4wd kicks out @ 45 MPH posted on Rodeo also

[foxtiger]

Bought a good used 98 Amigo 62,000 miles. Winter is approaching and I thought I would try out the 4wd (push button). Rainy afternoon.
-Punched the button around 30 mph.
-Indicator light comes on
-System goes into 4wd
-Slight wine but not bad.
-Everything is fine until the vehicle reaches about 45/50 mph.
-Every shifter goes into neutral !!
-Transfer shifter jumps to between 4wd hi and 4wd low.
-Clutch seems to dis-engage but I know that is because the transfer case went neutral.
-Have to pull over and stop to shift everything back to it's rightful place.
-Turn off the 4wd (push button) and go on my merry way.

This happends every time. It is fine if I do not exceed 40 mph.
Is there a limit set that can be adjusted or am I looking at a big ticket repair?
I did check the size P245 70R 16. The size and manufacturer Michelin are the same but the rears are different from the fronts in that they are different models (Cross Terrain SUV) on the front (XCX/APT) on the rear. I will go on the net and check the specifications of the type tire. They are 29.5” diameter for the Cross Terrains and 29.6” diameter for the XCX/APT. There isn’t a big difference between the two but at 45 mph the revolutions are different by 2 RPM (fronts are turning 709 RPM and the rears are turning 707 RPM). Another factor would be how long were these tires on the vehicle and is one set worn more than the other. Is this difference that touchy when it comes to 4wd?
Thanks Larry

Thanks