Auto trans wont hold first gear in 4low or 4high

[90xjblue]

Hi guys, I got a buddy with a 1991 cherokee 4.0L HO with auto trans and 3.55 gears. While going down hill his transmission seems to not want to hold first gear like my cherokee or any of his other 3 cherokees. When going down hill in first it just randomly shifts into second and catches you off gaurd, can be scary at times. I have used the search and cant find anything on it.

all of our cherokees are autos and they all hold first gear in 4 low wayyy better than the 1991 jeep, any ideas?

 

[90xjblue]

bump

 

[MT Mike]

Unless you have an aftermarket controller such as this one or a complete shifter such as these you're not going to be able to easily control the 1-2 shifting in your Jeep.