urgent 91 4x4 problem

[ezmonie4]

ok so i have read the things about 4x4 shift motor with no luck so here is my problem. My try will shift into and out of 4 wheel hi no problem. so i pulled motor out hopeing it was the little stop every body has problems with but it looked to all be pretty new so put it back together. so pluged it in under truck while son pressed buttons and motor shift to hi but when low is pressed motor trys to turn shakes and then shifts back to 2 hi. have tryed everything i can find on here and no fix. Could it just be bad motor???

 

[Anime]

The problem might not be the shift motor, but the control module (located on the drivers side in the rear behind the body panel). Sometimes the capacitors leak and cause big problems with the circuit board, screwing up the 4WD operation.

The switch can also go bad just from use or age, sometimes you can pull it and clean the connections and get better operation.

I've also found that even with these problems, if you drive a little in 4WD HI, sometimes it'll switch into low range the next time you stop and push the switch, or it might just take a few tries.

 

[MrShorty]

motor shift to hi but when low is pressed motor trys to turn shakes and then shifts back to 2 hi.

Remember that the Hi-Low shift is not synchronized on these. It is not uncommon for part time 4wd system to have some trouble shifting between hi and lo. In addition to anime's suggestion, I might also suggest that you try shifting while the truck is rolling slowly.

 

[Anime]

It won't shift into low range with the vehicle moving at all. It has to be completely stopped for low range to be engaged. Engaging low range while in motion, even if it worked, would damage the transfer case in short order.

 

[MrShorty]

I think a lot depends on how you approach it. I have shifted all of my transfer cases into lo at very low speeds. Electric shifts usually have some kind of "fail safe" that prevents the shift computer from shifting while moving too quickly, but all of them allow for some motion (less than 3 or 5 mph or so). They also require you to be in N.

I will often bring the truck to a near stop, shift transmission into N as I approach the stop and shift into L as the truck is coming to stop. I often find that allowing the truck some motion makes for a smoother shift (gears can mesh smoother with a little motion) than coming to a dead stop.

 

[siguaw]

Mine only shift into low at a complete stop and must have foot on the clutch and the brake. Even if I am at a dead stop it will not shift until brake is held down. Not sure if that helps or not