Hello everyone.

I have a 2003 f150 4.6 automatic super cab short box with MSOF 167k on the clock. It seems when I put the truck in 4 hi everything is fine the shifter feels as it should an the dash light illuminates instantly. When I put the pickup in neutral and put my foot on the brake to put the pickup in 4lo it grinds then my speedo goes all the way to 100 mph then back to zero then no more grinding accrues. I then put the transmission into drive and I can feel it because the pickup has a harder lurch into forward or reverse. However I tested this on a hill in 4hi and 4 lo as soon as I let up off the brake and apply my foot on the accelerator it jumps out of 4hi and 4lo. Any ideas would be greatly appreciated on this. I live in northern Minnesota and it would be very handy to have the 4x4 working tip top before the snowy months start