91 pickup having trouble going from 4x4 to 2x4
 

I have a 91 pickup that is being a devil when trying to go from 4x4 to 2x4. It shifts perfectly from 2x4 to 4x4 and goes from 4 hi and lo perfectly but for some reason when trying to put it back into four wheel drive it wont go. if I back up an pull ahead a couple times it will eventually slam back into 2WD but not nicely anyone know what this might be?

This might seen like a stupid question, but it isn't.

The 4wd is not to be used on paved roads because of too much traction. As a side effect, it often does not switch from 4wd to 2wd (and visa-versa at times). Did you try this while on a paved surface? If yes, try on a dirt lot or the next time you need it and if there's no issues, then what you described is completely normal.

I've been doing this in snow my 35's are terrible in 2WD and with Canadian winter I have to put it in 4WD a lot to get going if I'm in slippery areas but then she doesn't wanna go back in 2WD

Assuming you have the automatic hubs (ADD) then check your vacuum lines. They solely depend on the vacuum pressure to change. Then check the operation of the VSV's involved with the two vacuum lines... FOllow the FSM.

If manual. I got nothing :D

they're manual locking hubs

Same tire size front to back? Same tire pressures? Are you turning or going straight while trying to shift into 2wd? Are you on level ground or going uphill trying to disengage the 4wd?

You first said its hard to go from 4wd to 2wd, then say it's hard to put it back into four wheel drive. Which one is it?

my bad I meant to say going from 4WD to 2WD and its 35's all around 6" suspension all round

flat surfaces as well

Have you had the truck long? Just started shifting hard?

My '95 with ADD ( now hubs, but system not yet removed ) 22RE I have to slow way down to walking speed to get into 4HI, but once in 4HI I can ease back into 2HI in most conditions, I do clutch it though. This is with hubs locked of course.

Yes, check your vacucume lines, you have manual hubs but it still is an ifs using the VSV to shift the collar over to lock/unlock the axle. I have manual hubs as well, I shift back and forth quite a bit driving to work depending on the road conditions with no issues.

haven't had it long it was like that when I bought it and seems to be getting if anything thanks boys ill look into the vacuum lines situation see if it helps

getting worse***

Does it drive normally once it's in 4wd? Could also be different gear ratios front and back.

its alright in rough terrain but cant be driven at all on pavement it goes bannanas and its a solid possibility cause I know the previous owner changed gears in it to make it better for highway driving so theres a good chance he didn't match them

Ahh yes. Of course this makes sense. :)

That's it then. Find out what ratios you have front and back. You need to get the gears to match before it tears something up.

That is true if his truck was originally equipped with ADD, and the drive flanges were swapped out with locking hubs. But if his truck was originally equipped with locking hubs there isn't a shift collar in the axle housing, vacuum lines etc.

My truck was a 1990, a little older, but mine gave me problems too. What I did, and it worked everytime, is Ill go into 4hi, 1st gear, ease out the clutch and get my truck into a SLOW roll (going straight), once its moving, I press in the clutch, and put it into 2hi. It usually slips out of 4hi and right into 2hi pretty smooth.