM for my 97 states that the speed control is designed to operate between 35 and 85 mph. The FSM is a bit wordy, but basically, the Vehicle Speed Sensor (VSS) pulse signal is monitored by the PCM to determine vehicle speed and maintain speed control set speed.

Yep, very few vehicles will operate cruise that low. I have read that it is for safety reasons. I have one (a Toyota), and it's the only vehicle I have ever driven that will allow the speed to be set that low. I have heard of some others, but they are a distinct minority

Since it's considered safety issue, the dealership is NOT going to change it for you. Think about the liability if they modify your computer's safety limits and you run over a child in a residential area while on cruise control and not paying attention.

Fuggedaboutit.

My 2011 GMC Sierra 2500HD has it's lowest cruise speed at 25 mph.

All of mine were between 35 and 40...Don't think it will engage below 35