http://www.therangerstation.com/forums/showthread.php?t=16
do a little reading here, may be able to get the spindle lock nuts conversion for cheaper.......and that ford body parts place is just for the spindle nuts at 55 bucks.....insane..
if you run oversize tires, get ready to learn about wheelbearing's and keeping the lock nuts tight.
the fun part is getting the locknuts tight on themselves(200-250ft lbs) with out crushing your bearings with preload or spining the lock ring tab over on the spindle and cutting the threads to shit or snaping the pin on the inside lock ring.......and once again overloading your bearings...
One stupid trick I have found that helps but dose not cure the problem is to weld build up the tab on the lockring to fit better in the spindle snout key way.
I have pics of this Ill try and find them and post them later....
even with the build up I still have to use a spanner wrech I ground down to fit, to hold the inner locknut while trying to get the outter nuts tight to lock the assmebly.
I also recomend some thread locker of your choice on the lock nuts.
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As for driving with the hubs locked on the street with the t-case in 2wd,no problems at all for the hubs.This acutally puts less wear on the hub bearing,but more wear on everything else.(axle shaft ujoints,front diff etc etc)Also make sure your spindle bearings(there are caged needle bearing's in side the spindle snout that the axle stub shaft's ride on)are in good shape and lubed.as 60mph jaunts dry could cause some problems in theroy.
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If you get manul hubs and want the best of the best of what's out there for the ranger get the jeep hubs.they have a better "hub bearing".This bearing is in use anytime your hubs are unlocked.
heres a link to the tech board with part numbers
http://www.therangerstation.com/Magazine/May04/offroad.htm
ok enuff rambling for me