4 wheel drive engaging 'slow'..is it the vacuum hubs?

[92 5 oh]

Hello,
I'm new to these pulse vacuum hubs on my 98 4L ranger. I've noticed that after i put the truck in 4H or 4L it doesn't immediately engage, sometimes when i start driving it will 'clunk' and engage. I noticed that after i put it in 4 wheel drive the motor on the transfer case seems to engage quickly - like 2 seconds or so and doesn't appear to have any trouble disengaging either. So it didnt sound like it was in the transfer case motor, i was thinking it might be in the hubs. I was thinking about locking the hubs like it says on the tech page but are there any downsides to doing this?

thanks
steve

 

[92 5 oh]

anyone?

 

[mhughes165]

do u go in reverse like ur always supposed to when u lock a vehicle in 4wd?? when u lock a vehcile in 4wd u need to back up slightly which gives any hubs a chance to lock properly, isntead of a delayed lockin like you experience going forward

 

[dogboy]

I always thought you back up to unlock them, not lock them...

Why would they say you can shift it to 4wd at highway speeds if you have to put it in reverse?

 

[4x4RangerGuy]

Unless you have a vacuum gauge, the best way to check if your hubs are working are to take them off.

There are a couple usual suspects in the vacuum system. The oring likes to shrivel up and leak, the seal that is pressed into the back of the steering knuckle gets chewed up and likes to leak, and occasionally the vacuum lines like to leak.

 

[gotmudd]

I always thought you back up to unlock them, not lock them...

Why would they say you can shift it to 4wd at highway speeds if you have to put it in reverse?

WHY would you want to shift into 4wheel drive at highway speed? and my next question is "who are they"? driving in 4wheel mode is not a good idea at highway speed unless it's on snow pack or ice. as for putting it into reverse, that is to take the strain off of the drivetrain. i would listen to 4x4RangerGuy and use a vacuum gauge and check your o-rings and vacuum lines

 

[TRX501RYAN]

Ive switched into 4x4 at highway speeds, only in the winter when i hit bad stretchs of road.

 

[Jspafford]

What's wrong with using 4WD on the highway.

I certanly don't come to a stop to shift into 4WD in the snow. Let off the gas, flip the switch (f-250) or pull the lever (B2) and keep on going.

The only drawback to permanantly locking the hubs is there is going to be a little more drag, so you may lose a MPG or so.

 

[92 5 oh]

man i forgot all about this thread. i'm going to attribute the issue to a poor seal or maybe a vacuum leak. now that it's warmer it seems to engage as normal, i'm guessing because the seals aren't as hard or shrunk?. i'm going to pull the wheels and check the seals, i'm also occasionally hearing a 'squeeking' that seems to be worse (or starts) when 4wheel is engage. then as wheel speed increases the 'squeek' increase, so its related to wheel speed. I think this is the seal on the back of the wheel/hub assembly. after researching it, i found a few others who have had a problem with 98-99's doing that. so we'll see what happens