96 Jimmy 4wd shift motor/shift module

I'm having a problem with my wife's 96 Jimmy. When you activate the 4wd system in 4lo (place shifter in N and push the button For 4lo) it engages no problem and all wheels turn (I had the truck on jack stands)when you shift into D,but when trying to shift into 4hi the buttons for 4hi and 4lo flash and then it just goes back to 2hi(it does this in N)When I push the button for 4hi while in Drive either moving or stopped nothing happens,the 2hi light just stays on ! Could this be the electronic shift module or the shift motor? I took the truck for a test drive and 4lo definitely works! I was wondering if there is some way to test the shift motor without removing it?I saw that to remove it requires dropping the front driveshaft.
I'm an aircraft mech. by trade and used to be a P.D.I. foreman at a GM dealer and I do all my own maintenance on our vehicles (my 87' 1/2 ton Scottsdale,my wife's 96 Jimmy and I am doing a frame off on my 69 K5 CST.) so I'm not mechanically inept !
Any info would be appreciated and if anyone ever needs any help with Boeing 737's I'd be more than happy to assist. :)
Thanks

Hey. I'm having a similar problem with my '98 Jimmy. The shift motor
can be removed on mine w/o removing the drive shaft but it is tight!!
The motor/gear case had a gob of RTV sealant inside that was interferring with the shift gear going to the 4Wlow position. I cleaned
it out and repaired a ground on one of the motor leads where it entered the gear case. Then you have to remove power to the controller to reset it-(I pulled the 50amp fuse under the hood.) It works fine now plugged in but unbolted to the case. At this point I think some damage was done to the transfer case meanwhile. (Shoot!) So tomorrow I'm going to remove it. (Once I removed the shift motor I was able to shift is with a wrench but it shifts real rough and it takes a lot of force too.) Good luch with yours. dp

I'm having a problem with my wife's 96 Jimmy. When you activate the 4wd system in 4lo (place shifter in N and push the button For 4lo) it engages no problem and all wheels turn (I had the truck on jack stands)when you shift into D,but when trying to shift into 4hi the buttons for 4hi and 4lo flash and then it just goes back to 2hi(it does this in N)When I push the button for 4hi while in Drive either moving or stopped nothing happens,the 2hi light just stays on ! Could this be the electronic shift module or the shift motor? I took the truck for a test drive and 4lo definitely works! I was wondering if there is some way to test the shift motor without removing it?I saw that to remove it requires dropping the front driveshaft.
I'm an aircraft mech. by trade and used to be a P.D.I. foreman at a GM dealer and I do all my own maintenance on our vehicles (my 87' 1/2 ton Scottsdale,my wife's 96 Jimmy and I am doing a frame off on my 69 K5 CST.) so I'm not mechanically inept !
Any info would be appreciated and if anyone ever needs any help with Boeing 737's I'd be more than happy to assist. :)
Thanks
I'm having the same problem with my 1997 Jimmy. Did you have any luck with your Jimmy yet?

I disconnected the battery for ten seconds. After reconnecting the problem was fixed. The actuator motor on the transfer case was locked up. If that doesn't fix the problem it's probably with the transfer case.

on the shaft where the shifter motor is installed there is a position sensor. when this is no longer working the only postions you will get is 4 lo and 2 hi because those positons are on either end and can no longer tell where the 4 hi position is. the only way to fix the problem is to buy the whole motor/gear/sensor assembly for about $300.00 or if your really lucky maybe the plug-in just came off or the wiring to the sensor has a break in it somewhere. good luck.