1992 Mighty Max Hubs Not Locking

[Geoff]

Hi all. My 1992 Mighty Max 4x4 won’t go into four wheel drive. The transfer case is shifting fine. I suspect the automatic locking hubs are failing. I took a peek at the driver’s side hub today. No obvious problems. I’ll check the passenger side tomorrow. The hubs appear to be purely mechanical (no vacuum lines). If I see no obvious problems on the passenger side hub, then I’ll tear down both sides completely, then clean and grease them. Is there anything else to check? It seems like a simple system but it’s my first time digging into it. Outside temperature is around 30F. I don’t think it’s cold enough to be a factor but worth noting. Thanks.

[geezer101]

I'm not a 4x4 guy but I've heard the locking hubs need a magic touch sometimes to get them to lock and/or unlock. Try driving it in reverse for a short run and then attempt to engage the hubs. They need to be actuated once in a while so they don't seize up. Other than that about the only thing that can cause engagement issues is rust or crud in them. Guys have a similar issue with being unable to disengage 4x4 as well - same solution, drive it a short stint in reverse...

[Geoff]

Thanks geezer, I’ll give that a try. Maybe I’ll head down the hill, out of the snow and into the dirt to play around.

-Geoff

[B-Line]

Auto hubs require you to drive in reverse for at least 2’ after engaging 4wd. Then drive forward and the lights in your dash will illuminate.

[Geoff]

Update:
I cleaned up the auto hubs but it didn’t solve the problem.

I installed AISIN FHM-002 manual hubs. They appear to work. I’ve only done a quick rip around the yard in the snow so far. Looks like AVM and Hulk have them too. The important numbers for my truck:

Spline count 28
PCD 88mm
Bolts 6

Hopefully I can put some miles on them this weekend. I’ll update if I find any issues.

-Geoff