I have 31x10.5x15 tires on the rear and stock 15in tires on the front of a 96 Jeep Grand Cherokee. The front end is trying to lock in 4 wheel low. Is it because of the different size tires? Can I disable the speed sensor on the front end?

Your front end is engaged with a vacuum line . make sure the line is good. You will find it comeing off front axle.

A 96 Grand Cherokee rear end is not compatible with the 99. The Grand Cherokee changed body styles in 99, and among other things, the bolt pattern for the wheels changed.

I hava a 1999 Grand cherokee loredo V8 with full time 4wheel drive. when the rear tires slip I am hearing a poping noise in the front end when the 4wheel drive engages. I was told by one person that it could be the chain in the transfer case slipping but I was told by a jeep salesman that this year jeep did not have a chain. Could this be the CV joints in the front axels?

Get some adjustable coil spacers.

If you have a CJ or Cherokee, when you move the 4x4 lever, it engages the transfer case which then transmits power to the front as well as the rear wheels. For most (99%) of all four wheel use, you use the front position on the shifter one notch behind the two wheel drive setting. Use 4 low only for pulling vehicles out of mud etc and don't drive in that range. If it sticks in 4wd after disengaging it, usually backing up about twenty feet will help.
If you have a Grand Cherokee, the 4x4 usually is a quadratrack unit. That one stays engaged but only goes into 4wd mode when the rear wheels begin to slip. (by itself). Rules for using low are the same.
It is very important to run the exact same size and style tires on any 4x4. It is mandatory on quadratrack units. Use of odd sized tires can cause driveline damage.
There are variations on different year vehicles but the basics remain the same.

Move the passenger side rear tire to the front, and passenger side front to driver side rear. Switch the driver side rear tire to the front and driver side front to passenger side rear. Repeat this "X" pattern each time you rotate the tires. Rotate the tires from side to side if the tires are different sizes on the front and rear.

This is the better solution. Hope helped (remember rated this help)

For more details about Jeep Cherokee, review the Service Manual.

Good luck.

You cannot drive with different size tires front and back, especially with full time 4x4's the tires travel different distances when rolling.. a one inch height difference translates to a three inch rolling difference...ten turns of the tire = a thirty inch difference in distance traveled between the front and rear of the vehicle..being all attached to the same point (the transfer case) there is no way to compensate, therefore something must fail or the vehicle will stop in a locked up (bound up) condition. The weak link is the viscous coupler in the transfer case...likely what has failed.

the tires & rims that come with your vehicle are designed to meet all the specs of your vehicle. When you change sizes and styles, you then need to get the computer re programmed with the tire changes you have made. It affects your speedometer, your transfer case, your fuel (mpg) and the performance of the engine to the wheals. Also you can damage your transmission and rear end. So my advise is to buy a high end tire that meets origional specs. Look at the Toyo's they are great tires, great performance and no alterations are needed. Pluss they look cool as hell so try that
http://www.treadepot.com/
check this site out and call them, they have better deals on the phone and have fricking great prices on tires.

Let me know how it goes.

tepfy

if it is a roaring noise it is probably a wheel bearing going bad

usualy you will only have two tires spin at a time even in 4 lo or 4high. those tires are going to be diaginal from each other tipicly. now since your vehcle is equiped with quad drive it may employ a limited slip rear differential to help it along. however this only afects the rear axle. now you can test it by jacking your vehicle up and setting it on jack stands. one for each wheel onder the axle tube on a good solid (concreat or black top) flat surface. then have some one you know and trust to get in the car and put it into drive . now you can actualy see what wheels are spinning or not.now is were the limited slip comes in if you have one rear wheel spinning and the other is sitting still the limited slip will engage and start the other wheel spinning . now this may bang until the other wheel catches up (note that the faster the wheel is spinning the harder it is on your truck)now be very carfull stay away from the wheels tires and all other spinning parts it is a machine it can hurt you badly. but give it a try and it will answer your question. be safe hope this helps