I have a '93 Rodeo, When i take it out of 4X4, It goes out fine, when i get upto 30mph, the left front auto hub starts grinding, as i slow to a stop, i get a couple good clunks, and then it seems released until i get back up to 30mpg, then it starts grinding again.
I took the hub off and degreesed and relubed the hub and it still does it. After i park it for a few minutes, its fine to drive in 2WD again.
Any ideas what i should look for, It almost seems like a valve isn't relieving the Vacume pressure, to release the hub. Or whatever makes it work.
Thanks in advance.

If it was me, and if it was possible, I would switch over to manual hubs. Manual hubs would 'unlock' the front end and save wear and tear on the front end components. Look for a good set of Aisn hubs.
Jim

I was looking at a set made by superwinch, but they list them for the Trooper, Are they the same hub styles?

As long as they were for an 88+ Trooper, yes. All Isuzus from that time forward use the same front differential. There were some changes in the latest (2002+) years that affect one's ability to bolt on a set of manual hubs; but that doesn't matter in your case.

will this work on a 97 passport that will not engage the 4wd? i have to reverse the vacuum on the diaghram on the front axle to engage mine.

My experience is with a 99 Rodeo but if it's the same then the hubs are not automatic or manual. The hubs are permanently connected, what allows 2WD/4WD is a vacuum operated clutch on the LH axle, inboard of the hub. This might sounds strange but by disconnecting one axle the front diff does not allow any drive effort to the front wheels. Re-lubing the hub itself will not tell you anything.

Is it possible your vaccum clutch is staying engaged but you only hear it above 30mph? Is your steering more difficult than usual at low speeds?

Seems like you need to check out the vacuum clutch.

thats sounds like it could be true to the problems im having, all the noise (grinding) is always in the left front wheel. i know when i had the hub off, i could see the gear force out in 4wd. but when i would put it back into 2wd it was real sluggish to retract the gear. What do i gotta look for as far as what ingages, and disingages the gear for that left side? hopefully you guys can save me alot of poking and hoping,and lead me in the right direction, as far as where to look.

What do your front hubs look like? Do they have a dial in the middle or AUTO on the outside cover?

I don't think you have the hub style they used in the newer Isuzus. If you are seeing a "gear" of any kind in the hub, then you do not have the style described above.

Do you have something mounted on the axle tube between the differential and the driver's side hub? Do you have a button on your dash for 4x4, or just a lever on the floor?

Michael

Yes, if you can see movement in the hub when you engage 4WD then this is not the arrangement I am familiar with. My apologies.

'99

Just a shifter on the floor, The hubs are Auto, with a 6 bolt pattern, When i was referring to the gear, it can only been seen when i remove the hub.(6 bolts) and there is a spring loaded gear behind it, on a splined shaft, (axle shaft) That when the 4x4 is ingaged, it pushes the gear into the ring gear in the outer hub. and the spring should push it back when out of 4x4, but something is keeping it from going back.