IFS front 4WD auto-engage mechanism

[SKIDPLATE]

Hey, has anyone had any experience with the clutch machanism in the front spindle assembly for the auto-engage 4WD ?

I was coasting off the mountain yesterday (slow, steep and rocky) in 4-low and started hearing a thunk, thunk, thunk in what sounded like the front right wheel assembly. It would thunk about every half revolution of the tire. I thought one of the kids was hitting their knee against the side at first. It drives fine on smooth flat roads. The only thing I could think of was maybe the pads that lock the front wheels when in 4WD might be wearing out. Any thoughts?

 

[n8buddy]

it doesn't sound like something that would come from the 4wd components. what year is the truck?engine?manual hubs or ADD? it only makes the sound in 4lo or does it make it in 4hi/2hi as well? im not sure about "the pads that lock the front wheels when in 4WD" ive never heard of that. more info please...

 

[ovrrdrive]

What shape are the CV's in?

The biggest problem with the ADD system is that the hubs are locked all the time and the CV's are always turning. The boots get brittle and rip open and then they CV's wear out from the sand coming in and grease going out. If your front diff is making a big thunk you have big problems.

 

[fourwd1]

it doesn't sound like something that would come from the 4wd components. what year is the truck?engine?manual hubs or ADD? it only makes the sound in 4lo or does it make it in 4hi/2hi as well? im not sure about "the pads that lock the front wheels when in 4WD" ive never heard of that. more info please...

You are correct, whether you have manual hubs, auto hubs, or ADD, there are no pads involved in engaging the 4WD system.

More info would definetly be helpful.

 

[SKIDPLATE]

We'll see if this fixes it.

A buddy of mine, after listening politely to the problem and all of my ideas for a solution, brought up something that I believe none of us thought of. He suggested that the problem might be with my motor mounts. The other week the shop that replaced my ball joints had even mentioned my mounts being a bit less than firm. I order a set for under $100. Even if that doesn't fix it. they need to be done anyway. Are we taking any bets?

 

[SKIDPLATE]

Oh, yeah.

The CV's all look great. All the bushings look good. It does not have ADD. My understanding is that the ADD option was available in 4r's later than my 89. Stands for Automatic Drive Disengage or something like that. It's a settup that disengages the left drive shaft from the Diff in certain conditions. My impression is that no one who seriously uses their 4WD likes it at all. Mine, however, have Auto hubs... not the same as ADD. From my Toyota manual it shows that there IS something almost like a drum brake pad inside the hub assembly that does the actual locking of the hub. I don't know how it works though.