So last week I took a trip to Mammoth Lakes, CA from Orange County, CA , around 700 miles round trip, and had a few questions and a small (I hope) problem with the auto locking hubs. Just before the trip I noticed at idle and up to around 2,000 rpm with no load (neutral and parked) the engine had a little "stumble". Not major, and no noise from the inards, but if I upped the revs with my hand at the throttle body, when it hit that "stumble", the engine visibly rocked a bit. Inside the rpm dropped maybe 250 and picked right back up. Spaced about 3-4 seconds apart depending on rpm. I first noticed this because one day the stock oil pressure gauge was bouncing around at idle, not by much, but quickly, and I at first chocked this up to electrical. I also noticed this (only once) at cruise on the way up, 65 mph, 2,800 rpm, and around 35 psi indicated (warm). Of note, I just switched to High Mileage semi-syn oil and have been adding about a 1/5 bottle of Sea Foam to the gas (89 octane) at fill ups. No stupid lights came on the whole trip. Any ideas? The other thing seems to be a slight harmonic vibration between 50-65 mph. Vibrates the inside mirror a little but isn't present at other speeds, and only in 4th when accelerating and 5th at cruise. Thinking older tires need replacing. Now for the 4X4 part. I was stuck behind a garbage truck on an icy turn on a small narrow hill, the idiot was stopped and was trying to wave the cars around him, hence we were all stuck on the icy hill behind him. Being stopped in neutral, I put it into 4-Hi and eased the clutch out. The rears broke loose and in about a second the front hubs locked with a tremendous "grab" is the only way I can think of it, and pulled me up and around him. I got to a flat level spot at the hotel, put it back in 2-Hi and backed 10 yards or so, pulled forward and it felt as though the hubs were unlocked, so I parked for the night. The next day, backing out of my spot (wheel turned almost all the way to the right) it felt like the brakes were on the right front wheel. So I put it in 4-Hi (with the steering wheel straight) till the hubs locked (backing this time), then drove the length of the lot forward, about 30 yards, and then in 2-Hi I backed up 30-40 feet or so (again steering straight). Started driving and when I turned hard left to get out of the hotel parking lot I felt and heard a pop and from the right front (as well as the braking feeling). Inspected it and nothing was broken (visibly) so I started to drive and I could feel the pull to the right (I assume the hub was still locked on that side). Another attempt and it "unlocked". The only other time I had to put in 4-Hi that trip I moved the lever to 4-Hi and backed 30 feet, then drove forward for about 1/2 mile, noting that in the very slight turns the inside wheel would grab (more so than any other 4X4 I've ever drove. Also when unlocking it took 2 attempts to get the transfer case to engage 2-Hi so I could back up and 2 attempts backing at least 40 feet to get the hubs to unlock. The outer boots are cracked and look like they've been that way for a while. I'm thinking the joints are bone dry and shot, but I noticed a grease nipple on the joint and was thinking I may be able to just grease it up and reboot it. Is there an easy way to tell if they are shot. Any help would be appreciated. Thanks in advance.
Thanks

Years and years ago the very first mod I made on my '91 Trooper was to get rid of the auto hubs. I have never known anyone who was happy with them. They were unreliable and unpredictable. I am totally surprised that yours were still working after all these years.

So do you still want my opinion of auto hubs?

I have considered the switch to manual hubs, but for now I don't have the time to make the switch. That was the first time I needed to lock them up (other than once a month to "exercise" the drive train). If I have to replace the CV joints, then I may go that route, but most likely rebuild the auto lockers. Honestly, I'm just putting into it what I need to, to keep it on the road for now. Some people say to back up when unlocking and locking the hubs, but the OEM owners manual (well taken care of truck) says you only need to back to unlock them. Any idea on the "braking" feeling when locked. When traveling forward it's only pronounced in slow sharp turns, and the outer wheel feels like it's locking up. When backing it's the inside wheel. Having driven a Ford F-250 4X4 with auto lockers for work, I never encountered it this bad.

I think that I know what you are saying about the braking feeling. I noticed that on my Ford 250 also the other day when I was on bare pavement. I needed to use 4WD to get up a small hill on my yard when the grass was wet. When I pulled out onto the driveway and made a sharp turn, it felt like I had slammed on the brakes.

The Isuzu 4WD really should not be used on dry pavement.

Are all four of your tires the same size? I am struggling to find a solution for your issues that doesn't involve replacing the current hubs. One year at Moab, one of the rigs blew two tires one day. The owner bought two new tires in town that were a size larger as the owner was intending to go to the larger size. It was a disaster. The transfer case could not deal with the two ends of the vehicle running at different speeds.

BTW, the changeover from auto to manual hubs will probably take less time than it will take to try to service the current auto hubs.

All 4 tires are he same size, 245-75-16 (stock is 245-70-16 I believe). Front right is a little more worn than the left, but the overall wear is even. As far as driving dry, usually just up and down the alley behind my house, about 100 yards or so. If I have to replace the outer CV joints, then I'll probably make the switch to manual hubs. Going to grease them up good next weekend and put on 2pc boots then drive some steep fire roads a friend can get me on legally. Thanks for the info.

Did you resolve your vibration issue???

From the description, the likely culprits are tires out of balance, alignment, and CV/u-joint issues.

Thanks John. Not yet, but I haven't driven it much in the last month. The outer boots are cracked, so I'm betting that's it. Next on the list is outer cv joints and manual hubs.

Hope you resolve the problem soon...